How to paint an invisible JFrame elsewhere?

Question

I want to paint the contents of a JFrame onto another frame. Currently, I only get it to work if the JFrame is visible.
Is there a way to paint a hidden JFrame?

Additional info:
In my project I need to be able to rotate and scale windows. I do not want to write my own window-api, so I thought I might be able to just paint JFrames or similar container classes in a rotated way (which the Graphics2D-API supports perfectly well). It would be awesome to be able to use standard JFrames for that, but a custom frame extending a JFrame would also be OK..

public class JFTest extends JFrame {
    private JFrame frameToPaint = null;

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

    public JFTest () {
        // some basic initialization
        super ("Container");
        setDefaultCloseOperation (JFrame.EXIT_ON_CLOSE);
        setExtendedState (JFrame.MAXIMIZED_BOTH);
        add (new JPanel () {
            @Override public void paintComponent (Graphics g) {
                super.paintComponent (g);
                // painting the child frame's contents onto this frame
                if (frameToPaint != null) frameToPaint.getRootPane().paintAll (g);
            }
        });
        setVisible (true);

        // initializing some test-frame that will get painted onto the container
        frameToPaint = new JFrame ("child");
        frameToPaint.setSize (200, 100);
        frameToPaint.add (new JLabel ("test"));
        frameToPaint.addComponentListener (new ComponentAdapter() {
            @Override public void componentResized (ComponentEvent e) { repaint (); }
            @Override public void componentHidden  (ComponentEvent e) { repaint (); }
        });

        // magic line. an invisible frame will not get painted! why??
        frameToPaint.setVisible (true);
    }
}

I don't know what you mean by *"paint an invisible JFrame elsewhere"* [sic] and I *really* don't think it's the solution to your problem. Now: you *can* display fully translucent windows in Java **but** there are gotchas. On OS X Apple JVMs, it has always been supported (even on old OS X versions: works back on OS X 10.4 for sure). On Windows, there are non-official APIs (whose methods may change / disappear) since JVM 1.6.0_22 if I'm not mistaken. Otherwise you can use JNA to get any level of transparency you want on Windows / OS X / Linux / etc. JNA comes with a transparency example. — TacticalCoder, Nov 04 '11 at 11:34
I want to get the graphical contents of a frame without having to make the frame visible for the user. — bit, Nov 04 '11 at 11:40
@bit It sounds like you want some sort of buffer to paint in before copying to a frame. In that case, look into the use of a [BufferStrategy](http://download.oracle.com/javase/7/docs/api/java/awt/image/BufferStrategy.html). Or create some BufferedImage or [VolatileImage](http://download.oracle.com/javase/7/docs/api/java/awt/image/VolatileImage.html) through a GraphicsConfiguration and paint on that before copying. — G_H, Nov 04 '11 at 12:10

score 2 · Answer 1 · answered Nov 04 '11 at 13:55

2

Hint 1: JFrame's setDefaultLookAndFeelDecorated(false)/setUndecorated(true) might be of use for a window without caption and borders;

Hint 2: as setGlassPane/setLayeredPane/setOpaque(false) might be of use for a second "layer".

answered Nov 04 '11 at 13:55

Joop Eggen

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score 2 · Answer 2 · answered Nov 04 '11 at 14:55

I want to get the graphical contents of a frame without having to make the frame visible for the user

The Screen Image class should help. Although I think it will only work for the "content pane" of the frame and not the entire frame (with the title bar and borders) unless you use a decorated frame.

score 1 · Answer 3 · edited May 23 '17 at 11:55

1) you have to use proper LayoutManager, not setSize() or setBounds()

2) if is there null LayoutManager used then Container returns any size after setVisible(true);

3) if is there used proper LayoutManager, then Container return its Size after call pack();, in other hands this container couldn't be visible on the screen ( meaning setVisible(true); )

4) JComponents must to returns PrefferedSize for example

How to paint an invisible JFrame elsewhere?

3 Answers3

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