Android Development Tutorial 3
In this part of my Android Development Tutorial, I will build an Android user interface.
I cover how to do numerous things: How to use the Android Visual Layout Editor, How to edit the GUI layout by editing the XML, How to use TextView, EditText and the SeekBar, How to catch events, How to save the apps state with onSaveInstanceState(), How to get values from components and how to change the values. The video and code below will teach you all you need to start making apps.
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Special Note
I have received many questions about the lines:
private static final String TOTAL_BILL = “TOTAL_BILL”;
private static final String CURRENT_TIP = “CURRENT_TIP”;
private static final String BILL_WITHOUT_TIP = “BILL_WITHOUT_TIP”;and then also lines:
billBeforeTip = savedInstanceState.getDouble(BILL_WITHOUT_TIP);
tipAmount = savedInstanceState.getDouble(CURRENT_TIP);
finalBill = savedInstanceState.getDouble(TOTAL_BILL);and also lines:
outState.putDouble(TOTAL_BILL, finalBill);
outState.putDouble(CURRENT_TIP, tipAmount);
outState.putDouble(BILL_WITHOUT_TIP, billBeforeTip);What I think is confusing everyone is the final in
private static final String TOTAL_BILL = “TOTAL_BILL”;
The value isn’t stored in TOTAL_BILL, TOTAL_BILL stores the name for the key that is associated with value. These are key value pairs. I should have pointed that out better.
Then when putDouble(String key, double value) is called it inserts a double value into the Bundle, and replaces the value for the given key.
I hope that clears that up. Sorry about any confusion.
If you are having trouble with the SeekBar
If your app is crashing when you use the seekbar it is because I don’t except commas in the price. Make sure you enter a period before the change amount and you should have anymore crashes. Sorry about that.
Code From the Video
Here is the whole Android App Package available for download!
Below is the code changes made to make this Android unser interface
activity_crazy_tip_calc.xml
<RelativeLayout xmlns:android="http://schemas.android.com/apk/res/android"
xmlns:tools="http://schemas.android.com/tools"
android:layout_width="match_parent"
android:layout_height="match_parent"
android:paddingBottom="@dimen/activity_vertical_margin"
android:paddingLeft="@dimen/activity_horizontal_margin"
android:paddingRight="@dimen/activity_horizontal_margin"
android:paddingTop="@dimen/activity_vertical_margin"
tools:context=".CrazyTipCalc" >
<TextView
android:id="@+id/billTextView"
android:layout_width="wrap_content"
android:layout_height="wrap_content"
android:layout_alignParentLeft="true"
android:layout_alignParentTop="true"
android:layout_marginLeft="14dp"
android:layout_marginTop="14dp"
android:text="@string/bill_text_view" />
<!-- android:ems defines the width of the EditText box -->
<EditText
android:id="@+id/billEditText"
android:layout_width="wrap_content"
android:layout_height="wrap_content"
android:layout_marginLeft="16dp"
android:layout_toRightOf="@+id/billTextView"
android:ems="5"
android:inputType="numberDecimal"
android:text="@string/bill_edit_text" >
<requestFocus />
</EditText>
<TextView
android:id="@+id/tipTextView"
android:layout_width="wrap_content"
android:layout_height="wrap_content"
android:layout_alignBottom="@+id/billTextView"
android:layout_marginLeft="15dp"
android:layout_toRightOf="@+id/billEditText"
android:text="@string/tip_text_view" />
<EditText
android:id="@+id/tipEditText"
android:layout_width="wrap_content"
android:layout_height="wrap_content"
android:layout_above="@+id/finalBillTextView"
android:layout_marginLeft="18dp"
android:layout_toRightOf="@+id/tipTextView"
android:ems="4"
android:inputType="numberDecimal"
android:text="@string/tip_edit_text" />
<TextView
android:id="@+id/finalBillTextView"
android:layout_width="wrap_content"
android:layout_height="wrap_content"
android:layout_alignLeft="@+id/finalBillEditText"
android:layout_below="@+id/billEditText"
android:layout_marginTop="14dp"
android:text="@string/final_bill_text_view" />
<EditText
android:id="@+id/finalBillEditText"
android:layout_width="wrap_content"
android:layout_height="wrap_content"
android:layout_alignRight="@+id/tipEditText"
android:layout_below="@+id/finalBillTextView"
android:ems="5"
android:inputType="numberDecimal"
android:text="@string/final_bill_edit_text" />
<TextView
android:id="@+id/changeTipTextView"
android:layout_width="wrap_content"
android:layout_height="wrap_content"
android:layout_alignBottom="@+id/finalBillTextView"
android:layout_alignLeft="@+id/billTextView"
android:text="@string/change_tip_text_view" />
<!-- android:progress="15" defines the default for the SeekBar -->
<SeekBar
android:id="@+id/changeTipSeekBar"
android:layout_width="match_parent"
android:layout_height="wrap_content"
android:layout_alignLeft="@+id/changeTipTextView"
android:layout_alignTop="@+id/finalBillEditText"
android:layout_marginTop="14dp"
android:layout_toLeftOf="@+id/tipTextView"
android:progress="15" />
</RelativeLayout>
strings.xml
<?xml version="1.0" encoding="utf-8"?>
<resources>
<string name="app_name">CrazyTipCalc</string>
<string name="action_settings">Settings</string>
<string name="bill_text_view">Bill</string>
<string name="bill_edit_text">0.0</string>
<string name="tip_text_view">Tip</string>
<string name="tip_edit_text">.15</string>
<string name="final_bill_text_view">Final Bill</string>
<string name="final_bill_edit_text">0.0</string>
<!-- END OF FIRST PART -->
<string name="change_tip_text_view">Change Tip</string>
</resources>
CrazyTipCalc.java
package com.newthinktank.crazytipcalc;
import android.os.Bundle;
import android.app.Activity;
import android.text.Editable;
import android.text.TextWatcher;
import android.view.Menu;
import android.widget.EditText;
import android.widget.SeekBar;
import android.widget.SeekBar.OnSeekBarChangeListener;
public class CrazyTipCalc extends Activity {
// Constants used when saving and restoring
private static final String TOTAL_BILL = "TOTAL_BILL";
private static final String CURRENT_TIP = "CURRENT_TIP";
private static final String BILL_WITHOUT_TIP = "BILL_WITHOUT_TIP";
private double billBeforeTip; // Users bill before tip
private double tipAmount; // Tip amount
private double finalBill; // Bill plus Tip
EditText billBeforeTipET;
EditText tipAmountET;
EditText finalBillET;
@Override
protected void onCreate(Bundle savedInstanceState) {
super.onCreate(savedInstanceState);
setContentView(R.layout.activity_crazy_tip_calc); // Inflate the GUI
// Check if app just started, or if it is being restored
if(savedInstanceState == null){
// Just started
billBeforeTip = 0.0;
tipAmount = .15;
finalBill = 0.0;
} else {
// App is being restored
billBeforeTip = savedInstanceState.getDouble(BILL_WITHOUT_TIP);
tipAmount = savedInstanceState.getDouble(CURRENT_TIP);
finalBill = savedInstanceState.getDouble(TOTAL_BILL);
}
// Initialize the EditTexts
billBeforeTipET = (EditText) findViewById(R.id.billEditText); // Users bill before tip
tipAmountET = (EditText) findViewById(R.id.tipEditText); // Tip amount
finalBillET = (EditText) findViewById(R.id.finalBillEditText); // Bill plus tip
// SECOND PART ---------------
// Initialize the SeekBar and add a ChangeListener
tipSeekBar = (SeekBar) findViewById(R.id.changeTipSeekBar);
tipSeekBar.setOnSeekBarChangeListener(tipSeekBarListener);
// ---------------------------
// Add change listener for when the bill before tip is changed
billBeforeTipET.addTextChangedListener(billBeforeTipListener);
}
// Called when the bill before tip amount is changed
private TextWatcher billBeforeTipListener = new TextWatcher(){
@Override
public void afterTextChanged(Editable arg0) {
// TODO Auto-generated method stub
}
@Override
public void beforeTextChanged(CharSequence arg0, int arg1, int arg2,
int arg3) {
// TODO Auto-generated method stub
}
@Override
public void onTextChanged(CharSequence arg0, int arg1, int arg2,
int arg3) {
try{
// Change the billBeforeTip to the new input
billBeforeTip = Double.parseDouble(arg0.toString());
}
catch(NumberFormatException e){
billBeforeTip = 0.0;
}
updateTipAndFinalBill();
}
};
// Update the tip amount and add tip to bill to
// find the final bill amount
private void updateTipAndFinalBill(){
// Get tip amount
double tipAmount = Double.parseDouble(tipAmountET.getText().toString());
// The bill before tip amount was set in billBeforeTipListener
// Get the bill plus the tip
double finalBill = billBeforeTip + (billBeforeTip * tipAmount);
// Set the total bill amount including the tip
// Convert into a 2 decimal place String
finalBillET.setText(String.format("%.02f", finalBill));
}
// Called when a device changes in some way. For example,
// when a keyboard is popped out, or when the device is
// rotated. Used to save state information that you'd like
// to be made available.
