java - Java is not picking up keypresses?

Question

I have a program which produces a JFrame and then a JPanel on top of it. For the program, I have tried implementing the KeyListener and then adding the methods (for both components), but the program does not pick any of my key strokes up. What am I doing wrong?

EDIT

This is my code. It is a part of the class which creates the JFrame. It still does not pick up the press of the ESC key.

@Override
public void keyTyped(KeyEvent e) {

}

@Override
public void keyPressed(KeyEvent e) {
    int keyCode = e.getKeyCode();

    if(keyCode == KeyEvent.VK_ESCAPE){
        System.out.println("Hi");

    }else{
        System.out.println("Hello");

    }

}

@Override
public void keyReleased(KeyEvent e) {

}

Answer 1

如果没有您的代码，我只能告诉您，通常当人们问这个问题时，他们不知道该接口KeyListener包含三个方法，正如 Agusti-N 在此处的回答中所说：

void keyTyped(KeyEvent)
void keyPressed(KeyEvent)
void keyReleased(KeyEvent)

如果您使用keyTyped并且正在使用event.getKeyCode()来检查输入的字符，这将不起作用。你应该使用getKeyChar()forkeyTyped和getKeyCode()forkeyPressed和keyReleased。否则你会得到null. 只有在没有其他选择的情况下才应该使用它，在大多数情况下，您想使用Key Bindings。