java - 图像背景，覆盖油漆？

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尝试覆盖绘画帮助:(

总是出错。我的代码在错误的地方吗？

我不知道应该将我的代码粘贴到哪里，我目前已将其公开。我是否忘记在我的 main 中放入一些东西？

如果有人能提供帮助那就太好了!

我的代码如下。

import java.io.File;
import java.io.IOException;
import javax.swing.*;
import java.awt.*;
import java.awt.event.*;
import javax.imageio.ImageIO;
import java.awt.Panel;



/**
 * Created by IntelliJ IDEA.
 * User: Cara
 * Date: 09/01/2015

 * Time: 15:52
 * Program using SWING components to create a Christmas themed Calculator.
 */
public class GridBag2 extends JFrame implements ActionListener
{





   private GridBagConstraints gBC = new GridBagConstraints();

   private JButton zeroButton = new JButton("0");
   private JButton oneButton = new JButton("1");
   private JButton twoButton = new JButton("2");
   private JButton threeButton = new JButton("3");
   private JButton fourButton = new JButton("4");
   private JButton fiveButton = new JButton("5");
   private JButton sixButton = new JButton("6");
   private JButton sevenButton = new JButton("7");
   private JButton eightButton = new JButton("8");
   private JButton nineButton = new JButton("9");

   private JButton addButton = new JButton("+");
   private JButton subButton = new JButton("−");
   private JButton multButton = new JButton(" X ");
   private JButton divideButton = new JButton(" ÷ ");
   private JButton equalButton= new JButton("=");
   private JButton clearButton = new JButton("C");


   private JTextArea input=new JTextArea("");

   public Image img;
   public JPanel panel;


   Double number1,number2,result;
   int add=0,sub=0,mult=0,divide=0;



   public GridBag2()
   {



      zeroButton.addActionListener(this);
      oneButton.addActionListener(this);
      twoButton.addActionListener(this);
      threeButton.addActionListener(this);
      fourButton.addActionListener(this);
      fiveButton.addActionListener(this);
      sixButton.addActionListener(this);
      sevenButton.addActionListener(this);
      eightButton.addActionListener(this);
      nineButton.addActionListener(this);

      addButton.addActionListener(this);
      subButton.addActionListener(this);
      multButton.addActionListener(this);
      divideButton.addActionListener(this);
      equalButton.addActionListener(this);
      clearButton.addActionListener(this);



      gBC.insets = new Insets(5, 5, 5, 5);



      gBC.gridx = 1;
      gBC.gridy = 0;
      gBC.gridwidth = 4;
      gBC.fill = GridBagConstraints.BOTH;
      panel.add(input, gBC);


      gBC.gridx = 2;
      gBC.gridy = 4;
      gBC.gridwidth = 1;
      panel.add(zeroButton, gBC);


      gBC.gridx = 1;
      gBC.gridy = 4;
      gBC.gridwidth = 1;
      panel.add(oneButton, gBC);

      gBC.gridx = 1;
      gBC.gridy = 3;
      gBC.gridwidth = 1;
      panel.add(twoButton, gBC);


      gBC.gridx = 2;
      gBC.gridy = 3;
      gBC.gridwidth = 1;
      panel.add(threeButton, gBC);

      gBC.gridx = 1;
      gBC.gridy = 2;
      gBC.gridwidth = 1;
      panel.add(fourButton, gBC);

      gBC.gridx = 2;
      gBC.gridy = 2;
      gBC.gridwidth = 1;
      panel.add(fiveButton, gBC);

      gBC.gridx = 3;
      gBC.gridy = 2;
      gBC.gridwidth = 1;
      panel.add(sixButton, gBC);

      gBC.gridx = 1;
      gBC.gridy = 1;
      gBC.gridwidth = 1;
      panel.add(sevenButton, gBC);

      gBC.gridx = 2;
      gBC.gridy = 1;
      gBC.gridwidth = 1;
      panel.add(eightButton, gBC);

      gBC.gridx = 3;
      gBC.gridy = 1;
      gBC.gridwidth = 1;
      panel.add(nineButton, gBC);

      gBC.gridx = 3;
      gBC.gridy = 3;
      gBC.gridwidth = 1;
      panel.add(addButton, gBC);

      gBC.gridx = 3;
      gBC.gridy = 4;
      gBC.gridwidth = 1;
      panel.add(subButton, gBC);

