如何在java中输入键盘后更改图像？ [英] How to change an image after a keyboard input in java?

问题描述

我有以下代码向您展示：

I have the following code to show you:

public class Test extends JPanel implements ActionListener, KeyListener
{
     Timer tm = new Timer(5, this);
     int x = 0, y = 0, velX = 0, velY = 0; 



public Test()
{
    tm.start(); //starts the timer
    addKeyListener(this);
    setFocusable(true);
    setFocusTraversalKeysEnabled(false); 
}




public void paint(Graphics g)
{
    super.paint(g);
    ImageIcon s = new ImageIcon("C:\\Users\\Owner\\Pictures\\Stick.jpg");
    s.paintIcon(this,g,x,y);

}




public void actionPerformed(ActionEvent e)
{
    if (x < 0)
    {
        velX = 0;
        x = 0;
    }

    if (x > 630)
    {
        velX = 0;
        x = 630;
    }

    if(y < 0)
    {
        velY = 0;
        y = 0;
    }

    if(y > 430)
    {
        velY = 0;
        y = 430;
    }
    x = x + velX;
    y = y + velY;
    repaint();
}




public void keyPressed(KeyEvent e)
{
    int c = e.getKeyCode();

    if (c == KeyEvent.VK_LEFT)
    {
        velX = -1;
        velY = 0;

    }
    if(c == KeyEvent.VK_UP)
    {
        velX = 0;
        velY = -1;

    }
    if(c == KeyEvent.VK_RIGHT)
    {
        velX = 1;
        velY = 0;
    }
    if(c == KeyEvent.VK_DOWN)
    {
        velX = 0;
        velY = 1;
    }
}

public void keyTyped(KeyEvent e){}
public void keyReleased(KeyEvent e)
{
    velX = 0;
    velY = 0;
}





public static void main(String[] args)
{
    Test t = new Test();
    JFrame jf = new JFrame();
    jf.setTitle("Tutorial");
    jf.setSize(700, 600);
    jf.setDefaultCloseOperation(JFrame.EXIT_ON_CLOSE);
    jf.add(t);
    jf.setVisible(true);
}

我的问题是我只要用户在键盘上按住右箭头就会改变图像，当用户放开时，它返回默认图像。请告诉我该怎么做。我认为这是Graphics类中的一系列if语句，然后将它们调用到键输入，但我不太确定。我也在使用Eclipse。谢谢。

My problem is I whenever the user holds the right arrow on the keyboard it changes an image, when the user lets go it goes back the the default image. Please tell me how to do that. I think it is a series of if statements in the Graphics class then calling them to the key input but I'm not quite sure. I am also using Eclipse. Thank You.

推荐答案

1. 覆盖 paintComponent 而不是 paint 。请参阅执行自定义绘画和在AWT和Swing中绘画以获取更多详细信息


2. 使用键绑定API而不是 KeyListener ，它会减少问题。有关更多详细信息，请参见如何使用密钥绑定。

1. Override paintComponent instead of paint. See Performing Custom Painting and Painting in AWT and Swing for more details
2. Use the key bindings API instead of KeyListener, it will cause you less issues. See How to Use Key Bindings for more details

基本上，你可以将 Image 作为一个类实例字段，它被绘制通过 paintComponent 方法。按下该键后，您可以将图像更改为移动图像，当它被释放时，将其更改回默认图像

Essentially, you could just have a Image as a class instance field, which was painted by the paintComponent method. When the key was pressed, you would change the image to the "move image" and when it was released, change it back to the "default image"

import java.awt.Dimension;
import java.awt.EventQueue;
import java.awt.Graphics;
import java.awt.Graphics2D;
import java.awt.event.ActionEvent;
import java.awt.event.ActionListener;
import java.awt.event.KeyEvent;
import java.awt.image.BufferedImage;
import java.io.IOException;
import javax.imageio.ImageIO;
import javax.swing.AbstractAction;
import javax.swing.Action;
import javax.swing.ActionMap;
import javax.swing.InputMap;
import javax.swing.JComponent;
import javax.swing.JFrame;
import javax.swing.JPanel;
import javax.swing.KeyStroke;
import javax.swing.Timer;
import javax.swing.UIManager;
import javax.swing.UnsupportedLookAndFeelException;

