java混合主动和被动渲染

Question

im developing an application that has two JPanels. The first JPanel is used as a drawing board and the second is used as a property/settings panel. So the drawing board should use active rendering and the second one passive. They are both added to a JFrame.

I've been reading about active rendering in java but i've noticed that JPanel doesnt support createBufferStrategy. Does this mean i need to use a canvas? The problem with canvas is that it is not a container so i can't add components to it. I could also use the JFrame buffered strategy (but then i would have to fix the position offset due to the title?).. Could i use a JPanel to actively render on but still have the second JPanel use passive rendering?

Answer 1

Here is some example of combining "passive" Swing components and active animation:

public static void main ( String[] args )
{
    JFrame frame = new JFrame ();

    JPanel view = new JPanel ( null );
    view.setPreferredSize ( new Dimension ( 500, 500 ) );
    frame.add ( view );

    JButton button1 = new JButton ( "Button 1" );
    button1.setBounds ( 10, 10, 100, 40 );
    button1.setOpaque ( false );
    view.add ( button1 );

    Animator animator = new Animator ();
    animator.setBounds ( 0, 0, 500, 500 );
    view.add ( animator );

    JButton button2 = new JButton ( "Button 2" );
    button2.setBounds ( 390, 450, 100, 40 );
    button2.setOpaque ( false );
    view.add ( button2 );

    frame.setResizable ( false );
    frame.setDefaultCloseOperation ( JFrame.EXIT_ON_CLOSE );
    frame.pack ();
    frame.setLocationRelativeTo ( null );
    frame.setVisible ( true );
}

public static class Animator extends JComponent
{
    private float angle = 0;

    public Animator ()
    {
        super ();
        setOpaque ( false );

        new Timer ( 1000 / 24, new ActionListener ()
        {
            public void actionPerformed ( ActionEvent e )
            {
                angle += 0.2f;
                if ( angle > 360 )
                {
                    angle = 0;
                }

                repaint ();
            }
        } ).start ();

        addMouseListener ( new MouseAdapter ()
        {
            //
        } );
    }

    protected void paintComponent ( Graphics g )
    {
        super.paintComponent ( g );

        Graphics2D g2d = ( Graphics2D ) g;
        g2d.setRenderingHint ( RenderingHints.KEY_ANTIALIASING,
                RenderingHints.VALUE_ANTIALIAS_ON );

        GeneralPath shape = getShape ();

        g2d.setPaint ( Color.BLACK );
        g2d.fill ( shape );
    }

    public boolean contains ( int x, int y )
    {
        return getShape ().contains ( x, y );
    }

    private GeneralPath getShape ()
    {
        GeneralPath gp = new GeneralPath ( GeneralPath.WIND_EVEN_ODD );
        gp.append ( new Rectangle2D.Double ( -250, 150, 1000, 200 ), false );

        AffineTransform at = new AffineTransform ();
        at.rotate ( angle * Math.PI / 90, 250, 250 );
        gp.transform ( at );
        return gp;
    }
}

As you can see the black rotated area not just overlays the bottom right button, but also blocks mouse events on the covered with stripe button's part. That happens due to overriden Animator's contains() method:

public boolean contains ( int x, int y )
{
    return getShape ().contains ( x, y );
}

By default component catches mouse events over the whole bounds in the parent, but by changing this method you can play with that the way you like.

Also there could be done a lot of optimizations, for eg saving the shape after each repaint to some variable and return it when checking "contains" value.

Anyway hope this helps atleast a bit in your question...