protected void onSaveInstanceState(Bundle outState){
super.onSaveInstanceState(outState);
outState.putDouble(TOTAL_BILL, finalBill);
outState.putDouble(CURRENT_TIP, tipAmount);
outState.putDouble(BILL_WITHOUT_TIP, billBeforeTip);
}
// ---- END OF FIRST PART ----
// ---- SECOND PART ----------
// SeekBar used to make a custom tip
private SeekBar tipSeekBar;
private OnSeekBarChangeListener tipSeekBarListener = new OnSeekBarChangeListener(){
@Override
public void onProgressChanged(SeekBar arg0, int arg1, boolean arg2) {
// Get the value set on the SeekBar
tipAmount = (tipSeekBar.getProgress()) * .01;
// Set tipAmountET with the value from the SeekBar
tipAmountET.setText(String.format("%.02f", tipAmount));
// Update all the other EditTexts
updateTipAndFinalBill();
}
@Override
public void onStartTrackingTouch(SeekBar arg0) {
// TODO Auto-generated method stub
}
@Override
public void onStopTrackingTouch(SeekBar arg0) {
// TODO Auto-generated method stub
}
};
// ---- END OF SECOND PART ----------
@Override
public boolean onCreateOptionsMenu(Menu menu) {
// Inflate the menu; this adds items to the action bar if it is present.
getMenuInflater().inflate(R.menu.crazy_tip_calc, menu);
return true;
}
}
AndroidManifest.xml
<?xml version="1.0" encoding="utf-8"?>
<manifest xmlns:android="http://schemas.android.com/apk/res/android"
package="com.newthinktank.crazytipcalc"
android:versionCode="1"
android:versionName="1.0" >
<uses-sdk
android:minSdkVersion="8"
android:targetSdkVersion="17" />
<application
android:allowBackup="true"
android:icon="@drawable/ic_launcher"
android:label="@string/app_name"
android:theme="@style/AppTheme" >
<activity
android:name="com.newthinktank.crazytipcalc.CrazyTipCalc"
android:label="@string/app_name" >
<intent-filter>
<action android:name="android.intent.action.MAIN" />
<category android:name="android.intent.category.LAUNCHER" />
</intent-filter>
</activity>
</application>
</manifest>
170 Responses to “Android Development Tutorial 3”
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Hi, Absolutely loving the Android tuts, thanks so much – keep them coming….
Secc
I have many more in the works. I’m glad you are enjoying them. I think they will tend to be long at around 20 to 25 minutes. I’ll pack them with information. I hope to make an app in each tutorial that follows to keep it interesting.
Hello. Dereck: I went through the tutorial and it show up and disappeared the first time. I erased the entire tutorial and started over. The .15 doesn’t appear when the app opens. The seek bar doesn’t work, but the calculations do work. I stepped through the program to look at the tip. The tip does work. It allows me to type in a different tip amount. But the seek bar doesn’t work. How could i fix that?
Good job on the Tutorial.
Thank you 🙂
Have you tried running the complete package I provide.
this guy is damn good, you opened up my brain.
thanks
Thank you 🙂 I’m very happy that I could help out.
Brilliant tutorial, nicely presented ..looking forward to your next Android tut !!
Thank you 🙂 I’m going to do my best in this tutorial series to make them interesting
I’m very happy that you begin android tutorials. I think it is the best course that you ever made from teaching prespective. You cover a wide range of things,you explain everything both theoritical and practical and you develop useful applications.
You are a master,keep up this way.
Thank you very much 🙂 I really want this series to completely teach everything. I think the need for programmers that can program for Android devices will continue to grow for some time. I hope I’ll be able to help
Hi Derek, are you familiar with PLC programming?
Sorry, but I haven’t touched PLC for some time
Hi , Derek Thank you so much . Great stuff btw .
I noticed that there’s a link for downloadable source code , which is great .
I asked you for that lately , so thank you for taking that into consideration .
Keep it up
You are the man !
You are the reason that the code is there. I always do my best to handle all requests. That was a good idea by the way 🙂
Hi Derek,
Thank You for these wonderful tutorials.
Keep up the great work. 🙂
You’re very welcome 🙂 Thank you for taking the time to show your appreciation
Hi Derek, I’m new to your android course (lets face it, is not a “tutorial” is a whole class!) and I’m very glad that I came upon it. I already subscribed to your channel and hoked up with your videos. thank you for taking the time and effort to share you vast knowledge.
Regards from Argentina.
Hi Gaston, I hope you enjoy the Android tutorial. I will do my best to cover everything in regards to Android. I plan on just making one app after another until everyone is satisfied. Thank you for taking a look at my little website 🙂
It’s not a ‘little’ website anymore Derek !!
It is getting quite large I agree 🙂
Hi Derek loving your tutorials and the way you explain things.
Have one slight problem maybe you could help me with. I’ve downloaded your code and everything works fine on the emulator
and a actual device running 4.2.2. However if I try running it on a another device that has 4.0.3, everytime i touch the seekbar the i get the “Unfortunately. CrazyTipCalc has stopped.” message.
How do I view errors, when running apps on the phone, in eclipse.
