Question

Java事件处理机制里的actionevevt和keyevent有什么区别和联系？

Answer 1

你没有把KeyListener监听加到JFrame中，在MovingBall类中的this.add(mp); 语句后面加上一句this.addKeyListener(mp);就行了。完整的程序如下：
import java.awt.*;
import java.awt.event.KeyEvent;
import java.awt.event.KeyListener;
import javax.swing.*;

public class MovingBall extends JFrame{

MyPanel mp=null;

public MovingBall(){
mp= new MyPanel();

this.add(mp);
this.addKeyListener(mp); //这里加了一句
this.setSize(400,300);
this.setTitle("Moving Ball");
this.setLocationRelativeTo(null);
this.setVisible(true);
}

public static void main(String[] args) {
MovingBall movingBall= new MovingBall();
}
}

class MyPanel extends JPanel implements KeyListener{
int x=10;
int y=10;

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

public void keyPressed(KeyEvent e) {
if(e.getKeyCode()==KeyEvent.VK_DOWN){
y++;
}
else if(e.getKeyCode()==KeyEvent.VK_UP){
y--;
}
else if(e.getKeyCode()==KeyEvent.VK_LEFT){
x--;
}
else if(e.getKeyCode()==KeyEvent.VK_RIGHT){
x++;
}
this.repaint();
}

public void keyReleased(KeyEvent arg0) {
// TODO Auto-generated method stub

}

public void keyTyped(KeyEvent arg0) {
// TODO Auto-generated method stub

}

}

Answer 2

你可以点就去看看他们的源码