Java 按下绑定键时不断移动精灵

Question

我创建了一个程序来创建一个正方形并将其绘制在 JPanel 上。还有控制方块移动的KeyBindings（w在上）（s在下）（a在左）（d在右）。我的问题是，当我按下键时，它移动了一个实例，犹豫了一下，然后继续移动。有什么办法可以防止运动的迟疑。

import javax.swing.JFrame;


public class MovingBox extends JFrame{

Panel panel;

public static void main(String args[]){

    MovingBox mb = new MovingBox();
}

public MovingBox(){

    super("Moving Box");
    setSize(800, 600);
    setDefaultCloseOperation(EXIT_ON_CLOSE);

    panel = new Panel();
    add(panel);

    setVisible(true);
}
}

这是我的面板 class。

import java.awt.Graphics;
import java.awt.Rectangle;
import java.awt.event.ActionEvent;
import java.awt.event.KeyEvent;

import javax.swing.*;


public class Panel extends JPanel{

Rectangle box;

public Panel(){

    box = new Rectangle(100, 100, 50, 50);

    getInputMap(JComponent.WHEN_IN_FOCUSED_WINDOW).put(
            KeyStroke.getKeyStroke(KeyEvent.VK_D, 0), "move left");
    getActionMap().put("move left", new MoveAction(3, 3));

    getInputMap(JComponent.WHEN_IN_FOCUSED_WINDOW).put(
            KeyStroke.getKeyStroke(KeyEvent.VK_A, 0), "move right");
    getActionMap().put("move right", new MoveAction(1, 3));

    getInputMap(JComponent.WHEN_IN_FOCUSED_WINDOW).put(
            KeyStroke.getKeyStroke(KeyEvent.VK_W, 0), "move up");
    getActionMap().put("move up", new MoveAction(0, 3));

    getInputMap(JComponent.WHEN_IN_FOCUSED_WINDOW).put(
            KeyStroke.getKeyStroke(KeyEvent.VK_S, 0), "move down");
    getActionMap().put("move down", new MoveAction(2, 3));
}

public void paintComponent(Graphics window){

    super.paintComponent(window);

    window.fillRect((int)box.getX(), (int)box.getY(), (int)box.getWidth(), (int)box.getHeight());
}

private class MoveAction extends AbstractAction{

    int direction;
    int speed;

    public MoveAction(int direction, int speed){

        this.direction = direction;
        this.speed = speed; 
    }

    public void actionPerformed(ActionEvent e){

        if(direction == 0){

            box.setLocation((int)box.getX(), (int)box.getY() - speed);

        }else if(direction == 1){

            box.setLocation((int)box.getX() - speed, (int)box.getY());

        }else if(direction == 2){

            box.setLocation((int)box.getX(), (int)box.getY() + speed);

        }else if(direction == 3){

            box.setLocation((int)box.getX() + speed, (int)box.getY());
        }

        repaint();
    }
}
}

任何帮助将不胜感激。谢谢。

Answer 1

要获得平滑的运动，您需要创建一个线程来处理运动。

为每个键 (w, a, s, d) 创建一个布尔变量，并在按下键时将其设置为 true，在释放键时将其设置为 false。只是一个简单的关键监听器。别忘了给jframe加上监听，检查jframe是否有焦点

private class InputListener implements KeyListener{
    @Override
    public void keyPressed(KeyEvent pressed) {

        //arrow keys
        if(pressed.getKeyCode() == 37){
            arrowLeft = true;
        }else if(pressed.getKeyCode() == 38){
            arrowUp = true;
        }else if(pressed.getKeyCode() == 39){
            arrowRight = true;
        }else if(pressed.getKeyCode() == 40){
            arrowDown = true;
        }

        //System.out.println(pressed.getKeyCode());
    }
    @Override
    public void keyReleased(KeyEvent released) {
        if(released.getKeyCode() == 37){
            arrowLeft = false;
        }
        if(released.getKeyCode() == 38){
            arrowUp = false;
        }
        if(released.getKeyCode() == 39){
            arrowRight = false;
        }
        if(released.getKeyCode() == 40){
            arrowDown = false;
        }
    }
    @Override
    public void keyTyped(KeyEvent arg0) {}
}

我用它来用箭头键移动，所以对于 wasd 移动你需要改变键码。您需要的第二件事是在按下某个键时移动正方形的后台线程。它根据经过的速度和时间计算运动，因此非常流畅。

long currTime = 0;
long lastTime = 0;

new Thread() {
    @Override
      public void run() {
        Thread.currentThread().setPriority(Thread.MIN_PRIORITY);

        while (true) {
           currTime = System.currentTimeMillis();
           long time = currTime - lastTime;

           int movePixel = (int) (speed * time);

           if (movePixel < 1 ) {
                            currPlayerTime -= time;
           }else{
               if(arrowLeft){
                     //move left by movePixel pixel
               }else if(arrowRight){
                     //move right by movePixel pixel
               }
               if(arrowUp){

               }else if(arrowDown){

               }     
             }

            lastTime = currTime;
        }
    }
}.start();

这可能不是最简单和最快的解决方案，但绝对是最好的:)

Answer 2

Is there a way to prevent to the hesitation of the movement.

您可以使用 Swing Timer 来安排动画。查看 Motion Using the Keyboard 的工作示例。

Java 按下绑定键时不断移动精灵

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