在JFrame中显示.png图像？ [英] Show .png image in a JFrame?

问题描述

我有点卡住了。为什么不这样做？我只是得到一个错误说：

I am a little stuck. Why wont this work? I just get a error saying:

java.lang.NoSuchMethodError：main

java.lang.NoSuchMethodError: main

线程main中的异常

import java.awt.*; 
import javax.swing.*; 

@SuppressWarnings("serial")
public class ShowPNG extends JFrame
{    

  public void main(String arg) 
  { 
    if (arg == null ) {
        arg = "C:/Eclipse/workspace/ShowPNG/bin/a.png";
    }      
    JPanel panel = new JPanel(); 
    panel.setSize(500,640);
    panel.setBackground(Color.CYAN); 
    ImageIcon icon = new ImageIcon(arg); 
    JLabel label = new JLabel(); 
    label.setIcon(icon); 
    panel.add(label);
    this.getContentPane().add(panel); 
    this.setVisible(true);
  }

}

推荐答案

main需要是静态的，并且必须有一个String []的参数，而不是String。

main needs to be static, and must have an argument of String[], not String.

要修复这个在构造函数中的所有内容，例如

To fix this stick everything in a constructor, such as

import java.awt.*; 
import javax.swing.*; 

@SuppressWarnings("serial")
public class ShowPNG extends JFrame
{    
  private ShowPNG(String arg){
      if (arg == null ) {
        arg = "C:/Eclipse/workspace/ShowPNG/bin/a.png";
    }      
    JPanel panel = new JPanel(); 
    panel.setSize(500,640);
    panel.setBackground(Color.CYAN); 
    ImageIcon icon = new ImageIcon(arg); 
    JLabel label = new JLabel(); 
    label.setIcon(icon); 
    panel.add(label);
    this.getContentPane().add(panel); 
  }
  public static void main(String[] args) {
      new ShowPNG(args.length == 0 ? null : args[0]).setVisible(true); 
  }
}

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