如何在 JLabel 上使用键绑定？ [复制]

Question

我是使用 java 编码的初学者（也使用英语），我正在尝试使用 eclipse 制作乒乓球游戏。 我的问题是我不知道如何通过按键盘上的不同键来移动我的 2 个球拍（JLabel）。 我第一次尝试使用 KeyListener 但我没有成功，所以现在我尝试使用 keyBinding，我阅读了很多教程但我不太了解。

那么我怎样才能通过按箭头键简单地让我的两个球拍移动。

这里是部分代码：

import java.awt.Color;
import javax.swing.*;
import java.awt.event.*;

public class Pongg extends JPanel implements KeyListener {


private JLabel Racket1;                   // <----- Déclaration des JLabel/JLayeredPane ici pour pouvoir les utiliser (KeyListener)
private JLabel Racket2;                   //


public Pongg() {


    //Création de la fenetre
    JFrame fenetre = new JFrame("Fenetre");
    fenetre.setLocationRelativeTo (null);
    fenetre.setVisible(true);
    fenetre.setDefaultCloseOperation(JFrame.EXIT_ON_CLOSE);
    fenetre.setSize(1000,600);

    //Box Main + JLayeredPane (fond noir)
    Box main=Box.createVerticalBox();
    JLayeredPane Fond = new JLayeredPane();
    Fond.setBackground(Color.black);        
    Fond.setOpaque(true);
    Fond.setVisible(true);

    main.add(Fond);
    fenetre.add(main);

    //Plateformes
    JLabel Racket1 = new JLabel();
    JLabel Racket2 = new JLabel();      

    //--->Racket 1 :        
    Racket1.setBounds(50, 200, 16, 100);   //<----- setBounds (Placer position du JLabel x,y + taille de la plateforme x,y)
    Racket1.setBackground(Color.white);
    Racket1.setOpaque(true);



    //--->Racket 2 :

    Racket2.setBounds(900, 200, 16, 100);
    Racket2.setBackground(Color.white);
    Racket2.setOpaque(true);

    Fond.add(Racket1); 
    Fond.add(Racket2);

EDDIT：这里我尝试用 keyListener 来做（我不知道如何用 keyBinding 来做）：

private Set appuye = new HashSet();

    public void keyTyped(KeyEvent e) {
    }

    public void keyPressed(KeyEvent e) {
        appuye.add(e.getKeyCode()); // On ajoute le nombre correspondant à la touche pressée à la liste
            if (appuye.contains(KeyEvent.VK_UP)) { // la liste contient-elle cette touche ? (c'est un int static, donc utilisable à partir de la classe, même sans objet)
                Racket1.setLocation(Racket1.getX(), Racket1.getY() - 16);
            }
            if (appuye.contains(KeyEvent.VK_DOWN)) {
                Racket1.setLocation(Racket1.getX(), Racket1.getY() + 16);
            }
            if (appuye.contains(KeyEvent.VK_A)) {
                Racket2.setLocation(Racket2.getX(), Racket2.getY() - 16);
            }
            if (appuye.contains(KeyEvent.VK_Q)) {
                Racket2.setLocation(Racket2.getX(), Racket2.getY() + 16);
            }
    }

    public void keyReleased(KeyEvent e) {
        appuye.remove(e.getKeyCode()); // Lorsque la touche est relachée, on retire son numéro de la liste.

}           

Answer 1

键绑定和KeyListener是有区别的，一般来说，键绑定是首选。

请参阅How to write a KeyListener 和How to use key bindings 了解更多详情

要使用键绑定 API，您首先需要的是某种 Action 来响应键绑定。既然你只想让两个JLabels 上下移动，这其实很简单...

public class MoveAction extends AbstractAction {

    private JLabel label;
    private int yDelta;

    public MoveAction(JLabel label, int yDelta) {
        this.label = label;
        this.yDelta = yDelta;
    }

