button problem

[abrar alvi]

hi, help me with this code....

import java.awt.event.ActionEvent;
import java.awt.event.ActionListener;
import java.util.logging.Level;
import java.util.logging.Logger;
import javax.swing.*;


public class EventDemo implements ActionListener{
JButton b1;
void go(){
    JFrame frame=new JFrame("my first applet");
b1=new JButton("my buttton");
b1.setName("click");
b1.setText("click me");
b1.addActionListener(this);
frame.add(b1);
frame.setDefaultCloseOperation(JFrame.EXIT_ON_CLOSE);
frame.setSize(200, 200);
frame.setVisible(true);
}
    @Override
    public void actionPerformed(ActionEvent e) {
        b1.setText("you clicked me");
    }
    public static void main(String[] args) {
       EventDemo test=new EventDemo();
       test.go();
    }
 
}

Output:

before clicking:



after clicking:




Problem:

after clicking i want to rest the button setText() to click me (again) after 2 seconds...

[Michael Dunn]

use a Timer

[Tony Docherty]

More explicitly use a javax.swing.Timer.

The reason you are better off using the swing Timer as opposed to the java.util.Timer is the swing timer runs the action event listeners on the Event Dispatch Thread so you can directly manipulate swing components.

[abrar alvi]

thanks i will try out...

[abrar alvi]

yes i used the Timer and the button got freeze for the required time but the problem how do i set

the old text (i.e "click me") again.


this is my modified code:

 
@Override  
    public void actionPerformed(ActionEvent e) {  
        b1.setText("you clicked me");  // i need to set "click me" again after this action have been performed
  Timer timed=new Timer(50, this);
        timed.start();

    }  

[Tony Docherty]

I thought you wanted to wait 2 seconds and not 50 milliseconds!

You need to pass an ActionListener into the Timer's constructor.
You are passing 'this' which means when the timer completes it will call this objects actionPerformed method which creates and starts a new timer again and so on and so on.
BTW This is a good place to use an anonymous inner class ie

    Timer myTimer = new Timer(2000, new ActionListener() {
            @Override
            public void actionPerformed(ActionEvent arg0) {
                // TODO add your set button text code here
                }
        });

By default Timers repeat every n milliseconds so before starting it you should call

myTimer.setRepeats(false);

[Campbell Ritchie]

Tony Docherty wrote: . . .This is a good place to use an anonymous inner class . . .

As a general rule, I like anonymous classes, provided you only use them once each. I do not like addActionListener(this), because it often denotes failure to use proper object design.

[Tony Docherty]

Campbell Ritchie wrote:I do not like addActionListener(this), because it often denotes failure to use proper object design.

Agreed, especially when the actionPerformed method has a list of if-else statements which take some action depending on which component triggered the event.

[abrar alvi]

Tony Docherty wrote:I thought you wanted to wait 2 seconds and not 50 milliseconds!

You need to pass an ActionListener into the Timer's constructor.
You are passing 'this' which means when the timer completes it will call this objects actionPerformed method which creates and starts a new timer again and so on and so on.
BTW This is a good place to use an anonymous inner class ie

    Timer myTimer = new Timer(2000, new ActionListener() {
            @Override
            public void actionPerformed(ActionEvent arg0) {
                // TODO add your set button text code here
                }
        });

By default Timers repeat every n milliseconds so before starting it you should call

myTimer.setRepeats(false);

thanks... my code is working well now....

but as i am a beginner i am having some confusion with the Timer.....

can you share some good and easy article for it to learn....


thanks...

[Campbell Ritchie]

I am pretty sure there is something about Timers in the Java Tutorials. Yes, try here.

[Campbell Ritchie]

Tony Docherty wrote: . . . when the actionPerformed method has a list of if-else statements . . .

And if that isn’t non‑object‑oriented design, I don’t know what is!

[abrar alvi]

thank you guys for the help......

i have got a new problem with the above code...

problem code :

public class EventDemo implements ActionListener {
   JButton b1;

    void go() {
        JFrame frame = new JFrame("Change text of button");
        b1 = new JButton("my buttton");
        b1.setText("CLICK ME");
        b1.addActionListener(this);
        frame.add(b1);
        frame.setDefaultCloseOperation(JFrame.EXIT_ON_CLOSE);
        frame.setSize(200, 200);
        frame.setVisible(true);
    }

    @Override

public void actionPerformed(ActionEvent e) {

        b1.setText("BUTTON CLICKED");
        Timer myTimer = new Timer(1000, new ActionListener() {

            @Override
            public void actionPerformed(ActionEvent arg) {

                b1.setText("CLICK ME (newly set)");// i want to get the above original b1.setText("CLICK ME") 
                                                                         which i have set in go() here.
                count++;
            }
        });

        myTimer.setRepeats(false);
        myTimer.start();

    }

help me....

[Campbell Ritchie]

And what goes wrong? We can’t help without more details.

[abrar alvi]

Campbell Ritchie wrote:And what goes wrong? We can’t help without more details.

i have written the problem as comment in my code


(i.e i want to get the original b1.setText("CLICK ME") which i have set in go() in the Timer class actionPerformed())...

thank you

[Michael Dunn]

it seems to work OK as is (by setting the same string), but if you want the original

in class's actionPerformed add this line
final String originalText = b1.getText();//<----place above line below
b1.setText("BUTTON CLICKED");

now in the timer's actionPerformed, change
b1.setText("CLICK ME (newly set)");
to
b1.setText(originalText);

[abrar alvi]

Thanks Michael Dunn

Now my code is running perfect, i really love this forum and you guys.....


Can you explain me why have you made String originalText as final....


thanks

[Michael Dunn]

> Can you explain me why have you made String originalText as final....

remove the word 'final', recompile, see what happens.

[abrar alvi]

Michael Dunn wrote:> Can you explain me why have you made String originalText as final....

remove the word 'final', recompile, see what happens.

yes i removed and tried it gives the follwoing error message:

Exception in thread "AWT-EventQueue-0" java.lang.RuntimeException: Uncompilable source code - local variable originalText is accessed from within inner class; needs to be declared final
at EventDemo$1.actionPerformed(EventDemo.java:41)
at javax.swing.Timer.fireActionPerformed(Timer.java:312)
at javax.swing.Timer$DoPostEvent.run(Timer.java:244)
at java.awt.event.InvocationEvent.dispatch(InvocationEvent.java:251)
at java.awt.EventQueue.dispatchEventImpl(EventQueue.java:721)
at java.awt.EventQueue.access$200(EventQueue.java:103)
at java.awt.EventQueue$3.run(EventQueue.java:682)
at java.awt.EventQueue$3.run(EventQueue.java:680)
at java.security.AccessController.doPrivileged(Native Method)



"local variable originalText is accessed from within inner class; needs to be declared final" please explain me this line...


thanks

[Darryl Burke]

abrar alvi wrote:"local variable originalText is accessed from within inner class; needs to be declared final" please explain me this line...

Read all about it here.