在 JComponent 中的图像顶部绘制图像会擦除底部图像的一部分

Question

我正在制作一个 2d 游戏，我需要在另一个图像之上绘制一个图像。在我绘制第一张图片（较大的图片，jpg）后，第二张图片（较小的图片，png）从第二张图片到右下角的位置擦除。像这样：

我对此进行了一些调查，有人建议我使用缓冲图像，所以我对两个图像都这样做了，但问题仍然存在。这是我看过的 post：How to draw an image over another image?。我还看到有人建议使用 graphics2d，但我并没有真正理解使用它们的原因或如何使用它们。我是 java 图形和图像的新手，所以这可能是一个愚蠢的错误。这是我的代码。谢谢。

import java.awt.*;
import java.awt.event.*;
import java.net.*;
import javax.swing.*;
import java.util.ArrayList;
import java.awt.image.BufferedImage;
import javax.imageio.ImageIO;
import java.io.IOException;

public class DisplayExample extends JComponent
{
private BufferedImage backgroundImage;
private String backgroundName;

private BufferedImage image;  //image to draw
private int imageX;  //position of left edge of image
private int imageY;  //position of top edge of image

private JFrame frame;

public static void main(String[] args)
{
    DisplayExample example = new DisplayExample();
    example.run();
}

public DisplayExample()
{
    imageX = 200;
    imageY = 200;

    backgroundName = "backgroundShip.jpg";
    URL backgroundURL = getClass().getResource(backgroundName);
    if (backgroundURL == null)
        throw new RuntimeException("Unable to load:  " + backgroundName);
    try{backgroundImage = ImageIO.read(backgroundURL);}catch(IOException ioe){}
    //load image

    String fileName = "explosion.png";
    URL url = getClass().getResource(fileName);
    if (url == null)
        throw new RuntimeException("Unable to load:  " + fileName);
    //image = new ImageIcon(url).getImage();
    try{image = ImageIO.read(url);}catch(IOException ioe){}
    System.out.println(image instanceof BufferedImage);
    setPreferredSize(new Dimension(1040,500));  //set size of drawing region

    //need for keyboard input
    setFocusable(true);  //indicates that WorldDisp can process key presses

    frame = new JFrame();
    frame.getContentPane().add(this);
    frame.pack();
    frame.setVisible(true);
}

public void paintComponent(Graphics g)
{

    super.paintComponent(g);
    if(backgroundImage != null)
        g.drawImage(backgroundImage,0,0,getWidth(), getHeight(), null);
    g.drawImage(image, imageX, imageY, this);  
}

public void run()
{ 
    while(true)
    {
    imageY+=1;
    repaint();
    try{Thread.sleep(100);}catch(Exception e){}
    }
}

}

Answer 1

所以我使用了你的代码，添加了我自己的图像，它对我来说运行良好。

话虽如此，但您可以在某些方面进行改进：

您运行有阻塞事件调度线程或使用 run 方法将线程竞争条件引入代码的风险。您应该考虑改用 Swing Timer。有关详细信息，请参阅 How to use Swing Timers。这允许您安排在 EDT 上下文中调用的定期回调，从而更安全地更新 UI
您应该只在 EDT 上下文中创建或修改 UI 的状态，Swing 不是线程安全的。有关详细信息，请参阅 Initial Threads。当 UI 未在 EDT
缩放图像代价高昂，您应该避免在 paint 方法中这样做，而是缩放图像并保留对结果的引用，并在需要绘制时使用它。
您应该考虑使用键绑定 API 而不是 KeyListener，它将解决许多与使用 KeyListener 相关的问题。有关详细信息，请参阅 How to Use Key Bindings。

例如...

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 javax.imageio.ImageIO;
import javax.swing.JComponent;
import javax.swing.JFrame;
import javax.swing.Timer;
import javax.swing.UIManager;
import javax.swing.UnsupportedLookAndFeelException;

public class DisplayExample extends JComponent {

    private BufferedImage backgroundImage;
    private String backgroundName;

    private BufferedImage image;  //image to draw
    private int imageX;  //position of left edge of image
    private int imageY;  //position of top edge of image

    public static void main(String[] args) {
        EventQueue.invokeLater(new Runnable() {
            @Override
            public void run() {
                try {
                    UIManager.setLookAndFeel(UIManager.getSystemLookAndFeelClassName());
                } catch (ClassNotFoundException | InstantiationException | IllegalAccessException | UnsupportedLookAndFeelException ex) {
                    ex.printStackTrace();
                }

                DisplayExample example = new DisplayExample();

                JFrame frame = new JFrame("Testing");
                frame.setDefaultCloseOperation(JFrame.EXIT_ON_CLOSE);
                frame.add(example);
                frame.pack();
                frame.setLocationRelativeTo(null);
                frame.setVisible(true);
            }
        });
    }

    public DisplayExample() {
        imageX = 200;
        imageY = 200;

        try {
            backgroundImage = ImageIO.read(new File("..."));
        } catch (IOException ioe) {
            ioe.printStackTrace();
        }
        //load image

        try {
            image = ImageIO.read(new File("..."));
        } catch (IOException ioe) {
            ioe.printStackTrace();
        }

        //need for keyboard input
        //setFocusable(true);  //indicates that WorldDisp can process key presses
        // Use the key bindings API instead, causes less issues
        Timer timer = new Timer(100, new ActionListener() {
            @Override
            public void actionPerformed(ActionEvent e) {
                imageY += 1;
                repaint();
            }
        });
        timer.start();
    }

    @Override
    public Dimension getPreferredSize() {
        return backgroundImage == null ?  new Dimension(200, 200) : new Dimension(backgroundImage.getWidth(), backgroundImage.getHeight());
    }

    @Override
    public void paintComponent(Graphics g) {
        super.paintComponent(g);
        Graphics2D g2d = (Graphics2D) g.create();
        if (backgroundImage != null) {
            // Scaling is expensive, don't do it here
            int x = (getWidth() - backgroundImage.getWidth()) / 2;
            int y = (getHeight() - backgroundImage.getHeight()) / 2;
            g2d.drawImage(backgroundImage, x, y, this);
        }
        g2d.drawImage(image, imageX, imageY, this);
        g2d.dispose();
    }
}

在 JComponent 中的图像顶部绘制图像会擦除底部图像的一部分

Drawing an image on top of an image in a JComponent erases part of the bottom image

java

image

swing

bufferedimage

paintcomponent