Question

Can anyone tell me why does this timer run only once?

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

public class TimerTest implements ActionListener{

    private Robot r;
    private Timer t;
    private int i;

    public TimerTest(){     
        i = 0;  
        try {
            r = new Robot();
        } catch (AWTException e) {
            // TODO Auto-generated catch block
            e.printStackTrace();
        }       
        t = new Timer(1000, this);  
        t.setRepeats(true);
        t.start();  
    }

    public static void main(String [] args){
        new TimerTest();        
    }

    @Override
    public void actionPerformed(ActionEvent arg0) {
        i++;
        System.out.println("Action..." + i);        
    }

The funny thing is that, if I decrease the delay in the Timer to just 100, it works as expected. And what’s even funnier is that if I delete the code in which I initialize the Robot, it doesn’t work at all, the program terminates as soon as I run it.

I’ve tried this on Windows 7 and on Ubuntu (although on Ubuntu I couldn’t use the Robot at all, since I get an exception. Something related to rights, maybe).

Answer 1

Your main is processed so the program stops. You can test it by using this code, adding it to TimerTest()

JFrame testFrame = new JFrame();
testFrame.setVisible(true);
testFrame.setDefaultCloseOperation( JFrame.EXIT_ON_CLOSE );

That JFrame keeps your main not from finshing, when you close the Frame the TimerTest ends. Which concludes your main which causes the main to finsh. Ending the program and stoping your swing timer.