Thanks for your time
That is strange. The logcat should show errors for the emulator and any Android device connected. You could try this app which can be used to look at your phones error log https://play.google.com/store/apps/details?id=ukzzang.android.app.logviewer&hl=en
Hi again Derek, sorry to be a bother.
Thanks for your help and quick reply.
Just thought I’d let you know what I’ve found and maybe see if you have any ideas why this happens.
I used this code to test(within onCreate method) after seeing the error NumberFormatException : Invalid Double :-
EditText test = (EditText) findViewById(R.id.editText1);
test.setText(String.format(“%.02f”, Double.parseDouble(tipAmountET.getText().toString())));
On the device running 4.2.2 the test textfield displays 0.15, however on the device running 4.0.3 the same textfield displays 0,15. From this it is clear the comma is causing the problem when formatting.
Thanks again for your help.
Thank you for bringing that to my attention. As the tutorial continues, I’ll cover how to make sure your app works on numerous devices. I have been holding back on that so far because I want to cover all the basics first. There is much work to do to make apps that run on 60% of devices in the world, but I’ll get through it eventually
I’ve had the same problem trying to get the app to run on my htc sensation.
It turns out the problem is with the locale your device is set to. If you’re from europe (as i am) your most likely to have a “,” as a number separator instead of a “.” This causes problems with setting the text and the code errors out.
This is what i did to solve this problem.
Instead of
tipAmountET.setText(String.format("%.02f", tipAmount));i do
NumberFormat formatter = NumberFormat.getInstance(Locale.US);tipAmountET.setText(formatter.format(tipAmount));
and apply this everytime you set text via code. hope this helps
Thank you very much for helping out 🙂 I greatly appreciate that!!!
I suffer from the same problem it really helps thanks a lot
Hi Derek i really love the tutorials
i am having problem running the application on emulator i keep on getting this error Unfortunately, Tipcal has stopped. what should i do about it?
Look in the logcat console. In there it will point out all the errors. Feel free to post them here and I’ll take a look
Below is the Error i got from logcat
06-14 14:18:21.485: E/AndroidRuntime(804): java.lang.RuntimeException: Unable to start activity ComponentInfo{com.wilfred.tipscal/com.wilfred.tipscal.TipcalActivityMainActivity}: java.lang.ClassCastException: android.widget.TextView cannot be cast to android.widget.SeekBar
If you catch the ClassCastException that should handle that issue for now. I didn’t focus to much time on exception handling at this point because I wanted to teach as many different topics at once in each video. Sorry about the confusion
Hey,
I tried running the .apk on my Nexus 4 and it crashes everytime i try to open the app :s.
It worked okay when i used the nexus4 emulator.
Any ideas?
If you connect and run while connected to Eclipse the LogCat will show errors. What does it show there?
An error has occurred. See error log for more details.
java.lang.NullPointerException.
Hi Derek
Best ever tutorial I came across with full code support.
Only thin is when I tried to open “res-values-strings” Eclipse throws above error.
Have done something wrong?
Thanks
Arif
Thank you very much 🙂 Check out the code in the package I provide for download. A NullPointerException occurs when an object isn’t initialized. There is probably a typo some place
Hi Derek,
Great work! Thank you!
I had the same “NullPointerException” when trying to follow this episode.
The cause was related to the ContentView’s name. Since I am using API 19 as opposed to your API 17, ADT creates two XML layout files (fragment_crazy_tip_calc.xml and activity_crazy_tip_calc.xml).
In your code, you are setting the ContentView to the value “R.layout.activity_crazy_tip_calc” (as this is the file that holds the RelativeLayout).
However, with the new version, it should be set to “R.layout.fragment_crazy_tip_calc” (or whatever is the file that actually contains the RelativeLayout).
Thank you once again.
Best regards,
B
Thank you 🙂 Yes I’m going to have to do a tutorial Very Soon on the changes to the ADT
Thank you! Looking forward to it.
Best regards,
B
Incredible! I (a total noob at android) was getting the same error. This was the fix for me!
Thank B! And thanks Derek for all the awesome tuts.
You’re very welcome 🙂
When I opened the CrazyTipCalc.java in the code it said (twice) “R cannot be resolved to a variable” any suggestions?
Eclipse sometimes likes to add an “import android.R” statement at the top of your files that use resources, especially when you ask Eclipse to sort or otherwise manage imports. This will cause your make to break. Look out for these erroneous import statements and delete them.
What if you have TWO editText’s? I want to validate both inputs, basically they are ranges and I want to update a textView based on the changes they made, for example:
public void onTextChanged(CharSequence s, int start, int before,
int count) {
// TODO Auto-generated method stub
try
{
//theFirst = Integer.parseInt(s.toString());
theFirst = Integer.parseInt(firstText.getText().toString());
theLast = Integer.parseInt(secondText.getText().toString());
if (theFirst > theLast)
{
updateLabel.setText(“You must flip your integers”);
}
else if (theFirst < 0)
{
updateLabel.setText("You cannot enter a negative number!");
}
guess = (theFirst + theLast) / 2;
updateLabel.setText("Did you think of " + guess + " ?");
} catch (NumberFormatException nfe)
{
updateLabel.setText("You must enter an integer! ");
}
All I am trying to do is, transfer my GUI JAVA in to ANDROID. But I am having trouble how to use this text handler in android, thank you for your time
Actually this is the whole thing so you can understand what I am doing. The problem is that, in my emulator when I enter the different ranges, it does nothing. BUT when I press on a button (like tooHigh or tooLow) the textView changes to “It appears you have changed your number!”
