java - 用于多个箭头键按下的 KeyBinding

Question

这段代码适合多次按下箭头键吗？现在正在工作。向右走，向左走。但是，如果我同时按下向左和向右箭头键，我希望该桨停止。我怎样才能做到这一点 ？

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

public class GamePanel extends JPanel {

// ENUM     
public enum HorizontalMovement {
    NONE,
    LEFT,
    RIGHT
}

// CONSTANTS    
private static final int WIDTH = 600;
private static final int HEIGHT = 500;
private static final int PADDLE_Y = 475;
private static final int PADDLE_W = 80;
private static final int PADDLE_H = 20;
private static final int PADDLE_ARC = 15;       

// PROPERTIES   
int x = 0;  
private HorizontalMovement horizontalMovement = HorizontalMovement.NONE;
private Timer timer;

// CONSTRUCTOR  
public GamePanel() {

    setSize(WIDTH, HEIGHT);
    setBackground(new Color(240, 255, 255));

    // right pressed

    KeyStroke ks1 = KeyStroke.getKeyStroke(KeyEvent.VK_RIGHT, 0, false);

    InputMap im1 = getInputMap(WHEN_IN_FOCUSED_WINDOW);
    ActionMap am1 = getActionMap();

    im1.put(ks1, "right.pressed");
    am1.put("right.pressed", new MoveHorizontialAction(HorizontalMovement.RIGHT));


    // right released

    KeyStroke ks2 = KeyStroke.getKeyStroke(KeyEvent.VK_RIGHT, 0, true);

    InputMap im2 = getInputMap(WHEN_IN_FOCUSED_WINDOW);
    ActionMap am2 = getActionMap();

    im2.put(ks2, "right.relesed");
    am2.put("right.relesed", new MoveHorizontialAction(HorizontalMovement.NONE));

    // left pressed

    KeyStroke ks3 = KeyStroke.getKeyStroke(KeyEvent.VK_LEFT, 0, false);

    InputMap im3 = getInputMap(WHEN_IN_FOCUSED_WINDOW);
    ActionMap am3 = getActionMap();

    im3.put(ks3, "left.pressed");
    am3.put("left.pressed", new MoveHorizontialAction(HorizontalMovement.LEFT));

    // left released

    KeyStroke ks4 = KeyStroke.getKeyStroke(KeyEvent.VK_LEFT, 0, true);

    InputMap im4 = getInputMap(WHEN_IN_FOCUSED_WINDOW);
    ActionMap am4 = getActionMap();

    im4.put(ks4, "left.relesed");
    am4.put("left.relesed", new MoveHorizontialAction(HorizontalMovement.NONE));


    // each 15 ms       
    timer = new Timer(15, new TimeListener());
    timer.start();

}

// PADDLE 
@Override
protected void paintComponent(Graphics g) {

    super.paintComponent(g);
    Graphics2D g2 = (Graphics2D) g;

    g2.setRenderingHint(RenderingHints.KEY_ANTIALIASING,
          RenderingHints.VALUE_ANTIALIAS_ON);

    g.setColor(new Color(201, 51, 51));
    g.fillRoundRect(x, PADDLE_Y, PADDLE_W, PADDLE_H, PADDLE_ARC, PADDLE_ARC);   
 }

// Time Listener

protected class TimeListener implements ActionListener {

    @Override
    public void actionPerformed(ActionEvent e) {

        if ( horizontalMovement == HorizontalMovement.RIGHT )
            x = x + 2;

        if ( horizontalMovement == HorizontalMovement.LEFT )
            x = x - 2;

        if ( x < 0 ) 
            x = 0;
        else if ( x > 520 ) 
            x = 520;

        repaint();
    }

}

// ACTION FOR ActionMap
protected class MoveHorizontialAction extends AbstractAction {

    private HorizontalMovement movement;

    public MoveHorizontialAction(HorizontalMovement movement) {
        this.movement = movement;
    }

    @Override
    public void actionPerformed(ActionEvent e) {
        horizontalMovement = movement;
    }
}   
}

主要代码:

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

public class MainFrame extends JFrame{

public MainFrame() {

    // size
    setSize(600, 500);
    setLocationRelativeTo(null);
    setDefaultCloseOperation( JFrame.EXIT_ON_CLOSE);    


    // remove borders
    setUndecorated(true);
    getRootPane().setBorder(BorderFactory.createMatteBorder(2, 2, 2, 2, new Color(63, 134, 145)));

    getContentPane().add( new GamePanel());

    setVisible(true);       
}

public static void main(String[] args) {

    new MainFrame();        
}
}

Answer 1

仅当链接方向处于 NONE 状态时，或者应该处于 NONE 状态时，情况如何

如果按向左键，则会是:

NONE->LEFT, LEFT

然后按右键:

