为什么捕捉不到键盘事件，很郁闷！！

Question

源码如下：
/*** Tetra2.java ***/
package Tetra;import javax.swing.*;
import java.awt.*;
import java.awt.event.*;public class Tetra2 extends JFrame{

JButton jb = new JButton();

public Tetra2(){ setFocusable(true);
addKeyListener(new KeyAdapter(){
public void keyReleased(){
System.out.println("keyevent");
}

public void keyPressed(){
System.out.println("keyevent");
}

public void keyTyped(){
System.out.println("keyevent");
}

}
);
}

public static void main(String args[]){
Tetra2 t = new Tetra2();
t.show();
}
}焦点的问题我也注意到了呀，随便按什么键都不会print出keyevent。急！
谢谢指教！！！

Answer 1

监听的部分怎么写到constructor里去了。改成这样吧
/*** Tetra2.java ***/
package Tetra2;import javax.swing.*;
import java.awt.event.*;public class Tetra2 extends JFrame {

JButton jb = new JButton();

public Tetra2(){ setFocusable(true);
/*addKeyListener(new KeyAdapter(){
public void keyReleased(){
System.out.println("keyevent");
}

public void keyPressed(){
System.out.println("keyevent");
}

public void keyTyped(){
System.out.println("keyevent");
}

}
);*/
}

public static void main(String args[]){
Tetra2 t = new Tetra2();
t.addKeyListener(new KeyListener() { public void keyTyped(KeyEvent e) {
// TODO Auto-generated method stub
System.out.println("keyevent");
} public void keyPressed(KeyEvent e) {
// TODO Auto-generated method stub
System.out.println("keyevent");
} public void keyReleased(KeyEvent e) {
// TODO Auto-generated method stub
System.out.println("keyevent");
}

});
t.show();
}
}

Answer 2

好像还可以通过实现KeyEventPostProcessor接口来实现，事先用KeyboardFocusManager注删一下，再实现public boolean postProcessKeyEvent(KeyEvent e){}方法.

Answer 3

JButton jb = new JButton()是多余的楼主参考下
import javax.swing.*;
import java.awt.*;
import java.awt.event.*;public class Tetra2
{
public static void main(String args[])
{
Tetra2JFrame t = new Tetra2JFrame();
t.show();
}
}
class Tetra2JFrame extends JFrame
{
public Tetra2JFrame()
{
setFocusable(true);
addKeyListener(new KeyAdapter()
{
public void keyPressed(KeyEvent event)
{
System.out.println("keyevent");
} });
}
}

Answer 4

楼主代码KeyAdapter的三个方法都丢掉了参数KeyEvent event
应该是
public void keyReleased(KeyEvent event){
System.out.println("keyevent");
}

public void keyPressed(KeyEvent event){
System.out.println("keyevent");
}

public void keyTyped(KeyEvent event){
System.out.println("keyevent");
}

Answer 5

为什么不用ide自动加入代码，你这样手写小程序还行，一旦组件多了，就顾头不顾脚了

Answer 6

addKeyListener(new KeyAdapter(){
public void keyReleased(){ //少了KeyEvent参数吧
System.out.println("keyevent");
}

public void keyPressed(){//少了KeyEvent参数吧
System.out.println("keyevent");
}

public void keyTyped(){//少了KeyEvent参数吧
System.out.println("keyevent");
}

}