为什么添加了按钮后，JFrame的按键监听不起作用了？

[blackkettle]

Java 达人，

我写了一个 java 程序，一个面板上有两个按钮，同时监听用户的按键操作。

不添加按钮，按键操作的监听正常；添加按钮后，按键操作的监听就失效了。

请达人指点迷津。十分感谢！

代码如下：

import java.awt.BorderLayout;
import java.awt.FlowLayout;
import java.awt.event.KeyEvent;
import java.awt.event.KeyListener;
import java.awt.event.MouseEvent;
import java.awt.event.MouseListener;
import java.text.SimpleDateFormat;
import java.util.Date;

import javax.swing.*; 
import javax.swing.table.DefaultTableModel;
import javax.swing.table.TableModel;

public class Demo20 extends JFrame implements KeyListener{
	
	private static final long serialVersionUID = 1L;

	public Demo20(){
		this.setTitle("键盘事件处理");
		this.setSize(300, 200);
		this.setLocationRelativeTo(this);// 窗口居中
		this.setVisible(true);
		this.setDefaultCloseOperation(JFrame.EXIT_ON_CLOSE);// 窗口关闭动作处理
		this.addKeyListener(this);// 添加注册键盘事件监听器
		this.setLayout(new FlowLayout(FlowLayout.LEFT,45,45));
		
		JButton buttonPop = new JButton("Pop out");
		this.add(buttonPop);
		
		buttonPop.addMouseListener(new MouseListener(){
			public void mouseClicked(MouseEvent e) {
				System.out.println("Pop up!");
			}

			public void mousePressed(MouseEvent e) {
			}

			public void mouseReleased(MouseEvent e) {
			}

			public void mouseEntered(MouseEvent e) {
			}

			public void mouseExited(MouseEvent e) {
			}
		});
		
		JButton buttonPrint = new JButton("Print");
		this.add(buttonPrint);
		
		buttonPrint.addMouseListener(new MouseListener(){
			public void mouseClicked(MouseEvent e) {
				System.out.println("Print!");
			}

			public void mousePressed(MouseEvent e) {
			}

			public void mouseReleased(MouseEvent e) {
			}

			public void mouseEntered(MouseEvent e) {
			}

			public void mouseExited(MouseEvent e) {
			}
		});
	}		

	@Override
	public void keyPressed(KeyEvent arg0){// 敲击
	}

	@Override
	public void keyReleased(KeyEvent arg0) {// 按下
		if (arg0.getKeyCode() == 114) {// 114 F3对应的编码			
			Demo10.print();
		}
		
		if (arg0.getKeyCode() == 80) {// 80 P 对应的编码			
			System.out.println("Key P is pressed!");
		}
	}

	@Override
	public void keyTyped(KeyEvent arg0) {// 释放
	}

	public static void main(String[] args) {
		new Demo20();
	}

	public static void print() {
		System.out.println("Running!");
	}
}

[书断华]

当添加按钮以后 JFrame 就会丢失焦点所以我们要从新获取焦点。

import java.awt.BorderLayout;
import java.awt.FlowLayout;
import java.awt.event.KeyEvent;
import java.awt.event.KeyListener;
import java.awt.event.MouseEvent;
import java.awt.event.MouseListener;
import java.text.SimpleDateFormat;
import java.util.Date;

import javax.swing.*; 
import javax.swing.table.DefaultTableModel;
import javax.swing.table.TableModel;

public class Demo20 extends JFrame implements KeyListener{
    
    private static final long serialVersionUID = 1L;

    public Demo20(){
        this.setTitle("键盘事件处理");
        this.setSize(300, 200);
        this.setLocationRelativeTo(this);// 窗口居中
        this.setVisible(true);
        this.setDefaultCloseOperation(JFrame.EXIT_ON_CLOSE);// 窗口关闭动作处理
        this.addKeyListener(this);// 添加注册键盘事件监听器
        this.setLayout(new FlowLayout(FlowLayout.LEFT,45,45));
        
        JButton buttonPop = new JButton("Pop out");
        this.add(buttonPop);
        
        buttonPop.addMouseListener(new MouseListener(){
            public void mouseClicked(MouseEvent e) {
                System.out.println("Pop up!");
                Demo20.this.requestFocus();
            }

            public void mousePressed(MouseEvent e) {
            }

            public void mouseReleased(MouseEvent e) {
            }

            public void mouseEntered(MouseEvent e) {
            }

            public void mouseExited(MouseEvent e) {
            }
        });
        
