JPanel及其他控件中鼠标拖动画选择框

 

1. 响应鼠标按下事件，记录起始点到全局变量
2. 响应鼠标拖动事件，启用XOR模式，绘制前一个矩形（抹除前一个矩形），新建一个矩形并绘制（当前矩形）；新建矩形的算法有多种，以下采用的算法适应各个方向上的拖动；注意使用XOR模式来抹除之前绘制的矩形，千万不要使用repaint方法。
3. 响应鼠标释放时间，启用XOP模式抹除最后一次矩形

 //起始点，鼠标按下时记录Point pBegin;//绘图矩形Rectangle rect;private JPanel getJPanelWaveBox() { if (jPanelWaveBox == null) { jPanelWaveBox = new JPanel(); jPanelWaveBox.setBounds(197, 12, 543, 344); jPanelWaveBox.addMouseMotionListener(new MouseMotionAdapter() { public void mouseDragged(MouseEvent evt) {Graphics2D g2 = (Graphics2D) jPanelWaveBox.getGraphics(); //启用XOR模式g2.setXORMode(Color.white); //绘制之前的矩形if (rect != null) { g2.draw(rect);} //绘制现在的矩形rect = new Rectangle((int) Math.min(pBegin.getX(), evt.getPoint().getX()), (int) Math.min(pBegin.getY(), evt.getPoint().getY()), (int) Math.abs(pBegin.getX() - evt.getPoint().getX()),(int) Math.abs(pBegin.getY() - evt.getPoint().getY()));g2.draw(rect);g2.setPaintMode();g2.dispose();} }); jPanelWaveBox.addMouseListener(new MouseAdapter() {public void mouseReleased(MouseEvent evt) {try { // 画选择框（实际效果为去掉） Graphics2D g2 = (Graphics2D) jPanelWaveBox.getGraphics(); g2.setXORMode(Color.white); g2.draw(rect); g2.setPaintMode(); g2.dispose(); } catch (Exception e) {} pBegin = null; rect = null;}public void mousePressed(MouseEvent evt) { pBegin = evt.getPoint(); jPanelWaveBox.requestFocus(); }}); } return jPanelWaveBox;}