package com.bignerdranch.android.guessinggame;
import android.os.Bundle;
import android.app.Activity;
import android.text.Editable;
import android.text.TextWatcher;
import android.view.Menu;
import android.view.View;
import android.widget.Button;
import android.widget.EditText;
import android.widget.TextView;
import android.view.View.OnClickListener;
public class AlphaActivity extends Activity {
private static final String TO_BOX = “TO_BOX”;
private static final String FROM_BOX = “FROM_BOX”;
// private String updateGuess;
// private String update_label;
private int guess, theFirst, theLast;
//private int count;
private String update_text;
EditText firstText;
EditText secondText;
TextView updateLabel;
Button tooHighButton;
Button tooLowButton;
Button correctButton;
Button newGameButton;
@Override
protected void onCreate(Bundle savedInstanceState) {
super.onCreate(savedInstanceState);
setContentView(R.layout.activity_alpha);
if(savedInstanceState == null){
// Just started
theFirst = 0;
theLast = 100;
}
else
{
// App is being restored
theFirst = savedInstanceState.getInt(TO_BOX);
theLast = savedInstanceState.getInt(FROM_BOX);
}
//fromBox = (EditText) findViewById(R.id.firstText);
//toBox = (EditText) findViewById(R.id.secondText);
//fromBox.addTextChangedListener(fromBox);
//toBox.addTextChangedListener(toBox);
updateLabel = (TextView)findViewById(R.id.updateText);
firstText = (EditText)findViewById(R.id.firstText);
firstText.addTextChangedListener(fromBoxListener);
secondText = (EditText)findViewById(R.id.secondText);
secondText.addTextChangedListener(fromBoxListener);
tooHighButton = (Button)findViewById(R.id.guiTooHigh);
tooLowButton = (Button)findViewById(R.id.tooLowGui);
correctButton = (Button)findViewById(R.id.correctGui);
setButtonOnClickListeners();
}
private TextWatcher fromBoxListener = new TextWatcher()
{
@Override
public void afterTextChanged(Editable arg0) {
// TODO Auto-generated method stub
}
@Override
public void beforeTextChanged(CharSequence s, int start, int count,
int after) {
// TODO Auto-generated method stub
}
@Override
public void onTextChanged(CharSequence s, int start, int before,
int count) {
// TODO Auto-generated method stub
try
{
//theFirst = Integer.parseInt(s.toString());
theFirst = Integer.parseInt(firstText.getText().toString());
theLast = Integer.parseInt(secondText.getText().toString());
if (theFirst > theLast)
{
updateLabel.setText(“You must flip your integers”);
}
else if (theFirst < 0)
{
updateLabel.setText("You cannot enter a negative number!");
}
guess = (theFirst + theLast) / 2;
updateLabel.setText("Did you think of " + guess + " ?");
} catch (NumberFormatException nfe)
{
updateLabel.setText("You must enater an integer! ");
}
//updateLabel();
}
};
private void setButtonOnClickListeners(){
tooHighButton.setOnClickListener(new OnClickListener(){
public void onClick(View arg0) {
theLast = (guess – 1);
guess = (theFirst + theLast) / 2;
if (theFirst theLast)
{
updateLabel.setText(“It appears you changed your number!”);
} else
{
updateLabel.setText(“Did you think of ” + guess + ” ?”);
}
}
});
tooLowButton.setOnClickListener(new OnClickListener(){
@Override
public void onClick(View arg0) {
theFirst = (guess + 1);
guess = (theFirst + theLast) / 2;
if (theFirst theLast)
{
updateLabel.setText(“It appears you changed your number!”);
} else
{
updateLabel.setText(“Did you think of ” + guess + ” ?”);
}
}
});
correctButton.setOnClickListener(new OnClickListener(){
@Override
public void onClick(View arg0) {
updateLabel.setText(“Thank you for playing this game!”);
}
});
}
// private void updateLabel(){
//
// int currentFrom = Integer.parseInt(fromBox.getText().toString());
// int currentTo = Integer.parseInt(toBox.getText().toString());
//
//
// updateText.setText(“Did you think of ” + guess + ” ?”)
//
//
// }
@Override
public boolean onCreateOptionsMenu(Menu menu) {
// Inflate the menu; this adds items to the action bar if it is present.
getMenuInflater().inflate(R.menu.alpha, menu);
return true;
}
}
Any ideas?
Wait nevermind! This works! I was expecting it to work like JAVA, I was expecting to see the label to change when I press enter, but it automatically changes once I change the EditText
My app crashes as soon as I press a button?
package com.bignerdranch.android.guessinggame;
import android.os.Bundle;
import android.app.Activity;
import android.graphics.Color;
import android.text.Editable;
import android.text.TextWatcher;
import android.view.Menu;
import android.view.View;
import android.widget.Button;
import android.widget.EditText;
import android.widget.TextView;
import android.view.View.OnClickListener;
public class AlphaActivity extends Activity {
private static final String TO_BOX = “TO_BOX”;
private static final String FROM_BOX = “FROM_BOX”;
// private String updateGuess;
// private String update_label;
private int guess, theFirst, theLast, count;
//private int count;
private String update_text;
EditText firstText;
EditText secondText;
TextView updateLabel;
TextView currentGuessText;
Button tooHighButton;
Button tooLowButton;
Button correctButton;
Button newGameButton;
@Override
protected void onCreate(Bundle savedInstanceState) {
super.onCreate(savedInstanceState);
setContentView(R.layout.activity_alpha);
count = 0;
if(savedInstanceState == null){
// Just started
theFirst = 0;
theLast = 100;
}
else
{
// App is being restored
theFirst = savedInstanceState.getInt(TO_BOX);
theLast = savedInstanceState.getInt(FROM_BOX);
}
//fromBox = (EditText) findViewById(R.id.firstText);
//toBox = (EditText) findViewById(R.id.secondText);
//fromBox.addTextChangedListener(fromBox);
//toBox.addTextChangedListener(toBox);
updateLabel = (TextView)findViewById(R.id.updateText);
firstText = (EditText)findViewById(R.id.firstText);
firstText.addTextChangedListener(fromBoxListener);
secondText = (EditText)findViewById(R.id.secondText);
secondText.addTextChangedListener(fromBoxListener);
tooHighButton = (Button)findViewById(R.id.guiTooHigh);
tooLowButton = (Button)findViewById(R.id.tooLowGui);
correctButton = (Button)findViewById(R.id.correctGui);
setButtonOnClickListeners();
}
private TextWatcher fromBoxListener = new TextWatcher()
{
@Override
public void afterTextChanged(Editable arg0) {
// TODO Auto-generated method stub
}
@Override
public void beforeTextChanged(CharSequence s, int start, int count,
int after) {
// TODO Auto-generated method stub
}
@Override
public void onTextChanged(CharSequence s, int start, int before,
int count) {
// TODO Auto-generated method stub
try
{
//theFirst = Integer.parseInt(s.toString());
theFirst = Integer.parseInt(firstText.getText().toString());
theLast = Integer.parseInt(secondText.getText().toString());
if (theFirst > theLast)
{
updateLabel.setText(“You must flip your integers”);
}
else if (theFirst < 0)
{
updateLabel.setText("You cannot enter a negative number!");
}
guess = (theFirst + theLast) / 2;
updateLabel.setText("Did you think of " + guess + " ?");
} catch (NumberFormatException nfe)
{
updateLabel.setText("You must enater an integer! ");
}
}
};
private void setButtonOnClickListeners(){
tooHighButton.setOnClickListener(new OnClickListener(){
public void onClick(View arg0) {
theLast = (guess – 1);
guess = (theFirst + theLast) / 2;
if (theFirst <= theLast)
{
secondText.setText("" + theLast);
updateLabel.setText("Did you think of " + guess + " ?");
count++;
currentGuessText.setText("Current guess number is " + count);
currentGuessText.setTextColor(Color.BLUE);
} else
{
updateLabel.setText("It appears you changed your number!");
}
}
});
tooLowButton.setOnClickListener(new OnClickListener(){
@Override
public void onClick(View arg0) {
theFirst = (guess + 1);
guess = (theFirst + theLast) / 2;
if (theFirst <= theLast)
{
firstText.setText("" + theFirst);
updateLabel.setText("Did you think of " + guess + " ?");
count++;
currentGuessText.setText("Current guess number is " + count);
currentGuessText.setTextColor(Color.BLUE);
} else
{
updateLabel.setText("It appears you changed your number!");
}
}
});
correctButton.setOnClickListener(new OnClickListener(){
@Override
public void onClick(View arg0) {
updateLabel.setText("Thank you for playing this game!");
}
// I still need to remove action listeners
});
}
@Override
public boolean onCreateOptionsMenu(Menu menu) {
// Inflate the menu; this adds items to the action bar if it is present.
getMenuInflater().inflate(R.menu.alpha, menu);
return true;
}
}
What is the error in the logcat?
hi derek, sorry for bothering you, i’m having some problem with the code, is the same you put here but i feel more confortable implementing the interfaces, i’m having a numberformat exception only when i start the app and try to fill the bill edittext, but when i fill the tip first nothing happens, the app works normally, thanks for your attention, please let me know if you need the code.