LEFT->NONE, RIGHT

所以它会停止

@Override
public void actionPerformed(ActionEvent e) {
    if(horizontalMovement==HorizontalMovement.NONE ||
                 movement==HorizontalMovement.NONE){
        horizontalMovement = movement;
    }else{
        horizontalMovement = HorizontalMovement.NONE;
    }
}

未经测试，只是一个想法

编辑固定平滑

为了平滑运动，我使用了运动哈希集，其中包含所有 Activity 运动，因此如果它包含两个运动(右+左)，则将使用两个运动，从而导致此情况:

if ( movements.contains(HorizontalMovement.RIGHT) )
    x = x + 2;
if ( movements.contains(HorizontalMovement.LEFT) )
    x = x - 2;

两个条件都满足，x 保持x=(x+2)-2

此处为完整代码(类 GamePanel、MainFrame，无需编辑):

import java.awt.*;
import javax.swing.*;
import java.awt.event.*;
import java.util.HashSet;
public class GamePanel extends JPanel {

    // ENUM     
    public enum HorizontalMovement {
        NONE,
        LEFT,
        RIGHT
    }

    // CONSTANTS    
    private static final int WIDTH = 600;
    private static final int HEIGHT = 500;
    private static final int PADDLE_Y = 475;
    private static final int PADDLE_W = 80;
    private static final int PADDLE_H = 20;
    private static final int PADDLE_ARC = 15;
    private HashSet<HorizontalMovement> movements = new HashSet<HorizontalMovement>();

    // PROPERTIES   
    int x = 0;
    private Timer timer;

    // CONSTRUCTOR  
    public GamePanel() {

        setSize(WIDTH, HEIGHT);
        setBackground(new Color(240, 255, 255));

        // right pressed

        KeyStroke ks1 = KeyStroke.getKeyStroke(KeyEvent.VK_RIGHT, 0, false);

        InputMap im1 = getInputMap(WHEN_IN_FOCUSED_WINDOW);
        ActionMap am1 = getActionMap();

        im1.put(ks1, "right.pressed");
        am1.put("right.pressed", new MoveHorizontialAction(true,HorizontalMovement.RIGHT));

        // right released
        KeyStroke ks2 = KeyStroke.getKeyStroke(KeyEvent.VK_RIGHT, 0, true);
        InputMap im2 = getInputMap(WHEN_IN_FOCUSED_WINDOW);
        ActionMap am2 = getActionMap();

        im2.put(ks2, "right.relesed");
        am2.put("right.relesed", new MoveHorizontialAction(false,HorizontalMovement.RIGHT));

        // left pressed

        KeyStroke ks3 = KeyStroke.getKeyStroke(KeyEvent.VK_LEFT, 0, false);

        InputMap im3 = getInputMap(WHEN_IN_FOCUSED_WINDOW);
        ActionMap am3 = getActionMap();

        im3.put(ks3, "left.pressed");
        am3.put("left.pressed", new MoveHorizontialAction(true,HorizontalMovement.LEFT));

        // left released

        KeyStroke ks4 = KeyStroke.getKeyStroke(KeyEvent.VK_LEFT, 0, true);

        InputMap im4 = getInputMap(WHEN_IN_FOCUSED_WINDOW);
        ActionMap am4 = getActionMap();

        im4.put(ks4, "left.relesed");
        am4.put("left.relesed", new MoveHorizontialAction(false,HorizontalMovement.LEFT));

        // each 15 ms       
        timer = new Timer(15, new TimeListener());
        timer.start();

    }

    // PADDLE 
    @Override
    protected void paintComponent(Graphics g) {

        super.paintComponent(g);
        Graphics2D g2 = (Graphics2D) g;

        g2.setRenderingHint(RenderingHints.KEY_ANTIALIASING,
            RenderingHints.VALUE_ANTIALIAS_ON);

        g.setColor(new Color(201, 51, 51));
        g.fillRoundRect(x, PADDLE_Y, PADDLE_W, PADDLE_H, PADDLE_ARC, PADDLE_ARC);   
    }

    // Time Listener

    protected class TimeListener implements ActionListener {

        @Override
        public void actionPerformed(ActionEvent e) {

            if ( movements.contains(HorizontalMovement.RIGHT) )
                x = x + 2;

            if ( movements.contains(HorizontalMovement.LEFT) )
                x = x - 2;

            if ( x < 0 ) 
                x = 0;
            else if ( x > 520 ) 
                x = 520;

            repaint();
        }

    }

    // ACTION FOR ActionMap
    protected class MoveHorizontialAction extends AbstractAction {

        private HorizontalMovement movement;
        private boolean add=true;
        public MoveHorizontialAction(boolean add,HorizontalMovement movement) {
            this.movement = movement;
            this.add = add;
        }

        @Override
        public void actionPerformed(ActionEvent e) {
            if(add){
                //System.out.println("Add: "+movement.name());
                movements.add(movement);
            }else{
                //System.out.println("Rem: "+movement.name());
                movements.remove(movement);
            }
        }
    }   
}

不要害怕询问有关此代码的问题