adding background pic to JFrame

问题

I'm trying to follow this answer to add a background picture to a JFrame and I'm getting a weird error. While debugging my url is coming back null and I get a window that pops up saying "Class File Editor" source not found the source attachment does not contain the source for the file Launcher.class you can change the source attachment by clicking Chang Attached Source below. What does that mean?

here's the code that I have so far:

import java.awt.Graphics;
import java.awt.image.BufferedImage;

import javax.swing.ImageIcon;
import javax.swing.JButton;
import javax.swing.JFrame;
import javax.swing.SwingUtilities;

public class DeluxKenoMainWindow extends JFrame 
{


   public DeluxKenoMainWindow()
   {
    initUI();   
   }

   public final void initUI()
   {
     setLayout(null);
     getContentPane().add(new BackgroundImage());
     int xCoord = 10;
     int yCoord = 10;
     Button[] button = new Button[80];
     for(int i = 0; i<80; i++)
     {
         String buttonName = "button" + i;
        if(i % 10 == 0)
        {
            xCoord = 10;
            yCoord +=40;
        }

        xCoord += 40;
        if(i % 40 == 0)
            yCoord += 8;


         button[i] = new Button(buttonName, xCoord, yCoord, i+1);

         getContentPane().add(button[i]);
     }


     setTitle("Delux Keno");
     setSize(500,500);

     setDefaultCloseOperation(JFrame.EXIT_ON_CLOSE);
     setLocationRelativeTo(null);

   }



   public static void main(String[] args)
   {
    SwingUtilities.invokeLater(new Runnable()
    {
        public void run()
        {
            System.setProperty("DEBUG_UI", "true");
            DeluxKenoMainWindow ex = new DeluxKenoMainWindow();
            ex.setVisible(true);
        }
    });
   }
   }


import javax.imageio.ImageIO;
import javax.swing.Icon;
import javax.swing.ImageIcon;
import javax.swing.JButton;
import java.io.*;

public class Button extends JButton {


    private String name;
    private int xCoord;
    private int yCoord;
    private final int xSize = 40;
    private final int ySize = 40;
    private int buttonNumber;
    private String picture;


    public Button(String inName, int inXCoord, int inYCoord, int inButtonNumber)
    {


      xCoord = inXCoord;
      yCoord = inYCoord;
      buttonNumber = inButtonNumber;
      picture = "graphics\\" + buttonNumber + "normal.png";



      super.setName(name);    
      super.setIcon(new ImageIcon(picture));
      super.setBounds(xCoord, yCoord, xSize, ySize);

    }



    }


import java.awt.Graphics;
import java.awt.image.BufferedImage;
import java.io.File;
import java.io.IOException;
import java.net.URL;


import javax.imageio.ImageIO;
import javax.swing.JPanel;


public class BackgroundImage extends JPanel{

    private BufferedImage img;
    private URL rUrl;
    public BackgroundImage()
    {
        super();

        try{
            rUrl = getClass().getResource("formBackground.png");
            img = ImageIO.read(rUrl);
        }
        catch(IOException ex)
        {
            ex.printStackTrace();
        }

    }

    @Override
    protected void paintComponent(Graphics g)
    {
        //super.paintComponent(g);
        g.drawImage(img, 0, 0, getWidth(), getHeight(), this);

    }

}

any sugesstions will be appriciated!!

回答1:

• set classpath by @Gagandeep Bali

• don't perform any FileIO in paintComponent, load this image one time as local variable, pass variable in paintComponent

• for Bingo, Minesweaper to use JToggleButton instead of JButton

回答2:

went at it a different way, using a JLabel. Here's my final code:

import java.awt.Graphics;
import java.awt.image.BufferedImage;

import javax.swing.ImageIcon;
import javax.swing.JButton;
import javax.swing.JFrame;
import javax.swing.JLabel;
import javax.swing.SwingUtilities;

public class DeluxKenoMainWindow extends JFrame 
{


   public DeluxKenoMainWindow()
   {
    initUI();   
   }

   public final void initUI()
   {
     setLayout(null);
     JLabel background = new JLabel(new ImageIcon ("graphics\\formBackground.png"));

     background.setBounds(0,0,600,600);

     //getContentPane().add(new BackgroundImage());
    int xCoord = 85;
     int yCoord = 84;
     Button[] button = new Button[80];
     for(int i = 0; i<80; i++)
     {
         String buttonName = "button" + i;
        if(i % 10 == 0)
        {
            xCoord = 12;
            yCoord +=44;
        }


        if(i % 40 == 0)
            yCoord += 10;


         button[i] = new Button(buttonName, xCoord, yCoord, i+1);
         xCoord += 42;
         getContentPane().add(button[i]);
     }

     add(background);
     setTitle("Delux Keno");
     setSize(600,600);

     setDefaultCloseOperation(JFrame.EXIT_ON_CLOSE);
     setLocationRelativeTo(null);

   }



   public static void main(String[] args)
   {
    SwingUtilities.invokeLater(new Runnable()
    {
        public void run()
        {
            System.setProperty("DEBUG_UI", "true");
            DeluxKenoMainWindow ex = new DeluxKenoMainWindow();
            ex.setVisible(true);
        }
    });
   }
   }

回答3:

another problem I found is that you need to use setBounds() for the JPanel for it to have any size. To do it the first way I tried this is the updated BackgroundImage class:

import java.awt.Graphics;
import java.awt.image.BufferedImage;
import java.io.IOException;
import java.net.URL;

import javax.imageio.ImageIO;
import javax.swing.JPanel;


public class BackgroundImage extends JPanel{

    private BufferedImage img;
    private URL rUrl;
    public BackgroundImage()
    {
        super();

        try{
            rUrl = getClass().getResource("formBackground.png");

            img = ImageIO.read(rUrl);
        }
        catch(IOException ex)
        {
            ex.printStackTrace();
        }
        super.setBounds(0,0,600,600);

    }

    @Override
    protected void paintComponent(Graphics g)
    {
        super.paintComponent(g);
        g.drawImage(img, 0, 0, getWidth(), getHeight(), this);

    }

}

来源：https://stackoverflow.com/questions/13428796/adding-background-pic-to-jframe