我试图扩展 java ScrollDemo2 以报告是否单击了画布上的形状。我从一个简单的矩形开始，相信在画布中简单地循环遍历矩形检查点击点是否包含在其中应该没有问题。但是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在 (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，如果我从 x:[0,20] y:[0,20] 单击 Jpanel，我会受到打击，而只有单击 x:[0,20] y[20,40] 才会受到打击. 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]