      gBC.gridx = 4;
      gBC.gridy = 1;
      gBC.gridwidth = 1;
      panel.add(divideButton, gBC);

      gBC.gridx = 4;
      gBC.gridy = 2;
      gBC.gridwidth = 1;
      panel.add(multButton, gBC);

      gBC.gridx = 4;
      gBC.gridy = 3;
      gBC.gridwidth = 1;
      panel.add(equalButton, gBC);

      gBC.gridx = 4;
      gBC.gridy = 4;
      gBC.gridwidth = 1;
      panel.add(clearButton, gBC);



      setVisible(true);
      setSize(335, 340);
      setDefaultCloseOperation(JFrame.EXIT_ON_CLOSE);
      input.setEditable(false);



      getContentPane().add(panel);


      try {
         img = ImageIO.read(new File("C:\\Users\\Cara\\Pictures\\christmas.jpg"));
      } catch (IOException e) {
         e.printStackTrace();
      }

      panel = new JPanel(new GridBagLayout()){
         @Override
         public void paintComponent(Graphics g){
            super.paintComponent(g);
            g.drawImage(img, 0, 0, this);
         }
      };











   }//ChristmasCalculator




   public void actionPerformed(ActionEvent e)
   {

      Object source = e.getSource();

      if(source==clearButton)
      {
         number1=0.0;
         number2=0.0;
         input.setText("");
      }//if

      if (source == zeroButton)
      {
         input.setText(input.getText() + "0");
      }//if

      if (source == oneButton)
      {
         input.setText(input.getText() + "1");
      }//if
      if (source == twoButton)
      {
         input.setText(input.getText() + "2");
      }//if
      if (source == threeButton)
      {
         input.setText(input.getText() + "3");
      }//if
      if (source == fourButton)
      {
         input.setText(input.getText() + "4");
      }//if
      if (source == fiveButton)
      {
         input.setText(input.getText() + "5");
      }//if
      if (source == sixButton)
      {
         input.setText(input.getText() + "6");
      }//if
      if (source == sevenButton)
      {
         input.setText(input.getText() + "7");
      }//if
      if (source == eightButton)
      {
         input.setText(input.getText() + "8");
      }//if
      if (source == nineButton)
      {
         input.setText(input.getText() + "9");
      }//if
      if (source == addButton)
      {
         number1=number_reader();
         input.setText("");
         add=1;
         sub=0;
         divide=0;
         mult=0;
      }//if
      if (source == subButton)
      {
         number1=number_reader();
         input.setText("");
         add=0;
         sub=1;
         divide=0;
         mult=0;
      }//if
      if (source == divideButton)
      {
         number1=number_reader();
         input.setText("");
         add=0;
         sub=0;
         divide=1;
         mult=0;
      }//if
      if (source == multButton)
      {
         number1=number_reader();
         input.setText("");
         add=0;
         sub=0;
         divide=0;
         mult=1;
      }//if
      if(source==equalButton)
      { number2=number_reader();

         if(add>0)
         {
            result=number1+number2;
            input.setText(Double.toString(result));
         }//if
      }//if

      if(source==equalButton)
      { number2=number_reader();

         if(sub>0)
         {
            result=number1-number2;
            input.setText(Double.toString(result));
         }//if
      }//if
      if(source==equalButton)
      { number2=number_reader();

         if(divide>0)
         {
            result=number1/number2;
            input.setText(Double.toString(result));
         }//if
      }//if
      if(source==equalButton)
      { number2=number_reader();

         if(mult>0)
         {
            result=number1*number2;
            input.setText(Double.toString(result));
         }//if
      }//if
   }//actionPerformed


   public double number_reader()
   {
      Double num1;
      String s;
      s=input.getText();
      num1=Double.valueOf(s);

      return num1;
   }//number_reader


   public static void main(String[] args){

      GridBag2 gui = new GridBag2();


   }//main



}//class

Answer 1

重写 JPanel 的 paintComponent() 方法，如下所示，然后删除您称为背景的 JLabel，因为不需要。

private Image img;
private JPanel panel;

try {
    img = ImageIO.read(new File("C:\\Users\\Cara\\Pictures\\christmas.jpg"));
} catch (IOException e) {
    e.printStackTrace();
}

panel = new JPanel(new GridBagLayout()){
    @Override
    public void paintComponent(Graphics g){
        super.paintComponent(g);
        g.drawImage(img, 0, 0, this);
    }
};

编辑:谢谢安德鲁·汤普森的建议。