I’m sorry if I didn’t explain this better. The idea behind making these videos was to cover as much as possible in each video. I didn’t catch all of the exceptions and other random things. You can make the numberformaterror go away by catching the exception. Sorry about that
Hi Derek (or anyone) i have a question:
why do we have to define
if(savedInstanceState == null){
036
037 // Just started
038
039 billBeforeTip = 0.0;
040 tipAmount = .15;
041 finalBill = 0.0;
***EDIT
Hi Derek (or anyone) i have a question:
why do we have to define
if(savedInstanceState == null){
036
037 // Just started
038
039 billBeforeTip = 0.0;
040 tipAmount = .15;
041 finalBill = 0.0;
because if the app is just booting shouldn’t it just get the default values from strings.xml?
Yes you could definitely do it that way. That is more then likely the preferred way.
Hi Derek, I saw your video and coded up the whole thing as you explained. Whenever i run it on my device(android 4.0.4), It says “Unfortunately, …Stopped Working”. I basically get AndroidRuntime.
Fatal Exception :MissingFormatWidthException -f.
What should i do?? Let me know if you need my code.
Never mind Derek, it Worked. Great tutorial by the way! 🙂
Thank you 🙂
Hi Derek, need some help.
I was designing an app that would collect data from user, store it somewhere online to allow access to this data to other users of the app. Since SQLite wont work in this case, can you suggest something??
A tutorial if possible on one such thing would be of tremendous help! 🙂
You need to create a web service. Then your android app could use a http client to connect to the web service to get your data. I’m thinking about covering that soon. I already talked a bit about a rest service later in the tutorial
Hi there!
Firstly, I just want to say thank you for your tutorials and source-code, it’s all excellently taught 🙂
Now, on to the issue I have 😛
Basically whenever I finish the app, I run into a major issue, where if I edit the bill value, the program crashes. I have pasted logcat below:
07-04 12:23:23.136: W/dalvikvm(8071): threadid=1: thread exiting with uncaught exception (group=0x40e4fac8)
07-04 12:23:23.146: E/AndroidRuntime(8071): java.lang.NumberFormatException: Invalid double: “”
The peculiar item is that your code runs perfectly fine, and I’ve compared our code and the main difference is only formatting, which leaves me slightly confused. Could you please advise what error I am making? (Mind you, I have no experience in Java, although I’ve done most of the C’s,so I’m a bit bewildered why I’m experiencing error!)
Thanks!
I should also clarify by saying on the device I’m testing on (Galaxy-S4) it prompts after the crash:
“Unfortunately, TipCalculator has stopped”;
Which is the main error I’m getting.
Nevermind!
It apparently fixed itself after I had entered text values for tipEditText and finalEditText. How peculiar, does it cause a zero error due to a null input?
Yes that is the reason for the crash. I should have stated in the video that the goal isn’t to make a perfectly working app, but instead to introduce as many Android capabilities as possible. A few exception handlers here and there will fix all the errors that might pop up. I don’t really have time to properly test the apps if I want to make these videos quickly. There is always something strange that will pop up like how people in some countries use commas instead of decimals in currency. I hope that makes sense
Awesome Tutorials, but I have a quick question about downloading the files from your site. When I do -> click on Import on Eclipse > Import from Existing Android Project > Finish, I get this Error “Invalid project Description” , Is there something I am doing wrong? How Do I run your downloaded code on my eclipse so I can run it on my droid? … I already asked this on youtube, not sure which you would see and respond to.
Thank you 🙂 To import a project File – Import – General – Existing projects into workspace – next – check Select root directory – Browse – Select my package and Finish
To run on device when you click run configuration then click and change the target to your Android device which is plugged into the computer.
I hope that helps
Derek
Hi. Small question: in the updateTipAndFinalBill function, why do you make new variables:
double tipAmount = Double.parseDouble(tipAmountET.getText().toString());
double finalBill = billBeforeTip + (billBeforeTip * tipAmount);
in stead of saving them to your already existing variables in
private double billBeforeTip; // Users bill before tip
private double tipAmount; // Tip amount
private double finalBill; // Bill plus Tip
? Is there a specific reason for this? In my opinion you are keeping things double (no pun intended), and not using the MVC model properly. Thanks for the videos btw!
Hi, I agree, but sometimes when I’m writing code I have to make a judgement call on whether writing unoptimized code sometimes makes it easier to understand what is going on. I always assume that advanced programmers such as yourself will spot the issue and optimize it, while true beginners will at least understand the basics of what I’m trying to teach.
I hope that makes sense?
yeah sure I understand now. I am only a beginning android developer so maybe there were some hidden tricks behind this i did not know of, that’s why i asked. Thanks for the reply.
Android is hard to understand in the beginning, but after you get past a few odd things it will make sense
I want to build an offline android Dictionary English-Nepali app where there is a database of the words and its corresponding word in other. And, whenever the word is given for search it points out to the nearest match. Can you please explain on how can I build this. Is there any readymade libraries for this?
Later on in my Android Video Tutorial, I show how to create a database and how to query it for information like translations. I also have a link to a SQLite tutorial on that page to help you. Tell me if you have any other questions.
ofkpwoe
Sir Derek Thanks a lot you have given Superb Lectures……
Thank you 🙂 i try to do my best.
thank you very much,brilliant tutorial.
Thank you very much 🙂 I’m glad you enjoyed it.
Great Tutorial!
Thank you 🙂
This is so great! It was a long time when I did programming. I thought I will not do it again because there’s so many languages and so many versions, and I thought mobile App development is complicated… until, I saw your videos. It’s so informative and for sure I will watch all of it. THANKS A LOT!
Thank you 🙂 I’m very happy that I could help.
Sorry to bother you Derek, but i’ trying to find what i did wrong when Eclipse block me with this error message on:
super.onSaveInstanceState(outState);
error message is: The method onSaveInstanceState(Bundle) is undefined for the type Object
i’m gona continu to check every line but if you have an idea and a couple of minutes to spare by writing something about that. that will be helpful. Thanks anyway for your work, it’s awesome.
Never mind, i was out of range declaring my methodes at the wrong place. Thanks anyway.
The french guy who enjoy your tutorials..
I’m glad you found the fix 🙂
shouldn’t the savedInsatanceState.getDouble(…) function be called in the onResume(…) function? because according to the Process Lifecycle when a background comes back to focus, onResume() in called.
Yes I didn’t cover that because I didn’t want to add additional confusion about that at the time. That may have been a mistake in hindsight?
