java - 将缓冲图像移动到特定坐标

Question

我试图通过按箭头键来移动网格周围的蓝色方 block 。我已经设置了 KeyListener，但是当我重新绘制框架时，我必须移动框架才能更新。如何使其成为平滑的动画(将正方形从一个坐标移动到另一个坐标)？

示例:

if (keyCode == KeyEvent.VK_LEFT){
    x5=x5-xChange;
    frame.repaint();
}

我的图像是缓冲图像，并且全部设置为特定坐标。这是我的图形类:

public static class myGraphicsPanel extends JPanel {   
    public void paintComponent(Graphics g) { 
      super.paintComponent(g); 
      g.drawImage(block1,x1,y1,null);
      g.drawImage(block2,x2,y2,null);
      g.drawImage(block3,x3,y3,null);
      g.drawImage(block4,x4,y4,null);
      g.drawImage(block5,x5,y5,null);
      g.drawImage(block6,x6,y6,null);
      g.drawImage(block7,x7,y7,null);
      g.drawImage(block8,x8,y8,null);
      g.drawImage(blue,x9,y9,null);
}

Answer 1

你的问题缺少很多信息，屏幕是如何更新的？画面是如何创建的？对象之间有什么关系？

其中许多问题都可以通过 MCVE 来回答。

动画是随时间变化的幻觉。所以你需要一些东西。您需要某种方法来更改当前状态，并需要某种方法来随着时间的推移触发和更新 UI。

在 Swing 中执行此操作的最简单(也是最安全)的方法是使用 Swing 计时器

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.image.BufferedImage;
import java.io.File;
import java.io.IOException;
import java.util.Random;
import java.util.logging.Level;
import java.util.logging.Logger;
import javax.imageio.ImageIO;
import javax.swing.JFrame;
import javax.swing.JPanel;
import javax.swing.UIManager;
import javax.swing.UnsupportedLookAndFeelException;
import javax.swing.Timer;

public class TestAnimation {

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

    public TestAnimation() {
        EventQueue.invokeLater(new Runnable() {
            @Override
            public void run() {
                try {
                    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);
                } catch (IOException ex) {
                    ex.printStackTrace();
                }
            }
        });
    }

    public class TestPane extends JPanel {

        private BufferedImage img;

        private int xDelta, yDelta;
        private int xPos, yPos;

        public TestPane() throws IOException {
            img = ImageIO.read(new File("/Users/shane/Dropbox/MegaTokyo/thumnails/2.jpg"));
            Random rnd = new Random();
            do {
                xDelta = rnd.nextInt(4);
            } while (xDelta == 0);
            do {
                yDelta = rnd.nextInt(4);
            } while (yDelta == 0);
            if (rnd.nextBoolean()) {
                xDelta *= -1;
            }
            if (rnd.nextBoolean()) {
                yDelta *= -1;
            }

            xPos = (getPreferredSize().width - img.getWidth()) / 2;
            yPos = (getPreferredSize().height - img.getHeight()) / 2;

            Timer timer = new Timer(40, new ActionListener() {
                @Override
                public void actionPerformed(ActionEvent e) {
                    xPos += xDelta;
                    yPos += yDelta;
                    if (xPos + img.getWidth() > getWidth()) { 
                        xPos = getWidth() - img.getWidth();
                        xDelta *= -1;
                    } else if (xPos < 0) {
                        xPos = 0;
                        xDelta *= -1;
                    }
                    if (yPos + img.getHeight() > getHeight()) { 
                        yPos = getHeight() - img.getHeight();
                        yDelta *= -1;
                    } else if (yPos < 0) {
                        yPos = 0;
                        yDelta *= -1;
                    }

                    repaint();
                }
            });
            timer.start();
        }

        @Override
        public Dimension getPreferredSize() {
            return new Dimension(400, 400);
        }

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

    }

}

仔细看看Concurrency in Swing和 w to Use Swing Timers了解更多详情

但是，如何使用键盘执行此操作？令人惊讶的是，它非常相似。

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.KeyEvent;
import java.awt.image.BufferedImage;
import java.io.File;
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.JFrame;
import javax.swing.JPanel;
import javax.swing.KeyStroke;
import javax.swing.UIManager;
import javax.swing.UnsupportedLookAndFeelException;

public class TestAnimation {

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

    public TestAnimation() {
        EventQueue.invokeLater(new Runnable() {
            @Override
            public void run() {
                try {
                    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);
                } catch (IOException ex) {
                    ex.printStackTrace();
                }
            }
        });
    }

    public class TestPane extends JPanel {

        private BufferedImage img;
        private int xPos, yPos;

        public TestPane() throws IOException {
            img = ImageIO.read(new File("/Users/shane/Dropbox/MegaTokyo/thumnails/2.jpg"));

            xPos = (getPreferredSize().width - img.getWidth()) / 2;
            yPos = (getPreferredSize().height - img.getHeight()) / 2;

            addKeyBinding("up", KeyStroke.getKeyStroke(KeyEvent.VK_UP, 0), new KeyAction(0, -4));
            addKeyBinding("down", KeyStroke.getKeyStroke(KeyEvent.VK_DOWN, 0), new KeyAction(0, 4));
            addKeyBinding("left", KeyStroke.getKeyStroke(KeyEvent.VK_LEFT, 0), new KeyAction(-4, 0));
            addKeyBinding("right", KeyStroke.getKeyStroke(KeyEvent.VK_RIGHT, 0), new KeyAction(4, 0));
        }

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

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

        @Override
        public Dimension getPreferredSize() {
            return new Dimension(400, 400);
        }

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

        public class KeyAction extends AbstractAction {

            private int xDelta, yDelta;

            public KeyAction(int xDelta, int yDelta) {
                this.xDelta = xDelta;
                this.yDelta = yDelta;
            }

            @Override
            public void actionPerformed(ActionEvent e) {
                xPos += xDelta;
                yPos += yDelta;
                if (xPos + img.getWidth() > getWidth()) {
                    xPos = getWidth() - img.getWidth();
                } else if (xPos < 0) {
                    xPos = 0;
                }
                if (yPos + img.getHeight() > getHeight()) {
                    yPos = getHeight() - img.getHeight();
                } else if (yPos < 0) {
                    yPos = 0;
                }

                repaint();
            }

        }

    }

}

看看How to use key bindings和 How to use actions了解更多详情