Java HitTest 行为异常

Question

我试图扩展 java ScrollDemo2 来报告 Canvas 上的形状是否被单击。我从一个简单的矩形开始，相信简单地循环 Canvas 中的矩形检查点击点是否包含在其中应该没有问题。但随后发生了一些奇怪的事情， contains 方法似乎只关心该点是否位于锚定于 (0,0) 的矩形中，并且似乎并不关心我的组件位于 y=20 处。因此，如果我在 x:[0,20] y:[0,20] 中单击 Jpanel，我就会受到打击，而只有在单击 x:[0,20] y[20,40] 时才应该受到打击。 。这是一个错误，还是我做错了什么？

public class CachedDrawableComponent extends JComponent
{
//this will do more later
    CachedDrawableComponent(Rectangle bounds)
    {
        this.setBounds(bounds);
    }
    protected void paintComponent(Graphics g)
    {
        g.setColor(Color.magenta);
        Rectangle r = this.getBounds();
        g.fillRect(r.x, r.y, r.width, r.height);
    }

}

public class ScrollDemo2 extends JPanel
                         implements MouseListener {
    private Dimension area; //indicates area taken up by graphics
    private Vector<Rectangle> circles; //coordinates used to draw graphics
    private Vector<CachedDrawableComponent> otherDrawables;
    private JPanel drawingPane;

    private final Color colors[] = {
        Color.red, Color.blue, Color.green, Color.orange,
        Color.cyan, Color.magenta, Color.darkGray, Color.yellow};
    private final int color_n = colors.length;

    public ScrollDemo2() {
        super(new BorderLayout());

        area = new Dimension(0,0);
        circles = new Vector<Rectangle>();
        this.otherDrawables = new Vector<CachedDrawableComponent>();

        //Set up the instructions.
        JLabel instructionsLeft = new JLabel(
                        "Click left mouse button to place a circle.");
        JLabel instructionsRight = new JLabel(
                        "Click right mouse button to clear drawing area.");
        JPanel instructionPanel = new JPanel(new GridLayout(0,1));
        instructionPanel.setFocusable(true);
        instructionPanel.add(instructionsLeft);
        instructionPanel.add(instructionsRight);

        //Set up the drawing area.
        drawingPane = new DrawingPane();
        drawingPane.setBackground(Color.white);
        drawingPane.addMouseListener(this);
        TestRect t = new TestRect(new Rectangle(0,20,20,20));
        this.otherDrawables.add(t); 


        //Put the drawing area in a scroll pane.
        JScrollPane scroller = new JScrollPane(drawingPane);
        scroller.setPreferredSize(new Dimension(200,200));

        //Lay out this demo.
        add(instructionPanel, BorderLayout.PAGE_START);
        add(scroller, BorderLayout.CENTER);
    }

    /** The component inside the scroll pane. */
    public class DrawingPane extends JPanel {
        protected void paintComponent(Graphics g) {
            super.paintComponent(g);

            Rectangle rect;
            for (int i = 0; i < circles.size(); i++) {
                rect = circles.elementAt(i);
                g.setColor(colors[(i % color_n)]);
                g.fillOval(rect.x, rect.y, rect.width, rect.height);

            }

            for (int i = 0; i < otherDrawables.size(); i++) {
                CachedDrawableComponent drawMe = otherDrawables.elementAt(i);;
                g.setColor(colors[(i % color_n)]);
                drawMe.paint(g);

            }
        }
    }

    //Handle mouse events.
    public void mouseReleased(MouseEvent e) {
        final int W = 100;
        final int H = 100;
        boolean changed = false;
        if (SwingUtilities.isRightMouseButton(e)) {
            //This will clear the graphic objects.
            circles.removeAllElements();
            area.width=0;
            area.height=0;
            changed = true;
        } else {
            int x = e.getX() - W/2;
            int y = e.getY() - H/2;
            if (x < 0) x = 0;
            if (y < 0) y = 0;
            Rectangle rect = new Rectangle(x, y, W, H);
            circles.addElement(rect);
            drawingPane.scrollRectToVisible(rect);

            int this_width = (x + W + 2);
            if (this_width > area.width) {
                area.width = this_width; changed=true;
            }

            int this_height = (y + H + 2);
            if (this_height > area.height) {
                area.height = this_height; changed=true;
            }
        }
        if (changed) {
            //Update client's preferred size because
            //the area taken up by the graphics has
            //gotten larger or smaller (if cleared).
            drawingPane.setPreferredSize(area);

            //Let the scroll pane know to update itself
            //and its scrollbars.
            drawingPane.revalidate();
        }
        drawingPane.repaint();
    }
    public void mouseClicked(MouseEvent e){}
    public void mouseEntered(MouseEvent e){}
    public void mouseExited(MouseEvent e){}
    public void mousePressed(MouseEvent e)
    {
        System.out.println("Did press:"+e.getPoint());
        System.out.println(otherDrawables.get(0).getBounds());
        if(otherDrawables.get(0).contains(e.getPoint()))
        {
            System.out.println("Did Hit");
        }

    }

    /**
     * Create the GUI and show it.  For thread safety,
     * this method should be invoked from the
     * event-dispatching thread.
     */
    private static void createAndShowGUI() {
        //Create and set up the window.
        JFrame frame = new JFrame("ScrollDemo2");
        frame.setDefaultCloseOperation(JFrame.EXIT_ON_CLOSE);

        //Create and set up the content pane.
        JComponent newContentPane = new ScrollDemo2();
        newContentPane.setOpaque(true); //content panes must be opaque
        frame.setContentPane(newContentPane);

        //Display the window.
        frame.pack();
        frame.setVisible(true);
    }

    public static void main(String[] args) {
        //Schedule a job for the event-dispatching thread:
        //creating and showing this application's GUI.
        javax.swing.SwingUtilities.invokeLater(new Runnable() {
            public void run() {
                createAndShowGUI();
            }
        });
    }
}



Output:

    Did press:java.awt.Point[x=8,y=7]
    java.awt.Rectangle[x=0,y=20,width=20,height=20]
    Did Hit
    Did press:java.awt.Point[x=14,y=89]
    java.awt.Rectangle[x=0,y=20,width=20,height=20]

Answer 1

面临的问题是您正在混合坐标系:

• mouseListener中的坐标是drawingPane的坐标
• somecomponent.contains 中预期的坐标是组件的坐标

来自 contains 的 api 文档:

Checks whether this component "contains" the specified point, where x and y are defined to be relative to the coordinate system of this component.

拥有这些组件而不将它们实际添加到绘图 Pane 中是不寻常的(没有充分的理由就不要这样做:-)。