Hey Derek,
I just finish the tutorial (added the SeekBar) today and when i tried it, it crashes my app. So i check the log and find an error about
tipAmountET.setText(String.format(“%.02f”, tipAmount));
The log said: java.lang.NumberFormatException: invalid double: “0,10”
I search about 30 min what i did wrong and finaly find out…
My computer local settings are french and we type our number with a semicolone instade a dot so for those foreigners who are following your tutorials dont forget to add the local value for the string format like so:
tipAmountET.setText(String.format(Locale.us, “%.02f”, tipAmount));
Thanks again for your time and your good work.
Alan
Thank you for pointing that out. I couldn’t figure out the problem for the longest time. I’ll put a note on the video.
Great tutorials, I just finished this video and have the app built upto the seek bar. I tried adding an additional listener for the tip amount so that if the user directly edits the tip amount instead of using the seek bar the final bill will adjust accordingly, however the app crashes when I change the tip amount, it’s definitely the listener I added – If I comment out the listener I added it doesn’t crash. It works if I only change the ones/hundreths place but if I change the 10/10nths place it crashes.
/** private TextWatcher tipAmountListener = new TextWatcher(){
@Override
public void afterTextChanged(Editable arg0) {
// TODO Auto-generated method stub
}
@Override
public void beforeTextChanged(CharSequence arg0, int arg1, int arg2,
int arg3) {
// TODO Auto-generated method stub
}
@Override
public void onTextChanged(CharSequence arg0, int arg1, int arg2,
int arg3) {
try {
tipAmount = Double.parseDouble(arg0.toString());
}
catch(NumberFormatException e){
tipAmount = 0.0;
}
updateTipAndFinalBill();
}
}; */
thank you very much for this turial Derek, I really learned a great deal. Theres just this one thing Im now sure about, in the method – updateTipAndFinalBill(). why did you have to declare the data type of the variables : tipAmount and finalBill. You already declared them as doubles at the beginning of the activity.
Sorry about the confusion. I was referring to local variables in those later functions and I made a judgement call to give them the same names as the global variables. In hind sight that was a bad idea, but technically it is still ok.
Great vid Derek. Can you please explain a bit more about the key value pair? Still kinda confused on where the values(i.e.tip) are stored and retrieved. Thanks
Basically we need a unique name for our keys. Normally I would use a name like com.newthinktank.total.bill. I then would create a shortened variable name that would refer to this long key. That way I get a unique name, but it will also be short and easy to use. So any place I type totalBill, com.newthinktank.total.bill would actually be there.
In this tutorial to try and simplify the idea I used private static final String TOTAL_BILL = “TOTAL_BILL”
It is just the key part of the key / value pair. We need this so that we can pass this data between activities. Does that help?
Hello Derek, I am therry pleased by your tutorials, everything is therry clear and you explain it all so good, that even a fool would understand.
I was wonderring if you would make a xamarin tutorial. Xamarin is an IDE which can be used for cross-platform programming using C#. It gives people an opportunity to make apps for Android, iOS, MacOS and Windows at the same time and if this is not enougth, it gives you the whole power of .NET
So If you will do this, you’ll probably get a VIP palace in heavan.
Thank you 🙂 I’m sorry, but I don’t expect to cover xamarin anytime soon. I prefer to make tutorials using free tools so that everyone can participate. Sorry about that.
i am watching you tutorals great tuts but i need some advice i was trying to make a calculator on my own its a big task for me but when i put the numbers in the graphical view and the number signs like +-=/ it gives me an error asking to use strings what can i do
i found out what i forgot silly me i watched the video again i forgot to add them to the string xml
Hi great tutorials.
Just curious, your function “onSaveInstanceState” whats its use? If I keep or remove this function from your tutorial I do not see any difference when I flip my phone or if I go to another program and return to this one… If I close the app the values are not saved with or without this function.
Yves
It is used to save data when an Activity loses focus. You’ll see many better explanations for its use as I create more complex apps.
Hey there, I’m really trying to figure this one out, checked my code against your code but I find my error nowhere.. Whenever I open the app on my phone, and I try to input something on the Bill amount the app crashes. If I try to put something in the Tip amount, then everything works correctly. But if I go to the bill amount from the beginning it just crashes… Can you spot the possible causes with this? I could copy paste part of the code if you’d like to see it, but I’m not sure if this will help.
Thanks for the tutorials, they’re great
I see other people had my same error, somewhere I just probably didn’t read those well enough. I believe exception handlers and other things will be added… Thanks!
Yes I didn’t focus on catching every possible error because I wanted to focus on the Android code specifically in the beginning. As the tutorial continues I spend a great deal of time covering exception handling and such.
The most common reason for the crashes is the use of commas in the bill. I didn’t expect people would enter commas. Sorry about that.
I love you’re tutorials.
But i have a problem. When i change the tip amount. It doesnt edit the final bil. The final bil stays the same. And i cant use the seekbar cuze when i try to my app crashes.
I saw your post above with the commas problem. So i copy all the files here above and the app stil didnt work any idea what the problem could be?
Thank you 🙂 The only reason I have seen that crashes the app is the comma issue. You can continue on with the tutorial. Through out the entire tutorial this seems to be the only circumstance in which there are errors. I’m sorry that I didn’t know about the comma issue 🙁
Hi,
I really liked the tutorial. One question on this blog as it appears in Chrome, though, is how do I select only the code without the line numbers in the samples? I think there’s a trick to using a table to do this, so that the line numbers would be a column by themselves. pastebin.com does it that way I think.
But that’s a small irritation. Keep up the great tutorials.
-Jay
Hi Jay,
Thank you 🙂 I’m glad you like the tutorials. To copy the code without the line numbers, put your mouse on the code and in the upper right hand corner 3 icons will appear. Click on the first one named View Source and the code will appear without line numbers.
I hope that helps
Derek
Derek,
The tutorials are incredibly easy to understand. I am very happy to have come across them when I did and I will no doubt watch the tutorials on OOD and Java Algorithms.
Sincerely,
Peter Baldwin
Hi Peter, Thank you very much 🙂 I’m glad they have helped
Hello Derek
Liked your fast paced tutorials covering many things in place.
Is there a website or something where I can find a categorized list of these tutorials?
Regards
Amjad
Thank you 🙂 at the top of my website if you click videos you’ll see a page devoted to android. On that page I have every video and descriptions for each. I hope that helps
Appreciate your reply to almost all the comments, so committed.
Thanks.
I try to do my best. Some times I get a bit backed up though.
Hey Derek, thanks so much for creating these. They are great! Quick question – is the data that you store in those 3 constants available once the application is closed, or only when it is paused? What would be the easiest way to permanently store data like this? I’m sure you’ve addressed this in later tutorials so feel free to direct me there. Thanks again!
You’re very welcome 🙂 I normally store a small amount of information in a file. If I need a larger group of information then I tend to use SQLite.
Hi Derek,
First of all “KUDOS” for this awesome series. I could have never thought that android programming would attract my fancy but thanks to your lectures! AWESOME!
I built the same app but without the seek bar functionality. Now when I am trying to run my code while opening the app and trying to delete the ‘0.0’ value (which is by default) in the EditText field of the Bill through the inbuilt keyboard to give it a new value , the app crashes saying “CrazyTipCalc” app is not responding.
