Java Video Tutorial 22
In this part of the Java Video Tutorial, I continue building your knowledge on how to use Java Swing. I actually broke this tutorial into 2 pieces. It will continue in part 23 of this series.
I cover a new GUI listener called the ChangeListener. I also introduce check boxes, radio buttons, groups, borders and sliders.
The code for both tutorials follows the video below.
If you haven’t seen part 1 it is here Java Video Tutorial.
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Code From the Video
import javax.swing.*;
import java.awt.event.*;
// New event listener that monitors changing values for components
import javax.swing.event.ChangeEvent;
import javax.swing.event.ChangeListener;
// Allows me to format the numbers
import java.text.NumberFormat;
// Allows me to edit borders on panels
import javax.swing.border.*;
public class Lesson22 extends JFrame{
JButton button1;
JLabel label1, label2, label3;
JTextField textField1, textField2;
JCheckBox dollarSign, commaSeparator;
JRadioButton addNums, subtractNums, multNums, divideNums;
JSlider howManyTimes;
double number1, number2, totalCalc;
public static void main(String[] args){
new Lesson22();
}
public Lesson22(){
// Define the size of the frame
this.setSize(400, 400);
// Opens the frame in the middle of the screen
this.setLocationRelativeTo(null);
// Define how the frame exits (Click the Close Button)
this.setDefaultCloseOperation(JFrame.EXIT_ON_CLOSE);
// Define the title for the frame
this.setTitle("My Third Frame");
// The JPanel contains all of the components for your frame
JPanel thePanel = new JPanel();
// ---------------------------------------------------------
// Create a button with Click Here on it
button1 = new JButton("Calculate");
// Create an instance of ListenForEvents to handle events
ListenForButton lForButton = new ListenForButton();
// Tell Java that you want to be alerted when an event
// occurs on the button
button1.addActionListener(lForButton);
thePanel.add(button1);
// How to add a label --------------------------
label1 = new JLabel("Number 1");
thePanel.add(label1);
// How to add a text field ----------------------
textField1 = new JTextField("", 5);
thePanel.add(textField1);
// How to add a label --------------------------
label2 = new JLabel("Number 2");
thePanel.add(label2);
// How to add a text field ----------------------
textField2 = new JTextField("", 5);
thePanel.add(textField2);
// How to add checkboxes ------------------------
dollarSign = new JCheckBox("Dollars");
commaSeparator = new JCheckBox("Commas");
thePanel.add(dollarSign);
// By putting true in here it is selected by default
thePanel.add(commaSeparator, true);
// Creates radio buttons with default labels
addNums = new JRadioButton("Add");
subtractNums = new JRadioButton("Subtract");
multNums = new JRadioButton("Multiply");
divideNums = new JRadioButton("Divide");
// Creates a group that will contain radio buttons
// You do this so that when 1 is selected the others
// are deselected
ButtonGroup operation = new ButtonGroup();
// Add radio buttons to the group
operation.add(addNums);
operation.add(subtractNums);
operation.add(multNums);
operation.add(divideNums);
// Create a new panel to hold radio buttons
JPanel operPanel = new JPanel();
// Surround radio button panel with a border
// You can define different types of borders
// createEtchedBorder, createLineBorder, createTitledBorder
// createLoweredBevelBorder, createRaisedBevelBorder
Border operBorder = BorderFactory.createTitledBorder("Operation");
// Set the border for the panel
operPanel.setBorder(operBorder);
// Add the radio buttons to the panel
operPanel.add(addNums);
operPanel.add(subtractNums);
operPanel.add(multNums);
operPanel.add(divideNums);
// Selects the add radio button by default
addNums.setSelected(true);
// Add the panel to the main panel
// You don't add the group
thePanel.add(operPanel);
// How to create a slider ----------------
label3 = new JLabel("Perform How Many Times?");
thePanel.add(label3);
// Creates a slider with a min value of 0 thru 99
// and an initial value of 1
howManyTimes = new JSlider(0, 99, 1);
// Defines the minimum space between ticks
howManyTimes.setMinorTickSpacing(1);
// Defines the minimum space between major ticks
howManyTimes.setMajorTickSpacing(10);
// Says to draw the ticks on the slider
howManyTimes.setPaintTicks(true);
// Says to draw the tick labels on the slider
howManyTimes.setPaintLabels(true);
// Create an instance of ListenForEvents to handle events
