Java KeyListener口吃

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.对于每个平台,它可以是不同的,并且用户也可以对其进行定制.

而是使用Timer来安排事件.在keyPressed上启动Timer并在keyReleased上停止Timer.

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",-3);
        navigation.addAction("DOWN",3);

        navigation.addAction("A",-5,0);
        navigation.addAction("S",5,0);
        navigation.addAction("Z",-5);
        navigation.addAction("X",5);
        navigation.addAction("V",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,其中事件的顺序为keyPressed,keyPressed,keyPressed … keyReleased.

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