java - 在java中加载图像时遇到问题，有人能看看出了什么问题吗？

Question

import java.awt.Graphics;
import java.awt.Graphics2D;
import java.awt.Image;
import java.awt.RenderingHints;

import javax.swing.ImageIcon;
import javax.swing.JFrame;

public class MainWindow extends JFrame{

    public static void main(String[] args) {

        JFrame mainWindow = new JFrame("Siege Arena");
        mainWindow.setResizable(false);
        mainWindow.setVisible(true);
        mainWindow.setDefaultCloseOperation(JFrame.EXIT_ON_CLOSE);
        mainWindow.setSize(500, 500);
        loadpics();

    }   

    Image bg;

    public void loadpics(){
        bg = new ImageIcon("C:\\test\\Background.png").getImage();
        repaint();

    }
    public void paint(Graphics g){
        g.drawImage(bg,0,0,null);

    }



}

我想做的就是创建一个 JFrame 并在其上加载一个简单的图像，我到底该怎么做。我在这里尝试过，但失败了。有人可以帮助我吗？

Answer 1

Can someone see what is wrong?

• 从 JFrame 扩展，您不会添加任何新功能，并且会将自己锁定在该组件的单一使用中
• 覆盖顶级容器的paint，例如JFrame，打破绘制链非常容易(就像您所做的那样)，这会带来无穷无尽的问题
• 不调用 super.paint 并破坏绘制链
• 未将 ImageObserver 传递给 ImageIcon
• 当您尝试加载图像时引用了错误的 MainWindow 实例。

如果我“猜测”正确，您正在尝试将背景图像绘制到窗口中。如果是这样，那么您尝试的方法绝对不是解决问题的方法。

相反...

• 从扩展自 JPanel 的自定义组件开始
• 使用paintComponent方法绘制图像
• 考虑使用 ImageIO 而不是 ImageIcon。如果图像无法加载，ImageIO将会抛出异常。

例如...

import java.awt.Dimension;
import java.awt.EventQueue;
import java.awt.Graphics;
import java.awt.Graphics2D;
import java.awt.image.BufferedImage;
import java.io.File;
import java.io.IOException;
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;

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.setContentPane(new BackgroundPane());
                frame.pack();
                frame.setLocationRelativeTo(null);
                frame.setVisible(true);
            }
        });
    }

    public class BackgroundPane extends JPanel {

        private BufferedImage bg;

        public BackgroundPane() {
            try {
                bg = ImageIO.read(new File("C:\\test\\Background.png"));
            } catch (IOException ex) {
                ex.printStackTrace();
            }
        }

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

        @Override
        protected void paintComponent(Graphics g) {
            super.paintComponent(g);
            if (bg == null) {
                Graphics2D g2d = (Graphics2D) g.create();
                int x = (getWidth() - bg.getWidth()) / 2;
                int y = (getHeight() - bg.getHeight()) / 2;
                g2d.drawImage(bg, x, y, this);
                g2d.dispose();
            }
        }

    }

}

看一下:

• Painting in AWT and Swing
• Performing Custom Painting
• Reading/Loading an Image

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