带有按键监听器的 Java swing gui 程序在 Linux 中不起作用

Question

我用java编写了一个基本的控制板GUI。当按下箭头键时，文本将显示按下键盘上的哪个按钮，并且按钮将改变颜色。

问题是这个程序在 Windows 中运行良好，但是当我在运行名为 raspbian 的 Linux 版本的树莓派上尝试它时，这似乎不起作用。当我按下按钮时，程序不执行任何操作。

package finalRobotControl;

import java.awt.Color;
import java.awt.Dimension;
import java.awt.event.KeyEvent;
import java.awt.event.KeyListener;

import javax.swing.JButton;
import javax.swing.JFrame;
import javax.swing.JLabel;
import javax.swing.JPanel;
import javax.xml.bind.Marshaller.Listener;

public class Main implements KeyListener{
    public static JButton buttonLeft;
    public static JButton buttonRight;
    public static JButton buttonUp;
    public static JButton buttonDown;
    public static JLabel stage;

    public static void main(String [] args){
        JFrame window = new JFrame("RobotController");
        window.setVisible(true);
        window.setSize(200, 200);
        window.setPreferredSize(new Dimension(400, 200));
        window.setDefaultCloseOperation(JFrame.EXIT_ON_CLOSE);

        JPanel panel = new JPanel();
        panel.setLayout(null);

        //add panel to window
        window.add(panel);

        stage = new JLabel("");
        stage.setBounds(85, 65, 50, 35);
        panel.add(stage);

        buttonLeft = new JButton("←");
        buttonLeft.setBounds(10, 65, 50, 35);
        //buttonLeft.setBackground(Color.BLUE);
        panel.add(buttonLeft);

        buttonRight = new JButton("→");
        buttonRight.setBounds(130, 65, 50, 35);
        panel.add(buttonRight);


        buttonUp = new JButton("↑");
        buttonUp.setBounds(70, 25, 50, 35);
        panel.add(buttonUp);

        buttonDown = new JButton("↓");
        buttonDown.setBounds(70, 105, 50, 35);
        panel.add(buttonDown);

        window.addKeyListener(new Main());

    }

    @Override
    public void keyPressed(KeyEvent e) {
        // TODO Auto-generated method stub
        if(e.getKeyCode() == KeyEvent.VK_LEFT){
            buttonLeft.setBackground(Color.WHITE);
            System.out.println("Left");
            stage.setText("Left");
        }
        if(e.getKeyCode() == KeyEvent.VK_RIGHT){
            buttonRight.setBackground(Color.WHITE);
            System.out.println("Right");
            stage.setText("Right");
        }
        if(e.getKeyCode() == KeyEvent.VK_UP){
            buttonUp.setBackground(Color.WHITE);
            System.out.println("Up");
            stage.setText("Up");
        }
        if(e.getKeyCode() == KeyEvent.VK_DOWN){
            buttonDown.setBackground(Color.WHITE);
            System.out.println("Down");
            stage.setText("Down");
        }
    }  

    @Override
    public void keyReleased(KeyEvent e) {
        // TODO Auto-generated method stub
        JButton lol = new JButton();
        if(e.getKeyCode() == KeyEvent.VK_LEFT){
            buttonLeft.setBackground(lol.getBackground());
            stage.setText("");
        }
        if(e.getKeyCode() == KeyEvent.VK_RIGHT){
            buttonRight.setBackground(lol.getBackground());
            stage.setText("");
        }
        if(e.getKeyCode() == KeyEvent.VK_UP){
            buttonUp.setBackground(lol.getBackground());
            stage.setText("");
        }
        if(e.getKeyCode() == KeyEvent.VK_DOWN){
            buttonDown.setBackground(lol.getBackground());
            stage.setText("");
        }




    }

    @Override
    public void keyTyped(KeyEvent arg0) {
        // TODO Auto-generated method stub

    }

}

Answer 1

KeyListener 众所周知，它对何时生成 KeyEvent 非常挑剔。仅当注册到的组件可聚焦且具有焦点时，KeyListener 才会生成 KeyEvent。

将 KeyListener 直接添加到窗口会使事情变得更加困难，因为窗口和使用之间可以存在任意数量的组件，这可能会窃取焦点。

相反，您应该使用 Key Bindings API ，它允许您控制生成关键事件所需的焦点级别