        JButton buttonPrint = new JButton("Print");
        this.add(buttonPrint);
        
        buttonPrint.addMouseListener(new MouseListener(){
            public void mouseClicked(MouseEvent e) {
                System.out.println("Print!");
                Demo20.this.requestFocus();
            }

            public void mousePressed(MouseEvent e) {
            }

            public void mouseReleased(MouseEvent e) {
            }

            public void mouseEntered(MouseEvent e) {
            }

            public void mouseExited(MouseEvent e) {
            }
        });
        this.requestFocus();
    }        

    @Override
    public void keyPressed(KeyEvent arg0){// 敲击
    }

    @Override
    public void keyReleased(KeyEvent arg0) {// 按下
        if (arg0.getKeyCode() == 114) {// 114 F3对应的编码            
//            Demo10.print();
        }
        
        if (arg0.getKeyCode() == 80) {// 80 P 对应的编码            
            System.out.println("Key P is pressed!");
        }
    }

    @Override
    public void keyTyped(KeyEvent arg0) {// 释放
    }

    public static void main(String[] args) {
        new Demo20();
    }

    public static void print() {
        System.out.println("Running!");
    }
}

[书断华]

加上注释

import java.awt.BorderLayout;
import java.awt.FlowLayout;
import java.awt.event.KeyEvent;
import java.awt.event.KeyListener;
import java.awt.event.MouseEvent;
import java.awt.event.MouseListener;
import java.text.SimpleDateFormat;
import java.util.Date;

import javax.swing.*; 
import javax.swing.table.DefaultTableModel;
import javax.swing.table.TableModel;

public class Demo20 extends JFrame implements KeyListener{
    
    private static final long serialVersionUID = 1L;

    public Demo20(){
        this.setTitle("键盘事件处理");
        this.setSize(300, 200);
        this.setLocationRelativeTo(this);// 窗口居中
        this.setVisible(true);
        this.setDefaultCloseOperation(JFrame.EXIT_ON_CLOSE);// 窗口关闭动作处理
        this.addKeyListener(this);// 添加注册键盘事件监听器
        this.setLayout(new FlowLayout(FlowLayout.LEFT,45,45));
        
        JButton buttonPop = new JButton("Pop out");
        this.add(buttonPop);
        
        buttonPop.addMouseListener(new MouseListener(){
            public void mouseClicked(MouseEvent e) {
                System.out.println("Pop up!");
                Demo20.this.requestFocus();//点击按钮后获取焦点
            }

            public void mousePressed(MouseEvent e) {
            }

            public void mouseReleased(MouseEvent e) {
            }

            public void mouseEntered(MouseEvent e) {
            }

            public void mouseExited(MouseEvent e) {
            }
        });
        
        JButton buttonPrint = new JButton("Print");
        this.add(buttonPrint);
        
        buttonPrint.addMouseListener(new MouseListener(){
            public void mouseClicked(MouseEvent e) {
                System.out.println("Print!");
                Demo20.this.requestFocus();//点击按钮后获取焦点
            }

            public void mousePressed(MouseEvent e) {
            }

            public void mouseReleased(MouseEvent e) {
            }

            public void mouseEntered(MouseEvent e) {
            }

            public void mouseExited(MouseEvent e) {
            }
        });
        this.requestFocus();//创建完后先获取焦点。
    }        

    @Override
    public void keyPressed(KeyEvent arg0){// 敲击
    }

    @Override
    public void keyReleased(KeyEvent arg0) {// 按下
        if (arg0.getKeyCode() == 114) {// 114 F3对应的编码            
//            Demo10.print();
        }
        
        if (arg0.getKeyCode() == 80) {// 80 P 对应的编码            
            System.out.println("Key P is pressed!");
        }
    }

    @Override
    public void keyTyped(KeyEvent arg0) {// 释放
    }

    public static void main(String[] args) {
        new Demo20();
    }

    public static void print() {
        System.out.println("Running!");
    }
}

[孤雨]

重新获取焦点

[blackkettle]

zhang5059,

你太强了。

多谢！

[scbb]

楼主不知道标准是这么做的。
但我下面这样可以用。

把按钮的key事件传给他parent也就是你的JFrame。
（我只写了1个按钮的，另一个按钮同样。）

        buttonPop.addKeyListener(new KeyListener() {
			@Override
			public void keyPressed(KeyEvent arg0) {
				Demo20.this.keyPressed(arg0);				
			}
			@Override
			public void keyReleased(KeyEvent arg0) {
				Demo20.this.keyReleased(arg0);				
			}
			@Override
			public void keyTyped(KeyEvent arg0) {
				Demo20.this.keyTyped(arg0);				
			}        	
        });

[scbb]

[Quote=引用 4 楼 的回复:]

zhang5059,

你太强了。

多谢！
[/Quote]

zhang5059的做法，你按tab键把焦点移到按钮上，key事件又会没得。

[blackkettle]

scbb,

好厉害！！！

我再改一下。

非常感谢！