I compared your code (minus the seek bar functionality) and it seems to be same.
Can you please help me with this ?
I answered your question on YouTube. Are you still having trouble with this?
Nope ! Thanks…I made the Text Watcher inside the onCreate method itself so I think the problem was there. I took it outside the method and it worked.
Hi, I felt like fiddling with it a little more than you demonstrated, and tried to figure out a way to update the final bill as you change the tip amount. I got as far as adding a change listener to the tip amount, but if you completely delete everything from the tip edit view (and leave not even a 0) it crashes.
I was thinking there may have been something wrong with my tipAmountListener:
// Called when the tip amount is changed
private TextWatcher tipAmountListener = new TextWatcher() {
@Override
public void afterTextChanged(Editable arg0) {
// TODO Auto-generated method stub
}
@Override
public void beforeTextChanged(CharSequence arg0, int arg1, int arg2,
int arg3) {
// TODO Auto-generated method stub
}
@Override
public void onTextChanged(CharSequence arg0, int arg1, int arg2,
int arg3) {
try {
// Change tipAmount to the new input
tipAmount = Double.parseDouble(arg0.toString());
}
catch(NumberFormatException e) {
tipAmount = 0.0;
}
updateTipAndFinalBill();
}
};
omg man you are the best teacher I’ve ever had =D thanks
Thank you very much 🙂 I appreciate you taking the time to tell me that.
You are the one who makes this really clear and simpler!!!
Like these videos!
Thank you very much 🙂 I do my best.
Very good!
Thanks!
So I followed the tutorial completely and eclipse reported no errors with any of the code. However, at the end when I attempted to run the app the emulator would crash instantly, every single time. I also made sure to leave hardware keyboard unchecked.
What is the error you saw in LogCat in Eclipse? I provide all the code. You can also import the whole package. Try that out. It is probably a typo.
Okay two things: First in the console log (which I’m assuming is LogCat) it says “Failed to allocate memory: 8”, it has a blank line, then it says “This application has requested Runtime to terminate in an unusual way.” Second I downloaded your whole package of crazytipcalc and I extracted it to my App_workspace folder (where eclipse has chosen as my project storing location) however I cannot figure out how to actually have it available to run in eclipse. I’m able to open up the .java file, but it won’t show up in my project explorer.
I cover how to install the newest Android tools here. That should solve that problem.
I followed the tutorial, but still trying to run either my version or the package you put out to download has the same result: Failure to allocate memory: 8
I have a tutorial on how to install the new Android tools. Have you seen it?
Derek – i just started with Android – your tutorials are fantastic. Thanks and keep up the great work.
Thank you very much 🙂 I’ll be making Android apps for most of the rest of the year.
Hi Derek. Very good videos on android apps. Please teach us one app which needs a server as well like WhatsApp.
Thank you 🙂 I’ll be covering how to set up a web service. I made a couple of tutorials on how to read from them. That will come out ASAP.
hi sir would you like to upload some tutorial about GPS Development???????
I will cover GPS and everything else I missed after I finish with my App Inventor tutorial. I did a ton of things with GPS in my App inventor tutorial.
hello sir,
i’m very interesting with your tutorial…i would like to learn simple code for creating a dictionary app…can you give me a simple source code of a dictionary app…
thank you
Thank you 🙂 Why not get that translation app done quickly? If you use App Inventor and the Google Translate API you could get it done by parsing the json data. I cover app inventor in my Android Development for Beginners tutorial.
Hi Derek,
Thank you for such a great android tutorial you have, i’m gonna go through all your android tutorial..
I have a problem though, when i run CrazyTipCalc as android application it always respond ‘Unfortunately, CrazyTipCalc has stopped.’
I use the latest ADT, and based on your ADT 26 tutorial.
These are my log cat :
04-14 23:34:46.002: W/dalvikvm(1263): threadid=1: thread exiting with uncaught exception (group=0xa4c41648)
04-14 23:34:46.002: E/AndroidRuntime(1263): FATAL EXCEPTION: main
04-14 23:34:46.002: E/AndroidRuntime(1263): java.lang.RuntimeException: Unable to start activity ComponentInfo{com.blabla.crazytipcalc/com.blabla.crazytipcalc.CrazyTipCalc}: java.lang.NullPointerException
04-14 23:34:46.002: E/AndroidRuntime(1263): at android.app.ActivityThread.performLaunchActivity(ActivityThread.java:2211)
04-14 23:34:46.002: E/AndroidRuntime(1263): at android.app.ActivityThread.handleLaunchActivity(ActivityThread.java:2261)
04-14 23:34:46.002: E/AndroidRuntime(1263): at android.app.ActivityThread.access$600(ActivityThread.java:141)
04-14 23:34:46.002: E/AndroidRuntime(1263): at android.app.ActivityThread$H.handleMessage(ActivityThread.java:1256)
04-14 23:34:46.002: E/AndroidRuntime(1263): at android.os.Handler.dispatchMessage(Handler.java:99)
04-14 23:34:46.002: E/AndroidRuntime(1263): at android.os.Looper.loop(Looper.java:137)
04-14 23:34:46.002: E/AndroidRuntime(1263): at android.app.ActivityThread.main(ActivityThread.java:5103)
04-14 23:34:46.002: E/AndroidRuntime(1263): at java.lang.reflect.Method.invokeNative(Native Method)
04-14 23:34:46.002: E/AndroidRuntime(1263): at java.lang.reflect.Method.invoke(Method.java:525)
04-14 23:34:46.002: E/AndroidRuntime(1263): at com.android.internal.os.ZygoteInit$MethodAndArgsCaller.run(ZygoteInit.java:737)
04-14 23:34:46.002: E/AndroidRuntime(1263): at com.android.internal.os.ZygoteInit.main(ZygoteInit.java:553)
04-14 23:34:46.002: E/AndroidRuntime(1263): at dalvik.system.NativeStart.main(Native Method)
04-14 23:34:46.002: E/AndroidRuntime(1263): Caused by: java.lang.NullPointerException
04-14 23:34:46.002: E/AndroidRuntime(1263): at com.blabla.crazytipcalc.CrazyTipCalc.onCreate(CrazyTipCalc.java:65)
04-14 23:34:46.002: E/AndroidRuntime(1263): at android.app.Activity.performCreate(Activity.java:5133)
04-14 23:34:46.002: E/AndroidRuntime(1263): at android.app.Instrumentation.callActivityOnCreate(Instrumentation.java:1087)
04-14 23:34:46.002: E/AndroidRuntime(1263): at android.app.ActivityThread.performLaunchActivity(ActivityThread.java:2175)
04-14 23:34:46.002: E/AndroidRuntime(1263): … 11 more
04-14 23:34:46.002: W/ActivityManager(467): Force finishing activity com.blabla.crazytipcalc/.CrazyTipCalc
The key error is NullPointerException. This is triggered when an object has the value of null. Did you by any chance type a comma in the tip part. That causes an error that I wasn’t expecting.
I am also seeing this error. It looks like the latest eclipse SDK is creating the Android App with fragments that breaks getting a handle to edit controls using findViewById() in onCreate() of the app. Fragments seem to make coding overly complicated.
