Question

JAVA中的KeyListener的问题！！！

有个程序，无法实现键盘的监听，高手帮忙看下是哪出错了啊！！！
程序如下：
import java.awt.Color;
import java.awt.event.ActionEvent;
import java.awt.event.ActionListener;
import java.awt.event.KeyEvent;
import java.awt.event.KeyListener;

import javax.swing.JButton;
import javax.swing.JFrame;
import javax.swing.JPanel;

public class Maze {
static private int WIDTH = 607;
static private int HEIGHT = 670;
static JButton reset;
static JButton help;
private static JPanel bb,cc;

public static void main(String[] args) {

JFrame frame = new JFrame("大虾帮帮忙");
frame.setDefaultCloseOperation(JFrame.EXIT_ON_CLOSE);
frame.setSize(WIDTH, HEIGHT);
frame.setResizable(true);
frame.setLocation(300, 100);
frame.setBackground(Color.WHITE);
Maze maze=new Maze();
bb = maze.jpanel();
cc=maze.panel();
frame.add(cc);
frame.add(bb);
frame.setVisible(true);
}

public JPanel jpanel() {
JPanel jpanel = new JPanel();
jpanel.setBackground(new Color(208, 220, 255));
reset = new JButton("重新开始");
reset.addActionListener(new ActionListener_button());
reset.setActionCommand("reset");
help = new JButton("有问题点一下");
help.addActionListener(new ActionListener_button());
help.setActionCommand("help");
jpanel.add(reset);
jpanel.add(help);
return jpanel;
}
public JPanel panel(){
JPanel panel=new JPanel();
panel.addKeyListener(new listener());
return panel;
}
class ActionListener_button implements ActionListener {
public void actionPerformed(ActionEvent e) {
if (e.getActionCommand().equals("help")) {
System.out.println("2");
} else if (e.getActionCommand().equals("reset")) {
System.out.println("3");
}
}
}

class listener implements KeyListener {

public void keyTyped(KeyEvent e) {

}
public void keyPressed(KeyEvent e) {
if (e.getKeyCode() == KeyEvent.VK_UP) {
System.out.println("6");
}
if (e.getKeyCode() == KeyEvent.VK_RIGHT) {
System.out.println("7");
}
if (e.getKeyCode() == KeyEvent.VK_DOWN) {
System.out.println("8");
}
if (e.getKeyCode() == KeyEvent.VK_LEFT) {
System.out.println("9");
}
}

public void keyReleased(KeyEvent e) {

}
}

}

Answer 1

事件监听的应该是一个实体而不是一个面板！

Answer 2

面板要实现KeyListener，必须让其setFocusable(true);

Answer 3

应该是你的两个面板，有键盘事件的那个面板给盖住了吧？都没有出现啊，修改了一下代码！如文字注释，可以运行了！！

import java.awt.Color;
import java.awt.event.ActionEvent;
import java.awt.event.ActionListener;
import java.awt.event.KeyEvent;
import java.awt.event.KeyListener;

import javax.swing.JButton;
import javax.swing.JFrame;
import javax.swing.JPanel;

public class Maze {
static private int WIDTH = 607;
static private int HEIGHT = 670;
static JButton reset;
static JButton help;
private static JPanel bb,cc;

public static void main(String[] args) {
JFrame frame = new JFrame("大虾帮帮忙");
frame.setDefaultCloseOperation(JFrame.EXIT_ON_CLOSE);
frame.setSize(WIDTH, HEIGHT);
frame.setResizable(true);
frame.setLocation(300, 100);
frame.setBackground(Color.WHITE);
//改变布局，让两上面板都能看到
frame.getContentPane().setLayout(new java.awt.GridLayout());
Maze maze=new Maze();
bb = maze.jpanel();
cc=maze.panel();
frame.add(cc);
frame.add(bb);
frame.setVisible(true);
}

public JPanel jpanel() {
JPanel jpanel = new JPanel();
jpanel.setBackground(new Color(208, 220, 255));
reset = new JButton("重新开始");
reset.addActionListener(new ActionListener_button());
reset.setActionCommand("reset");
help = new JButton("有问题点一下");
help.addActionListener(new ActionListener_button());
help.setActionCommand("help");
jpanel.add(reset);
jpanel.add(help);
return jpanel;
}
public JPanel panel(){
JPanel panel=new JPanel();
//面板上多加入一个按钮，使其可以获得键盘焦点在上面
JButton btn=new JButton("hello");
//按钮也加上键盘事件
btn.addKeyListener(new listener());
panel.add(btn);
panel.addKeyListener(new listener());
return panel;
}

class ActionListener_button implements ActionListener {
public void actionPerformed(ActionEvent e) {
if (e.getActionCommand().equals("help")) {
System.out.println("2-->help");
} else if (e.getActionCommand().equals("reset")) {
System.out.println("3-->reset");
}
}
}

class listener implements KeyListener {
public void keyTyped(KeyEvent e) {}
public void keyPressed(KeyEvent e) {
if (e.getKeyCode() == KeyEvent.VK_UP) {
System.out.println("6");
}
if (e.getKeyCode() == KeyEvent.VK_RIGHT) {
System.out.println("7");
}
if (e.getKeyCode() == KeyEvent.VK_DOWN) {
System.out.println("8");
}
if (e.getKeyCode() == KeyEvent.VK_LEFT) {
System.out.println("9");
}
}
public void keyReleased(KeyEvent e) {}
}
}