Attaching A Single Action Listener To All Buttons
I have a program with many buttons, all of which will be performing the same function. I was wondering if there was a way to attach a single listener to all existing JButtons in the program.
Solution 1:
Something like:
import java.awt.*;
import java.awt.event.*;
import javax.swing.*;
import javax.swing.border.*;
public class CalculatorPanel extends JPanel
{
private JTextField display;
public CalculatorPanel()
{
Action numberAction = new AbstractAction()
{
@Override
public void actionPerformed(ActionEvent e)
{
display.setCaretPosition( display.getDocument().getLength() );
display.replaceSelection(e.getActionCommand());
}
};
setLayout( new BorderLayout() );
display = new JTextField();
display.setEditable( false );
display.setHorizontalAlignment(JTextField.RIGHT);
add(display, BorderLayout.NORTH);
JPanel buttonPanel = new JPanel();
buttonPanel.setLayout( new GridLayout(0, 5) );
add(buttonPanel, BorderLayout.CENTER);
for (int i = 0; i < 10; i++)
{
String text = String.valueOf(i);
JButton button = new JButton( text );
button.addActionListener( numberAction );
button.setBorder( new LineBorder(Color.BLACK) );
button.setPreferredSize( new Dimension(50, 50) );
buttonPanel.add( button );
KeyStroke pressed = KeyStroke.getKeyStroke(text);
InputMap inputMap = button.getInputMap(JComponent.WHEN_IN_FOCUSED_WINDOW);
inputMap.put(pressed, text);
button.getActionMap().put(text, numberAction);
}
}
private static void createAndShowUI()
{
// UIManager.put("Button.margin", new Insets(10, 10, 10, 10) );
JFrame frame = new JFrame("Calculator Panel");
frame.setDefaultCloseOperation( JFrame.EXIT_ON_CLOSE );
frame.add( new CalculatorPanel() );
frame.pack();
frame.setLocationRelativeTo( null );
frame.setVisible(true);
}
public static void main(String[] args)
{
EventQueue.invokeLater(new Runnable()
{
public void run()
{
createAndShowUI();
}
});
}
}
The Action
will get the source object from the Event so that it knows which button was clicked.
If you need to use if/else logic in your Action, then you should be creating a separate Action. Don't force code into one Action if it doesn't belong.
Solution 2:
Simply add the ActionListener to the buttons.
For the specific action depending on the source, you can use what I wrote or use ActionCommands (which basically links certain components to 'commands' that are sent to the ActionListener on an event).
Here's a little example:
public class MyClass implements ActionListener
{
JButton button1;
JButton button2;
JButton button3;
public MyClass()
{
button1 = new JButton();
button2 = new JButton();
button3 = new JButton();
button1.addActionListener(this);
button2.addActionListener(this);
button3.addActionListener(this);
}
@Override
public void ActionPerformed(ActionEvent e)
{
//do stuff
//if you want to do something depending on the button pressed
//check the source
if (e.getSource() == button1)
{
//do stuff
}
}
}
Solution 3:
You Could...
Create a single instance of the ActionListner and apply it to all the buttons
You Could...
Make use if the Actions API, which will allow you to create a self contained ActionListerner, which also includes the details to configure the buttons as well.