ListenForSlider lForSlider = new ListenForSlider();
// Tell Java that you want to be alerted when an event
// occurs on the slider
howManyTimes.addChangeListener(lForSlider);
thePanel.add(howManyTimes);
this.add(thePanel);
this.setVisible(true);
// Gives focus to the textfield
textField1.requestFocus();
}
private class ListenForButton implements ActionListener{
// This method is called when an event occurs
public void actionPerformed(ActionEvent e){
// Check if the source of the event was the button
if(e.getSource() == button1){
// getText returns a String so you have to parse it
// into a double in this situation
try{
number1 = Double.parseDouble(textField1.getText());
number2 = Double.parseDouble(textField2.getText());
}
catch(NumberFormatException excep){
// JOptionPane displays a popup on the screen
// (parentComponent, message, title, error icon)
// Error Icons: WARNING_MESSAGE, QUESTION_MESSAGE, PLAIN_MESSAGE
JOptionPane.showMessageDialog(Lesson22.this, "Please Enter the Right Info", "Error", JOptionPane.ERROR_MESSAGE);
System.exit(0); // Closes the Java app
}
if(addNums.isSelected()) { totalCalc = addNumbers(number1, number2, howManyTimes.getValue());
} else if(subtractNums.isSelected()) { totalCalc = subtractNumbers(number1, number2, howManyTimes.getValue());
} else if(multNums.isSelected()) { totalCalc = multiplyNumbers(number1, number2, howManyTimes.getValue());
} else { totalCalc = divideNumbers(number1, number2, howManyTimes.getValue()); }
// If the dollar is selected in the checkbox print the number as currency
if(dollarSign.isSelected()) {
// Defines that you want to format a number with $ and commas
NumberFormat numFormat = NumberFormat.getCurrencyInstance();
JOptionPane.showMessageDialog(Lesson22.this, numFormat.format(totalCalc), "Solution", JOptionPane.INFORMATION_MESSAGE);
}
// If the comma is selected in the checkbox print the number with commas
else if(commaSeparator.isSelected()) {
// Defines that you want to format a number with commas
NumberFormat numFormat = NumberFormat.getNumberInstance();
JOptionPane.showMessageDialog(Lesson22.this, numFormat.format(totalCalc), "Solution", JOptionPane.INFORMATION_MESSAGE);
} else {
JOptionPane.showMessageDialog(Lesson22.this, totalCalc, "Solution", JOptionPane.INFORMATION_MESSAGE);
}
}
}
}
// Implements ActionListener so it can react to events on components
private class ListenForSlider implements ChangeListener{
@Override
public void stateChanged(ChangeEvent e) {
// Check if the source of the event was the button
if(e.getSource() == howManyTimes){
label3.setText("Perform How Many Times? " + howManyTimes.getValue() );
}
}
}
public static double addNumbers(double number1, double number2, int howMany){
double total = 0;
int i = 1;
while(i <= howMany){
total = total + (number1 + number2);
i++;
}
return total;
}
public static double subtractNumbers(double number1, double number2, int howMany){
double total = 0;
int i = 1;
while(i <= howMany){
total = total + (number1 - number2);
i++;
}
return total;
}
public static double multiplyNumbers(double number1, double number2, int howMany){
double total = 0;
int i = 1;
while(i <= howMany){
total = total + (number1 * number2);
i++;
}
return total;
}
public static double divideNumbers(double number1, double number2, int howMany){
double total = 0;
int i = 1;
while(i <= howMany){
total = total + (number1 / number2);
i++;
}
return total;
}
}
nice video, if possible please upload some tutorial for layout’s
(ie. layout managers, split panes etc), how to create website type layouts in swing etc etc…
I’ll cover all of the other layout managers in the next few tutorials
nice video
Thank you 🙂
good effort
keep moving forward
Thank you 🙂
Hey,
Is there a difference between import javax.swing.*; and import javax.swing.event.*;?
I thought the * is a wildcard, but NetBeans won’t load the .event class if I only type in javax.swing.*;
Thanks!
You are supposed to use the most exact imports possible. I normally just let the IDE pick the right imports for me and don’t think about it. I guess NetBeans doesn’t do that for some reason?
Hi,
I just wanted to say, that I truly appreciate the way you explain why you are doing the code the way that you do. Also, I have heard a lot of different tutorials on Youtube, and could barely make out what they were saying; heavy accent. In any case, keep up the good work.
Thank You,
Vola
Thank you Vola 🙂 I’m very happy that you enjoy the videos. I plan to make many more.