无法在OSX上的Swing中显示图像

Question

我认为我有点白痴，因为我在一段时间内没有完成Swing编程，但我正在尝试绘制一个简单的图像来屏幕显示，我没有得到我期望的结果

public class ImageApp { 

    public static void main(String[] args) throws MalformedURLException, IOException { 
     final Image image = ImageIO.read(new File("/Library/WebServer/Documents/image.gif")); 

     final JPanel component = new JPanel(){ 

      public void paint(final Graphics g) { 
       System.out.println("Drawing image "+image.getWidth(null)+" "+image.getHeight(null)); 
       g.drawString("hello", 0,0); 
       g.drawImage(image,this.getWidth()/2,this.getHeight()/2, 100, 100, Color.blue,this); 
       super.paint(g); 
      } 
     }; 

     final JFrame frame = new JFrame(); 

     frame.add(component); 
     frame.setSize(100, 100); 

     frame.pack(); 
     frame.setVisible(true); 
    } 

} 

这呈现一个空白窗口，似乎没有大小为100,100。是否还需要执行其他一些步骤才能使图形出现在屏幕上，或者需要遵循的尺寸？

我使用JDK6上OSX 10.6

Answer 1

在Swing中，你应该重写paintComponent()，不paint()。

附录：例如，见下文。在评论中，@eugener提出了一个关于使用JLabel作为替代image container的优秀观点。

import java.awt.Dimension; 
import java.awt.EventQueue; 
import java.awt.Graphics; 
import java.awt.Image; 
import java.io.File; 
import java.io.IOException; 
import javax.imageio.ImageIO; 
import javax.swing.JFrame; 
import javax.swing.JPanel; 

public class ImageApp { 

    public static void main(String[] args) throws IOException { 
     final Image image = ImageIO.read(new File("image.jpg")); 
     EventQueue.invokeLater(new Runnable() { 

      @Override 
      public void run() { 
       final JPanel component = new JPanel() { 

        @Override 
        public void paintComponent(final Graphics g) { 
         g.drawImage(image, 0, 0, null); 
        } 

        @Override 
        public Dimension getPreferredSize() { 
         return new Dimension(
          image.getWidth(this), image.getHeight(this)); 
        } 
       }; 

       final JFrame frame = new JFrame(); 
       frame.setDefaultCloseOperation(JFrame.EXIT_ON_CLOSE); 
       frame.add(component); 
       frame.pack(); 
       frame.setVisible(true); 
      } 
     }); 
    } 
} 

Answer 2

试试这个：

public class ImageApp { 

    public static void main(String[] args) throws MalformedURLException, IOException { 
     final Image image = ImageIO.read(new File("/Library/WebServer/Documents/image.gif")); 

     final JPanel component = new JPanel() { 

      @Override 
      public void paintComponent(final Graphics g) { 
       super.paintComponent(g); 
       System.out.println("Drawing image " + image.getWidth(null) + " " + image.getHeight(null)); 
       g.drawString("hello", 0,10); 
       g.drawImage(image, this.getWidth()/2, this.getHeight()/2, 100, 100, Color.blue, this); 
      } 
     }; 

     final JFrame frame = new JFrame(); 

     frame.add(component); 
     frame.setSize(100, 100); 

     frame.setVisible(true); 
    } 
}