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[java] Canvas issues

Started by phaelax Aug 23, 2006 at 3:35 AM 0 replies 3.4k views

Original Post

Aug 23, 2006 at 3:35 AM

All I'm doing is drawing some boxes onto a Canvas that can be dragged with the mouse. Since it flickers when i move them I wanted to use double buffering. Here's part of the class.


public class DisplayCanvas extends Canvas implements MouseInputListener
{
    private BufferStrategy buffer;
    private ArrayList objects = new ArrayList();
    private DisplayObject selectedObject = null;
    

    public DisplayCanvas()
    {
        this.createBufferStrategy(1);
        buffer = this.getBufferStrategy();
        
        this.addMouseListener(this);
        this.addMouseMotionListener(this);
    }

When I try to set the number of buffers to anything higher than 1, I get this error when trying to run the program: java.lang.IllegalStateException: Component must have a valid peer Not entirely sure what it means and I couldn't really find anything about it other than the docs said its thrown if the canvas isn't displayable.

blow

Aug 23, 2006 at 4:39 AM

U have this prob becouse you create bufferStrategy before that this component is add to container.
Try this:

public void addNotify(){   super.addNotify();   this.createBufferStrategy(2);   buffer = this.getBufferStrategy();}

So only when your add this compunent u create a byfferstrategy

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