CODEWITHSUNDEEP
javaswingevent-handlingawtactionlistener
Chamindu Sandakelum Gunawarden
Chamindu Sandakelum Gunawarden

Reputation: 39

ActionListener for muliple JButton instances

I got a problem when adding ActionListener to two JButtons in the following Code.

I want to print each 1 and 2 when I click on these two Buttons (b1,b2)

But I can only print 1 or 2.

Could you please give me a solution to fix this problem?

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

class CCCc extends JFrame implements ActionListener{
    JButton b1,b2;
    JTextField f1;

CCCc(){
    setSize(500,200);
    setDefaultCloseOperation(JFrame.EXIT_ON_CLOSE);
    setLocationRelativeTo(null);
    setResizable(false);
    f1=new JTextField();
    f1.setHorizontalAlignment(JTextField.RIGHT);
    add("North",f1);
    JPanel p1=new JPanel(new GridLayout(1,2));
    add(p1);

    b1=new JButton("1");    
    b1.addActionListener(this); 
    b2=new JButton("2");
    b2.addActionListener(this);
    p1.add(b1);
    p1.add(b2);

    setVisible(true);
}
public void actionPerformed(ActionEvent evt){
    String s=f1.getText();
    f1.setText(s+"1");
}
}

Upvotes: 2

Views: 226

Answers (3)

Govind Balaji
Govind Balaji

Reputation: 639

I think the case is You want to know on which JButton, the ActionEvent is triggered, And if it is b1, You have to join a "1" to the textfield else "2". If the case is the above, do the following:

public void actionPerformed(ActionEvent evt){
JButton temp=evt.getSource();
String s=f1.getText()+temp.getText();
f1.setText(s);
}

If the case is not the above, then I say Sorry

Upvotes: 1

Tom Hawtin - tackline
Tom Hawtin - tackline

Reputation: 147154

It's a bad idea to subclass classes, such as JFrame and Thread, unnecessarily. It's also a bad idea to implement interfaces inappropriately. (Thirdly, it's a bad idea to attempt to look at the source of an event and the command is nasty as well)

I suggest switching to an anonymous inner class for the listeners. You will notice you have common code for both buttons, so that can be factored into a method requiring only a single inner class. The variable holding "1" or "2" would usually be referenced via a final local field in the method enclosing the anonymous inner class. However, you could use a non-anonymous class with a field accessed in the usual way.

Upvotes: 5

Hovercraft Full Of Eels
Hovercraft Full Of Eels

Reputation: 285405

The ActionEvent parameter has much useful information that you can use including a reference to the button pressed -- via getSource() or to the button's text via `getActionCommand(). So you can simply get the actionCommand from the ActionEvent and use it:

public void actionPerformed(ActionEvent evt){
    String s=f1.getText();
    f1.setText(s+ evt.getActionCommand());
}

Upvotes: 2

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