One action listener for multiple JButtons?

[surk23]

My program has 8 JButtons and 1 JTextField. Each button should change the text in the text field to something different. I started out having an action listener for each button but i would like to link all the buttons to just 1 action listener and have it recognise which button has been pressed to execute the correct action. any ideas on how this could be done?

[NormR1]

Create an instance of an object that implements ActionListener.
Add that object as each button's action listener.

To recognize which button, use the Event getSource() method.

[NormR1]

Deleted

[JamesCherrill]

JButtons, kike all JComponents have a really useful but much neglected property called "clientProperty", which is a hashtable into which you can put whatever key/vlaue pairs you want with putClientProperty(key, value), and retrieve the values with getClientProperty(key).
Depending on how your buttons are supposed to behave you can use this to store a String, or a object, or whatever else you need to do the appropriate thing for each button. This avoids the huge if/else/else... structure you would end up with if you have to test the source for being equal to each button in turn.

[tong1]

The following code may help you:

import javax.swing.*;
import java.awt.event.*;
import java.awt.*;

public class MultiButtons extends JFrame implements ActionListener{
	JButton btn[] = new JButton[3];  // define and allocate for the array of 3 buttons
	String colorName[]={"RED","BLUE","GREEN"};  // the string on each button
	Color color[] = {Color.red, Color.blue, Color.green}; // Color array
    Container container;
    
    
	public MultiButtons(){
	JPanel p = new JPanel(); // create a sub container to have 3 buttons
	for (int i=0; i<btn.length;i++){ // create button and add ActionListener for each button.
		btn[i]= new JButton(colorName[i]);
		btn[i].addActionListener(this);
		btn[i].putClientProperty( "JButton.buttonType", "roundRect" ); // setup clientProperty, as JamesCherrill indicated.
		p.add(btn[i]);// put each button into the sub container
                  }
	container= getContentPane(); // The JFrame has the default layout manager: BorderLayout
	container.add(p, BorderLayout.NORTH); // the subcontainer holding 3 buttons is placed in the NORTH area
	container.setBackground(color[0]); // initial background is red in color
	setSize(400,200);
	setVisible(true);
	}	
	
	public void actionPerformed(ActionEvent e){ // the ActionListener monitoring 3 buttons.  
		for (int i=0; i<btn.length;i++) // using for loop to scan buttons
		if (btn[i]== e.getSource()){ // the button[i] is being pressed
		container.setBackground(color[i]); // re-set background color accordingly
		break;
		}
		}
	public static void main(String args[]){
	MultiButtons mb= new MultiButtons();
	mb.setDefaultCloseOperation(2);
	}
}

e.g.
In my machine, the line code:
btn.putClientProperty( "JButton.buttonType", "roundRect" );
was not working
I tried putClientProperty() in different way. It ended with no changes in buttons' apprearence at all.

[NormR1]

Couple of comments:
Emb.setDefaultCloseOperation(2); // what is the 2 here? Use defined constants not their value

was not working

Please explain.

The idea of using a components property table is to save info for that component that can be retrieved later. For example if you wanted to save a color. Use a name/key like: "MyColor" and say a reference to a Color object: theColor
putClientProperty( "MyColor", theColor ); // save the color

Later you get the color object back by:
Color theColor = (Color)getClientProperty("MyColor"); // get what I saved earlier

[tong1]

line 36 is not correct.
The correct code:

mb.setDefaultCloseOperation(JFrame.EXIT_ON_CLOSE);// The value of the defined constant JFrame.EXIT_ON_CLOSE is 3

Thank you, NormR1 for your coments.

was not working

I will have a close look at tutorial on the issue of putClientProperty.