Question

In a short method, I hide a JFrame using setVisible(false).
Then I take a screenshot and restore the JFrame with setVisible(true).

After made visible again, the window is supposed to show a different picture than before (lets say a part of that screenshot taken).

The problem is that after setVisible(true) is called, the window is flashed with the old content for a split second before paintComponent is called and the updated state is drawn.

I could probably workaround this in an ugly way, but I wanted to know if there are better solutions.

Thanks in advance for any help

edit: While preparing an example, I noticed that the effect was hardly ever observable when not using transparency like I do in my program. Should probably have mentioned that. Here is what I came up with:

import java.awt.Color;
import java.awt.Dimension;
import java.awt.Graphics;
import java.awt.Toolkit;

import javax.swing.JFrame;
import javax.swing.JPanel;

import com.sun.awt.AWTUtilities;
public class Test {

    static boolean flag = false;
    static Dimension scrSize = Toolkit.getDefaultToolkit().getScreenSize();

    public static void main(String[] args) throws InterruptedException {
        JFrame frame = new JFrame();
        frame.setUndecorated(true);
        AWTUtilities.setWindowOpaque(frame, false);  //draw on a transparent window
        frame.setSize(scrSize.width, scrSize.height);
        frame.setContentPane(new JPanel() {
            protected void paintComponent(Graphics g) 
            {
                if (Test.flag) {
                    g.setColor(Color.RED);
                    g.drawRect(50, 50, scrSize.width - 100, scrSize.height - 100);
                }
                else {
                    g.setColor(Color.GREEN);
                    g.fillOval(50, 50, scrSize.width - 100, scrSize.height - 100);
                }
            }
        });
        frame.setVisible(true); //green oval shown
        Thread.sleep(1000);
        frame.setVisible(false);
        flag = true; // next draw produces red rectangle
        Thread.sleep(1000);
        frame.setVisible(true); // before the next draw, 
                                // you can see a flash of the green oval
    }

}

Answer 1

I realise that this answer is being suggested a year after the question was asked, but I had a similar problem and of course researched a bit before I tried to solve it. For anyone who comes across this question, try disposing your window / frame before you pack and make it visible.