如何在java中输入键盘后更改图像？

Question

我有以下代码向您展示：

ALTER TABLE `example` ADD IGNORE...

我的问题是我只要用户在键盘上按住右箭头就会更改图像，当用户放开它时，它会返回默认图像。请告诉我该怎么做。我认为它是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。

Answer 1

1. 覆盖paintComponent而不是paint。有关详细信息，请参阅Performing Custom Painting和Painting in AWT and Swing
2. 使用密钥绑定API代替KeyListener，它会减少问题。有关详细信息，请参阅How to Use Key Bindings

基本上，您可以只使用Image作为类实例字段，该字段由paintComponent方法绘制。按下该键后，您可以将图像更改为＆＃34;移动图像＆＃34;当它被释放时，将其更改回＆＃34;默认图像＆＃34;

更新了示例



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);
        }

    }

}