JPanel不响应KeyListener事件 [英] JPanel doesn't response to KeyListener event

问题描述

我有一个 JFrame 的子类，它使用从 JPanel扩展的类

I have a subclass of JFrame that uses a class extended from JPanel

public class HelloWorld extends JPanel implements KeyListener

我将 HelloWorld 的对象添加到框架 - app.add（helloWorld）; 。现在，当我按下任何键盘键时， KeyListener 方法被调用，似乎 helloWorld 没有窗口焦点。我也试过调用 helloWorld.requestFocusInWindow（）; 但仍然没有回复。

I add an object of HelloWorld to the frame - app.add(helloWorld);. Now, when I press any keyboard key non of the KeyListener methods gets called and it seems that helloWorld doesn't have window focus. I have tried also to invoke helloWorld.requestFocusInWindow(); but still doesn't respond.

我怎么能让它回应按键？

How can I make it respond to key press?

推荐答案

你设置了 KeyListener 你的 HelloWorld 面板会是那个面板本身？此外，您可能需要将该面板设置为可聚焦。我通过这段代码对它进行了测试，它似乎工作正常，

Did you set that KeyListener for your HelloWorld panel would be that panel itself? Also you probably need to set that panel focusable. I tested it by this code and it seems to work as it should

class HelloWorld extends JPanel implements KeyListener{
    public void keyTyped(KeyEvent e) {
        System.out.println("keyTyped: "+e);
    }
    public void keyPressed(KeyEvent e) {
        System.out.println("keyPressed: "+e);
    }
    public void keyReleased(KeyEvent e) {
        System.out.println("keyReleased: "+e);
    }
}

class MyFrame extends JFrame {
    public MyFrame() {
        setDefaultCloseOperation(EXIT_ON_CLOSE);
        setSize(200,200);

        HelloWorld helloWorld=new HelloWorld();

        helloWorld.addKeyListener(helloWorld);
        helloWorld.setFocusable(true);

        add(helloWorld);
        setVisible(true);
    }
    public static void main(String[] args) {
        new MyFrame();
    }
}

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