Java新手求助，关于事件监听

[lanxinglinxi]

我在看韩顺平的教程时，自己尝试写的坦克移动小程序一直不能动，希望各位大神轻拍，指出哪里出问题了，我实在是没找到。。。

import java.awt.*;
import java.awt.event.*;
import javax.swing.*;

public class demo {
	JFrame frame;
	MyPanel panel;

	public demo() {
		frame = new JFrame();
		panel = new MyPanel();
		panel.addKeyListener(panel);// 添加监听
		frame.add(panel);
		frame.setTitle("坦克");
		frame.setSize(500, 500);
		frame.setResizable(false);
		frame.setDefaultCloseOperation(JFrame.EXIT_ON_CLOSE);
		frame.setVisible(true);
	}

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

class Tank {
	int x;
	int y;
	int direction;// 方向：0-上,1-右,2-下,3-左
	int interval;// 步长

	public int getX() {
		return x;
	}

	public void setX(int x) {
		this.x = x;
	}

	public int getY() {
		return y;
	}

	public void setY(int y) {
		this.y = y;
	}

	public int getDirection() {
		return direction;
	}

	public void setDirection(int direction) {
		this.direction = direction;
	}

	public int getInterval() {
		return interval;
	}

	public void setInterval(int interval) {
		this.interval = interval;
	}

	public Tank(int x, int y, int direction, int interval) {
		this.x = x;
		this.y = y;
		this.direction = direction;
		this.interval = interval;
	}

	public void MoveUp() {
		y -= interval;
	}

	public void MoveDown() {
		y += interval;
	}

	public void MoveLeft() {
		x -= interval;
	}

	public void MoveRight() {
		x += interval;
	}
}

class Enemy extends Tank {
	public Enemy(int x, int y, int direction, int interval) {
		super(x, y, direction, interval);
	}
}

class Ally extends Tank {
	public Ally(int x, int y, int direction, int interval) {
		super(x, y, direction, interval);
	}
}

class MyPanel extends JPanel implements KeyListener {
	int x;
	int y;
	int direction;
	int interval;
	Ally a1;

	public MyPanel() {
		x = 100;
		y = 100;
		direction = 0;
		interval = 10;
		a1 = new Ally(x, y, direction, interval);
	}

	public void paint(Graphics gra) {// 第一次显示的时候会被自动调用，窗口最小最大
		super.paint(gra);
		drawTank(a1.getX(), a1.getY(), a1.getDirection(), gra);
	}

	public void drawTank(int x, int y, int direction, Graphics gra) {
		switch (direction) {
		case 0: {
			gra.draw3DRect(x, y, 5, 30, false);
			gra.draw3DRect(x + 15, y, 5, 30, false);
			gra.draw3DRect(x + 5, y + 5, 10, 20, false);
			gra.fillOval(x + 5, y + 10, 10, 10);
			gra.drawLine(x + 10, y, x + 10, y + 15);
			break;
		}
		case 1: {
			gra.draw3DRect(x, y, 30, 5, false);
			gra.draw3DRect(x, y + 15, 30, 5, false);
			gra.draw3DRect(x + 5, y + 5, 20, 10, false);
			gra.fillOval(x + 10, y + 5, 10, 10);
			gra.drawLine(x+15, y + 10, x + 30, y + 10);
			break;
		}
		case 2: {
			gra.draw3DRect(x, y, 5, 30, false);
			gra.draw3DRect(x + 15, y, 5, 30, false);
			gra.draw3DRect(x + 5, y + 5, 10, 20, false);
			gra.fillOval(x + 5, y + 10, 10, 10);
			gra.drawLine(x + 10, y + 30, x + 10, y + 15);
			break;
		}
		case 3: {
			gra.draw3DRect(x, y, 30, 5, false);
			gra.draw3DRect(x, y + 15, 30, 5, false);
			gra.draw3DRect(x + 5, y + 5, 20, 10, false);
			gra.fillOval(x + 10, y + 5, 10, 10);
			gra.drawLine(x, y + 10, x + 15, y + 10);
			break;
		}
		default:
			break;
		}
	}

	public void keyPressed(KeyEvent e) {
		System.out.println("(" + a1.getX() + "," + a1.getY() + ")");
		if (e.getKeyCode() == KeyEvent.VK_UP) {
			a1.setDirection(0);
			a1.MoveUp();
		} else if (e.getKeyCode() == KeyEvent.VK_DOWN) {
			a1.setDirection(2);
			a1.MoveDown();
		} else if (e.getKeyCode() == KeyEvent.VK_LEFT) {
			a1.setDirection(3);
			a1.MoveLeft();
		} else if (e.getKeyCode() == KeyEvent.VK_RIGHT) {
			a1.setDirection(1);
			a1.MoveRight();
		}
		repaint();
	}

	public void keyReleased(KeyEvent e) {
	}

	public void keyTyped(KeyEvent e) {
	}

}

[lanxinglinxi]

自己找到的答案 http://stackoverflow.com/questions/11487369/jpanel-doesnt-response-to-keylistener-event JPanel is not Focusable by default. That is, it can not respond to focus related events, meaning that it can not respond to the keyevents. I would suggest trying to setFocusable on the pane to true and trying again. Make sure you click the panel first to make sure it receives focus.

[MarkTuna]

KeyEvent.VK_DOWN 这个是数字键盘的上下左右键哦，换成 VK_DOWN 试试看

[lanxinglinxi]

引用 2 楼 tuyugg123 的回复:

KeyEvent.VK_DOWN 这个是数字键盘的上下左右键哦，换成 VK_DOWN 试试看

看我一楼的回复

[三仙半]

在demo的构造函数中启动一个线程，不断的调用panel的requestFocusInWindow()方法，直到panel的isFocusOwner()方法的返回值为true，这样，就不用先点击依次这个panel了，另外，给panel注册个焦点事件监听，一旦失去焦点，立刻调用panel的requestFocusInWindow()方法申请获得焦点。