I’ll make a tutorial very soon that will explain what changed recently with Android.
Hello Derek,
Best tutorials I’ve found online for Android Development.
I just had a question on an error I’m having. When I initialize the SeekBar in CrazyTipCalc.java, the id for the seek bar cannot be found. Here’s the xml for the seekbar
And heres the java I’m using to initialize the SeekBar.
tipSeekBar = (SeekBar) findViewById(R.id.changeTipSeekBar);
When I type the above code, the id changeTipSeekBar cannot be found. When I changed the id in the graphical layout, it asked me if I wanted to update all references and I said yes.
Do you know what the problem is?
Thanks,
Paul
Here’s the xml.
SeekBar
android:id=”@+id/changeTipSeekBar”
android:layout_width=”match_parent”
android:layout_height=”wrap_content”
android:layout_alignLeft=”@+id/changeTipTextView”
android:layout_alignRight=”@+id/finalBillEditText”
android:layout_below=”@+id/changeTipTextView”
android:progress=”15″
I found that if I go in and initialize another string in strings.xml and then set that string equal to android:text=”@string/newString” in the seek bar xml then it fixes the error.
And for the tipEditText, if I set this to .15 using the tip_edit_text String then there’s trouble initializing the tipEditText. It has the same issue where it can’t find the id for the tipEditText. If I set the tip_edit_text String to 0.0, then there’s no trouble finding the id when initializing the tipEditText
Great I’m glad you fixed it 🙂
Hi Paul,
Thank you 🙂 Sorry I couldn’t get to your problem quicker. I’m glad you found a fix and posted it.
REALLY REALLY GOOD TUTORIAL SIMPLE AND GOOD THANK YOU..
AND A REALLY GOOD TEACHER
Thank you very very much 🙂
Hi Derek!
Thank u soooooo much for ur tutorial! It really helps soooooo much!! I got a small problem that is hard to explain and I can’t understand it.
So I know the key-value pair concept. For example String type TOTAL_BILL is the key of double type finalBill. So when u do “putDouble(TOTAL_BILL, finalBill);” the value which key is TOTAL_BILL will be replaced by finalBill, right?
So my question is before u actually use this key-value pair, u must in somewhere pre-set the key-value pair in ur code. But I don’t see u did that. So how could Android know that ur TOTAL_BILL is associated with finalBill, not something else?
In other words,
TOTAL_BILL(key) -> finalBill(value),
CURRENT_TIP(key) -> tipAmount(value),
BILL_WITHOUT_TIP(key) -> billBeforeTip(value),
Those association must be setup in Java code, but I can’t find where u did this.
I really appeciate for any idea about my question.
finalBill gets assigned the stored value here finalBill = savedInstanceState.getDouble(TOTAL_BILL)
outState.putDouble(TOTAL_BILL, finalBill) stores the value in finalBill to the key value pair.
I hope that helps 🙂
I think I understand it. Thanks!! Go keep watching ur tutorial!
Hey there, thank you so much and as soon as i am able i will buy you more than a cup of coffee! In the mean time I was wondering if you could help with some questions I have I apologize in advance because I did not read all the comments above to make sure you haven’t already answered and this may not be the best arena for you to answer my questions but i do see the value for you and others for the answers being here. With that being said here it is, im getting a warning Description Resource Path Location Type
No grammar constraints (DTD or XML Schema) referenced in the document. AndroidManifest.xml /freecreditapp/bin line 27 XML Problem. i have been playing around with some things and applying the tip app in somewhat of a different fashion as im sure you have noticed and I will happily explain further if we could google hangout sometime on air or off. then next would be when i go to upload a second version to the play store im getting apk errors and it fails not letting me upload a new version so i chanced a few things and attempted to upload a new application this didnt work either I know im forgetting something simple but having trouble figuring out what thank you so much for your time and consideration
You are very welcome 🙂 I’m happy if I can help.
To get rid of that error make sure you have this at the top of your manifast file < ?xml version="1.0" encoding="utf-8"?>
If that doesn’t get rid of it, Right click on the error and delete it. It probably won’t come back.
To update an app you upload a new apk file but make sure you have incremented the android:versionCode and android:versionName attributes in the element of the manifest file.
I hope that helps 🙂
Hello Derek,
Thank you for your tutorials. They are great.
My program works perfect except the listener part. I am getting errors in my logcat due to it and application gets crashed. When i comment out the
tipSeekBar = (SeekBar) findViewById(R.id.changeTipseekBar);
and
billbeforetipET.addTextChangedListener(billBeforeTipListner);
lines my program works fine. Else, it doesn’t. I have typed in exactly the same code you have used. But still the listener part is not working. In the previous comments you have mentioned that we need to include exceptions for the program to work correctly. As i am a beginner i couldn’t solve this error. I went through your successive tutorials but you haven’t mentioned about the exceptions. Could you kindly help me out with this by either providing me codes or links to get this resolved.
Thanks in advance.
What errors are you getting? It may be an issue in the layout files?
Great tutorials Derek. I usually dont write comments, but your tutorials are way too good!
Thank you so much, I am glad i found your channel/website. I will be waiting for more of your videos!
Thank you very much 🙂 I do my best to make the best tutorials that I can. i’m glad you like them.
Thank you for the awsome tutorials.
my main class always says extends ActionBarActivity while yours just says extends Activity.
That is the only difference i found between mine and your code and once i changed it to yours it worked, and before the app would just crash. Do you know why? and how can i make it so it automatically just says extends Activity like yours.
thanks
Thank you 🙂 If you set your minimum API in the manifest to 11 that will go away.
Hi derek,
First of all, thank you SO much for these tutorials. I’m a beginner and i wanna know that if i follow all your tutorials, do i need to read and learn more from developer.android.com??
or are your tutorials enough?
And and i ran your code, without the seek bar. Exactly the same, infact i even copy pasted your code to check if i did a mistake, even then when i run the app, even if i try to remove the 0.0 from bill, the app crashes. Any idea why?
Thank you so much again!
Hi,
I cover a lot while making one app after another in this tutorial series. My newest Android tutorial will finish up everything I missed here like interface design and such.
What error do you see in the logcat panel for this app. The most common occurs if a comma is entered in the amount.
I get the same exception.
FATAL EXCEPTION: main
java.lang.NumberFormatException: Invalid double: “”
at java.lang.Double.parseDouble(Double.java.295) and so on…
As soon as I edit the Bill EditText content, my app crashes.
You get that error if you enter a comma instead of a decimal for a price.
I really appreciate the android tutorials! Except for when using this one i keep having a problem with the seekbar. I always get a NumberFormatException error. He can’t parse 0,2 for example to a double. He can only do that for 0.2 and it seems that my seekbar outputs his data with “,” any ideas how to solve this?
Thanks!
You can’t use commas in anyway for the tip amount. Sorry I didn’t expect people to use commas.
Hi,
Just want to ask on how to restore the R.java file? I’ve already encountered this 3 times and its frustrating to recreate everything again. Hope you could address this concern.
Thanks.
David
Try running a clean on the project, or under the Project menu is an option build automatically.