Java KeyListener 口吃 [英] Java KeyListener stutters

问题描述

我正在用 Java 制作一个非常简单的乒乓球游戏，并且我正在使用 KeyListener 进行此操作.我希望这样当用户按下键盘上的向左或向右键时，乒乓球块就会朝那个方向移动.这是一个足够简单的任务，但我发现当用户按住键时，块移动一次，停止一小段时间，然后继续移动直到用户释放键.我注意到当您尝试按住计算机上的字母键时会发生这种情况.如果我尝试按住a"键，计算机将执行以下操作:

I'm making a very simple pong game in java and I'm doing this using KeyListener. I want it so when the user presses the right or left keys on the keypad, the pong block goes in that direction. This is a simple enough task, but what I'm finding out is that when the user holds down the key, the block moves once, stops for a short time, then continues moving until the user releases the key. I notice this happens when you try to hold down a letter key on a computer. If I try to hold down the 'a' key, the computer will do:

[停顿] aaaaaaaaaaaaaaa

a [pause] aaaaaaaaaaaaaaaa

有什么办法可以禁用这种卡顿，因为它妨碍了我的小游戏的流畅游戏体验.快速修复将不胜感激.

Is there someway to disable this stutter, because it is getting in the way of smooth gameplay for my little game. A quick fix would be deeply appreciated.

推荐答案

我最初有一个关于 Key Bindings 的答案，但经过一些测试后我发现他们仍然有同样的口吃问题.

I originally had an answer about Key Bindings, but after a little testing I found that they still had the same stutter problem.

不要依赖操作系统的重复率.每个平台都可能有所不同，用户也可以对其进行自定义.

Don't rely on the repeat rate of the OS. It can be different for every platform and a user may also customize it.

改为使用计时器来安排事件.您在 keyPressed 上启动 Timer，在 keyReleased 上停止 Timer.

Instead use a Timer to schedule the event. You start the Timer on a keyPressed and stop the Timer on keyReleased.

import java.awt.*;
import java.awt.event.*;
import java.net.*;
import java.util.Map;
import java.util.HashMap;
import javax.imageio.ImageIO;
import javax.swing.*;

public class KeyboardAnimation implements ActionListener
{
    private final static String PRESSED = "pressed ";
    private final static String RELEASED = "released ";
    private final static Point RELEASED_POINT = new Point(0, 0);

    private JComponent component;
    private Timer timer;
    private Map<String, Point> pressedKeys = new HashMap<String, Point>();

    public KeyboardAnimation(JComponent component, int delay)
    {
        this.component = component;

        timer = new Timer(delay, this);
        timer.setInitialDelay( 0 );
    }

    public void addAction(String keyStroke, int deltaX, int deltaY)
    {
//      InputMap inputMap = component.getInputMap(JComponent.WHEN_IN_FOCUSED_WINDOW);
        InputMap inputMap = component.getInputMap();
        ActionMap actionMap = component.getActionMap();

        String pressedKey = PRESSED + keyStroke;
        KeyStroke pressedKeyStroke = KeyStroke.getKeyStroke( pressedKey );
        Action pressedAction = new AnimationAction(keyStroke, new Point(deltaX, deltaY));
        inputMap.put(pressedKeyStroke, pressedKey);
        actionMap.put(pressedKey, pressedAction);

        String releasedKey = RELEASED + keyStroke;
        KeyStroke releasedKeyStroke = KeyStroke.getKeyStroke( releasedKey );
        Action releasedAction = new AnimationAction(keyStroke, RELEASED_POINT);
        inputMap.put(releasedKeyStroke, releasedKey);
        actionMap.put(releasedKey, releasedAction);
    }

    private void handleKeyEvent(String keyStroke, Point moveDelta)
    {
        //  Keep track of which keys are pressed

        if (RELEASED_POINT == moveDelta)
            pressedKeys.remove( keyStroke );
        else
            pressedKeys.put(keyStroke, moveDelta);

