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来源: 互联网 发布时间:2015-02-17
本文导语: Your mouseDragged() event handler and your paint method look like this 1. public void mouseDragged(MouseEvent e) { 2. mouseX = e.getX(); 3. mouseY = e.getY(); 4. repaint(); 5. } 6. public void paint(Graphics g) { 7. g.setColor(Color.cyan); 8. g.draw...
Your mouseDragged() event handler and your paint method look like this
1. public void mouseDragged(MouseEvent e) {
2. mouseX = e.getX();
3. mouseY = e.getY();
4. repaint();
5. }
6. public void paint(Graphics g) {
7. g.setColor(Color.cyan);
8. g.drawLine(mouseX,mouseY,mouseX+10,mouseY+10);
9. }
You want to modify your code so that the cyan lines accumulate on the screen, rather than getting erased every time repaint() calls update(). What is the simplest way to proceed?
a. On line 4, replace repaint() with paint().
b. On line 4, replace repaint() with update().
c. After line 7, add this super.update(g);
d. Add public void update(Graphics g) { paint(g); }
答案是D。
A为什么不对
|
repaint(); --〉update();---〉paint(Graphics g)
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