e.txt

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/** 
*可以用鼠标和键盘控制小球的移动 
*练习鼠标和键盘的事件处理 
**/ 
import java.awt.* ; 
import java.awt.event.* ; 

public class MyDraggedBall { 
public static void main(String args[]){ 
Frame w = new Frame() ; 
w.setSize(300 , 400) ; 

MyPanel mp = new MyPanel() ; 
w.add(mp) ; 

w.addMouseMotionListener(mp) ; 
mp.addMouseMotionListener(mp) ; 

w.addKeyListener(mp) ; 
mp.addKeyListener(mp) ; 

w.show() ; 
} 
} 

class MyPanel extends Panel implements MouseMotionListener, KeyListener{ 

int x = 30 ; 
int y = 30 ; 

public void paint(Graphics g) { 
g.fillOval(x , y , 10 , 10) ; 
} 

public void mouseDragged(MouseEvent e) { 

if(x >= 0 && x <= 282 && y >= 0 && y <= 356) { 
x = e.getX() ; 
y = e.getY() ; 
}else{//out of border 

if(x < 0) { 
x = 0 ; 
} 
if(x > 282) { 
x = 282 ; 
} 
if(y > 356){ 
y = 356 ; 
} 
if(y < 0) { 
y = 0 ; 
} 

} 

repaint() ; 
} 

public void mouseMoved(MouseEvent e) { 

} 

public void keyTyped(KeyEvent e) { 

} 

public void keyPressed(KeyEvent e) { 

if(e.getKeyCode() == 37) { 
if(x > 0) { 
x -- ; 
} 
} 

if(e.getKeyCode() == 38) { 
if(y > 0) { 
y -- ; 
} 
} 

if(e.getKeyCode() == 39) { 
if(x < 282) { 
x ++ ; 
} 
} 

if(e.getKeyCode() == 40) { 
if(y < 356) { 
y ++ ; 
} 
} 

repaint() ; 
} 

public void keyReleased(KeyEvent e) { 

} 

}