public class Test {

    public static void main(String[] args) {
        new Test();
    }

    public Test() {
        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 TestPane());
                frame.pack();
                frame.setLocationRelativeTo(null);
                frame.setVisible(true);
            }
        });
    }

    public interface Mover {

        public enum Direction {

            LEFT, RIGHT, NONE;
        }

        public void setDirection(Direction direction);

        public Direction getDirection();

    }

    public class TestPane extends JPanel implements Mover {

        private BufferedImage left;
        private BufferedImage right;
        private BufferedImage stand;

        private BufferedImage current;
        private Direction direction = Direction.NONE;
        private int xPos;
        private int yPos;

        public TestPane() {
            try {
                left = ImageIO.read(getClass().getResource("/Left.png"));
                right = ImageIO.read(getClass().getResource("/Right.png"));
                stand = ImageIO.read(getClass().getResource("/Stand.png"));
                current = stand;
                xPos = 100 - (current.getWidth() / 2);
                yPos = 100 - (current.getHeight() / 2);
            } catch (IOException exp) {
                exp.printStackTrace();
            }

            bindKeyStrokeTo(WHEN_IN_FOCUSED_WINDOW, "move.left", KeyStroke.getKeyStroke(KeyEvent.VK_LEFT,   0, false), new MoveAction(this, Direction.LEFT));
            bindKeyStrokeTo(WHEN_IN_FOCUSED_WINDOW, "stop.left", KeyStroke.getKeyStroke(KeyEvent.VK_LEFT,   0, true), new MoveAction(this, Direction.NONE));

            bindKeyStrokeTo(WHEN_IN_FOCUSED_WINDOW, "move.right", KeyStroke.getKeyStroke(KeyEvent.VK_RIGHT, 0, false), new MoveAction(this, Direction.RIGHT));
            bindKeyStrokeTo(WHEN_IN_FOCUSED_WINDOW, "stop.right", KeyStroke.getKeyStroke(KeyEvent.VK_RIGHT, 0, true), new MoveAction(this, Direction.NONE));

            Timer timer = new Timer(40, new ActionListener() {
                @Override
                public void actionPerformed(ActionEvent e) {
                    updatePosition();
                    repaint();
                }
            });
            timer.start();
        }

        protected void bindKeyStrokeTo(int condition, String name, KeyStroke keyStroke, Action action) {
            InputMap im = getInputMap(condition);
            ActionMap am = getActionMap();

            im.put(keyStroke, name);
            am.put(name, action);
        }

        @Override
        public Direction getDirection() {
            return direction;
        }

        @Override
        public void setDirection(Direction direction) {
            this.direction = direction;
        }

        protected void updatePosition() {

            switch (getDirection()) {
                case LEFT:
                    current = left;
                    xPos -= 1;
                    break;
                case RIGHT:
                    current = right;
                    xPos += 1;
                    break;
                case NONE:
                    current = stand;
                    break;
            }

            if (xPos < 0) {
                xPos = 0;
                current = stand;
            } else if (xPos + current.getWidth() > getWidth()) {
                current = stand;
                xPos = getWidth() - current.getWidth();
            }

        }

        @Override
        public Dimension getPreferredSize() {
            return new Dimension(200, 200);
        }

        @Override
        protected void paintComponent(Graphics g) {
            super.paintComponent(g);
            Graphics2D g2d = (Graphics2D) g.create();
            g2d.drawImage(current, xPos, yPos, this);
            g2d.dispose();
        }

    }

    public class MoveAction extends AbstractAction {

        private Mover mover;
        private Mover.Direction direction;

        public MoveAction(Mover mover, Mover.Direction direction) {
            this.mover = mover;
            this.direction = direction;
        }

        @Override
        public void actionPerformed(ActionEvent e) {
            mover.setDirection(direction);
        }

    }

}

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