不使用paint清除JFrame（Graphics g）

Question

I am trying to clear all of the contents of a JFrame so I can display something else. I don't want to use the paint(Graphics g) method because I am trying to clear the screen from within a timer and I'm unable to use

clearRect( int , int , int , int )

This is what I have already tried but the IDE gives an error and it doesn't clear the screen.

EDIT: my new code

    JFrame frame = new JFrame("...");
/*...*/

Timer timer = new Timer(5000, new RemoveContentsTask(frame));
timer.start();

/*...*/

public abstract class RemoveContentsTask implements Runnable {

private JFrame frame;

public RemoveContentsTask(JFrame frame) {
    this.frame = frame;
}

public void actionPerformed(ActionEvent evt) {
    frame.getContentPane().removeAll();


     System.out.println("Timer"); 
    }
}

Answer 1

1. You should be using a javax.swing.Timer instead of java.util.Timer to make sure you are honoring the single thread nature of Swing and making your updates within the EDT.
2. In the context of you question, this.getContentPane().removeAll() , this is referring to the instance of TimerTask

Instead you should try something more like...

import javax.swing.Timer;
/*...*/

JFrame frame = new JFrame("...");
/*...*/

Timer timer = new Timer(5000, new RemoveContentsTask(frame));
timer.start();

/*...*/

public class RemoveContentsTask implements Runnable {

    private JFrame frame;

    public RemoveContentsTask(JFrame frame) {
        this.frame = frame;
    }

    public void actionPerformed(ActionEvent evt) {
        frame.getContentPane().removeAll();
    }
}

Take a look at Concurrency in Swing for more details