        //  Start the Timer when the first key is pressed

        if (pressedKeys.size() == 1)
        {
            timer.start();
        }

        //  Stop the Timer when all keys have been released

        if (pressedKeys.size() == 0)
        {
            timer.stop();
        }
    }

    //  Invoked when the Timer fires

    public void actionPerformed(ActionEvent e)
    {
        moveComponent();
    }

    //  Move the component to its new location

    private void moveComponent()
    {
        int componentWidth = component.getSize().width;
        int componentHeight = component.getSize().height;

        Dimension parentSize = component.getParent().getSize();
        int parentWidth  = parentSize.width;
        int parentHeight = parentSize.height;

        //  Calculate new move

        int deltaX = 0;
        int deltaY = 0;

        for (Point delta : pressedKeys.values())
        {
            deltaX += delta.x;
            deltaY += delta.y;
        }


        //  Determine next X position

        int nextX = Math.max(component.getLocation().x + deltaX, 0);

        if ( nextX + componentWidth > parentWidth)
        {
            nextX = parentWidth - componentWidth;
        }

        //  Determine next Y position

        int nextY = Math.max(component.getLocation().y + deltaY, 0);

        if ( nextY + componentHeight > parentHeight)
        {
            nextY = parentHeight - componentHeight;
        }

        //  Move the component

        component.setLocation(nextX, nextY);
    }

    private class AnimationAction extends AbstractAction implements ActionListener
    {
        private Point moveDelta;

        public AnimationAction(String keyStroke, Point moveDelta)
        {
            super(PRESSED + keyStroke);
            putValue(ACTION_COMMAND_KEY, keyStroke);

            this.moveDelta = moveDelta;
        }

        public void actionPerformed(ActionEvent e)
        {
            handleKeyEvent((String)getValue(ACTION_COMMAND_KEY), moveDelta);
        }
    }

    public static void main(String[] args)
    {
        JPanel contentPane = new JPanel();
        contentPane.setLayout( null );

        Icon dukeIcon = null;

        try
        {
            dukeIcon = new ImageIcon( "dukewavered.gif" );
//          dukeIcon = new ImageIcon( ImageIO.read( new URL("http://duke.kenai.com/iconSized/duke4.gif") ) );
        }
        catch(Exception e)
        {
            System.out.println(e);
        }

        JLabel duke = new JLabel( dukeIcon );
        duke.setSize( duke.getPreferredSize() );
        duke.setLocation(100, 100);
        contentPane.add( duke );

        KeyboardAnimation navigation = new KeyboardAnimation(duke, 24);
        navigation.addAction("LEFT", -3,  0);
        navigation.addAction("RIGHT", 3,  0);
        navigation.addAction("UP",    0, -3);
        navigation.addAction("DOWN",  0,  3);

        navigation.addAction("A", -5,  0);
        navigation.addAction("S",  5,  0);
        navigation.addAction("Z",  0, -5);
        navigation.addAction("X",  0,  5);
        navigation.addAction("V",  5,  5);

        JFrame frame = new JFrame();
        frame.setDefaultCloseOperation( JFrame.EXIT_ON_CLOSE );
//      frame.getContentPane().add(new JTextField(), BorderLayout.SOUTH);
        frame.getContentPane().add(contentPane);
        frame.setSize(600, 600);
        frame.setLocationRelativeTo( null );
        frame.setVisible(true);
    }

}

此代码在 Windows 上进行了测试，其中事件的顺序是 keyPressed、keyPressed、keyPressed...keyReleased.

This code was tested on Windows where the order of events is keyPressed, keyPressed, keyPressed... keyReleased.

但是，我认为在 Mac(或 Unix)上，事件的顺序是 keyPressed、keyReleased、keyPressed、keyReleased...所以我不确定这段代码是否会比你当前的代码更好.

However, I think on a Mac (or Unix) the order of events is keyPressed, keyReleased, keyPressed, keyReleased... So I'm not sure if this code would works any better than your current code.

这篇关于Java KeyListener 口吃的文章就介绍到这了，希望我们推荐的答案对大家有所帮助，也希望大家多多支持IT屋！