    @Override
    public void actionPerformed(ActionEvent e) {
        System.out.println("...");
        Point p = label.getLocation();
        p.y += yDelta;
        label.setLocation(p);

        label.getParent().repaint();
    }

}

接下来您需要做的是使用Action 注册击键（将它们绑定在一起）

InputMap im = Racket1.getInputMap(WHEN_IN_FOCUSED_WINDOW);
ActionMap am = Racket1.getActionMap();

im.put(KeyStroke.getKeyStroke(KeyEvent.VK_W, 0), "Left.down.up");
im.put(KeyStroke.getKeyStroke(KeyEvent.VK_S, 0), "Left.down.down");
am.put("Left.down.up", new MoveAction(Racket1, -4));
am.put("Left.down.down", new MoveAction(Racket1, 4));

例如...

import java.awt.BorderLayout;
import java.awt.Color;
import java.awt.Dimension;
import java.awt.EventQueue;
import java.awt.Point;
import java.awt.event.ActionEvent;
import java.awt.event.KeyEvent;
import javax.swing.AbstractAction;
import javax.swing.ActionMap;
import javax.swing.InputMap;
import javax.swing.JFrame;
import javax.swing.JLabel;
import javax.swing.JLayeredPane;
import javax.swing.JPanel;
import javax.swing.KeyStroke;
import javax.swing.UIManager;
import javax.swing.UnsupportedLookAndFeelException;

public class Pongg extends JPanel {

    private JLabel Racket1;                                  // <----- Déclaration des JLabel/JLayeredPane ici pour pouvoir les utiliser (KeyListener)
    private JLabel Racket2;                                  //

    public static void main(String[] args) {
        EventQueue.invokeLater(new Runnable() {
        @Override
        public void run() {
            try {
            UIManager.setLookAndFeel(UIManager.getSystemLookAndFeelClassName());
            } catch (ClassNotFoundException | InstantiationException | IllegalAccessException | UnsupportedLookAndFeelException ex) {
            ex.printStackTrace();
            }

            JFrame frame = new JFrame("Testing");
            frame.setDefaultCloseOperation(JFrame.EXIT_ON_CLOSE);
            frame.add(new Pongg());
            frame.pack();
            frame.setLocationRelativeTo(null);
            frame.setVisible(true);
        }
        });
    }

    public Pongg() {

        setLayout(new BorderLayout());

        //Box Main + JLayeredPane (fond noir)
        JLayeredPane Fond = new JLayeredPane();
        Fond.setBackground(Color.black);
        Fond.setOpaque(true);
        Fond.setVisible(true);

        add(Fond);

        //Plateformes
        JLabel Racket1 = new JLabel();
        JLabel Racket2 = new JLabel();

        //--->Racket 1 :                
        Racket1.setBounds(50, 200, 16, 100);     //<----- setBounds (Placer position du JLabel x,y + taille de la plateforme x,y)
        Racket1.setBackground(Color.white);
        Racket1.setOpaque(true);

        //--->Racket 2 :
        Racket2.setBounds(900, 200, 16, 100);
        Racket2.setBackground(Color.white);
        Racket2.setOpaque(true);

        Fond.add(Racket1);
        Fond.add(Racket2);

        InputMap im = Racket1.getInputMap(WHEN_IN_FOCUSED_WINDOW);
        ActionMap am = Racket1.getActionMap();

        im.put(KeyStroke.getKeyStroke(KeyEvent.VK_W, 0), "Left.down.up");
        am.put("Left.down.up", new MoveAction(Racket1, -4));
    }

    @Override
    public Dimension getPreferredSize() {

        return new Dimension(1000, 600);

    }



    public class MoveAction extends AbstractAction {

        private JLabel label;
        private int yDelta;

        public MoveAction(JLabel label, int yDelta) {
            this.label = label;
            this.yDelta = yDelta;
        }

        @Override
        public void actionPerformed(ActionEvent e) {
            System.out.println("...");
            Point p = label.getLocation();
            p.y += yDelta;
            label.setLocation(p);

            label.getParent().repaint();
        }

    }
}