无法在我的JPanel中绘制图像

Question

I'm having trouble painting an image in my GraphicsPanel (extension of JPanel). I tried loading from a file with the pathname, using getCodeBase(), getDocumentBase(), getResource(), and using BufferedImage. Is there any way to draw the image without having to make it an ImageIcon inside a JLabel?

package rpg;

import java.awt.Color;

import java.awt.Graphics;
import java.awt.event.MouseEvent;
import java.awt.event.MouseListener;
import java.awt.event.MouseMotionListener;
import javax.swing.JPanel;
import java.awt.Image;
import java.io.File;
import java.io.IOException;
import javax.imageio.ImageIO;
import javax.swing.ImageIcon;
import javax.swing.JLabel;
import java.awt.image.BufferedImage;

public class GraphicsPanel extends JPanel implements MouseListener, MouseMotionListener {
private WorldBuilder wb;
public int currentTileType = 0;//tile types. 0=bgtile, 1=object, 2=NPC
public String currentTileName = "";
public Image currentTile;

public GraphicsPanel() {
    super();
}

@Override
public void paintComponent(Graphics g) {
    super.paintComponent(g);
    g.setColor(Color.red);
    g.fillRect(0, 0, 720, 528);
    g.drawImage(currentTile, 100, 100, this);//Nothing gets drawn here
}

public void getParameters(WorldBuilder wb) {
    this.wb = wb;
    this.currentTileType = wb.currentTileType;
    this.currentTileName = wb.currentTileName;
    /*
    try {
        currentTile = ImageIO.read(new File("SpriteSheet.png"));
    } catch (IOException e) {
        System.out.println("failed");
    }
    */
    currentTile = new ImageIcon("SpriteSheet.png").getImage();
    repaint();
}

@Override
public void mouseClicked(MouseEvent e) {
    throw new UnsupportedOperationException("Not supported yet."); //To change body of generated methods, choose Tools | Templates.
}

@Override
public void mousePressed(MouseEvent e) {
    throw new UnsupportedOperationException("Not supported yet."); //To change body of generated methods, choose Tools | Templates.
}

@Override
public void mouseReleased(MouseEvent e) {
    throw new UnsupportedOperationException("Not supported yet."); //To change body of generated methods, choose Tools | Templates.
}

@Override
public void mouseEntered(MouseEvent e) {
    throw new UnsupportedOperationException("Not supported yet."); //To change body of generated methods, choose Tools | Templates.
}

@Override
public void mouseExited(MouseEvent e) {
    throw new UnsupportedOperationException("Not supported yet."); //To change body of generated methods, choose Tools | Templates.
}

@Override
public void mouseDragged(MouseEvent e) {
    throw new UnsupportedOperationException("Not supported yet."); //To change body of generated methods, choose Tools | Templates.
}

@Override
public void mouseMoved(MouseEvent e) {
    throw new UnsupportedOperationException("Not supported yet."); //To change body of generated methods, choose Tools | Templates.
}

}

Answer 1

Summary of comments:

• The SpriteSheet.png is not located within location that ImageIcon(String) would be able to find it. ImageIcon(String) expects that the String references a File on the file system, but SpriteSheet.png is stored within the application context ( src/rpg/SpriteSheet.png ), this makes it an embedded resource.
• Use Class#getResource to load embedded resources, in this case either getClass().getResource("SpriteSheet.png") or getClass().getResource("/rpg/SpriteSheet.png") to be be sure.
• Use ImageIO.read over ImageIcon . It will at least throw an IOException when the image can not be loaded for some reason, where as ImageIcon can fail silently.
• Make sure that the instance of GraphicsPanel which is loading the resources is the same instance that is on the screen

Answer 2

The following works for me. I took your code, and added the panel to a JFrame. Also, I call getParameters(); before adding the Panel to the JFrame.

import java.awt.Color;

import java.awt.Graphics;
import java.awt.event.MouseEvent;
import java.awt.event.MouseListener;
import java.awt.event.MouseMotionListener;
import javax.swing.JPanel;
import java.awt.Image;
import java.io.File;
import java.io.IOException;
import javax.imageio.ImageIO;
import javax.swing.ImageIcon;
import javax.swing.JFrame;
import javax.swing.JLabel;
import java.awt.image.BufferedImage;

public class GraphicsPanel extends JPanel implements MouseListener,
        MouseMotionListener {

    public static void main(String args[]) {
        GraphicsPanel s = new GraphicsPanel();
        s.getParameters();
        JFrame frame = new JFrame();
        frame.add(s);       
        frame.setVisible(true);     
    }

    /**
     * 
     */
    private static final long serialVersionUID = 1L;
    public int currentTileType = 0;//tile types. 0=bgtile, 1=object, 2=NPC
    public String currentTileName = "";
    public Image currentTile;

    public GraphicsPanel() {
        super();
    }

    @Override
    public void paintComponent(Graphics g) {
        super.paintComponent(g);
        g.drawImage(currentTile, 100, 100, this);//Nothing gets drawn here
    }

    public void getParameters() {
        currentTile = new ImageIcon("test.jpg").getImage();
        repaint();
    }

    @Override
    public void mouseDragged(MouseEvent arg0) {
        // TODO Auto-generated method stub

    }

    @Override
    public void mouseMoved(MouseEvent arg0) {
        // TODO Auto-generated method stub

    }

    @Override
    public void mouseClicked(MouseEvent arg0) {
        // TODO Auto-generated method stub

    }

    @Override
    public void mouseEntered(MouseEvent arg0) {
        // TODO Auto-generated method stub

    }

    @Override
    public void mouseExited(MouseEvent arg0) {
        // TODO Auto-generated method stub

    }

    @Override
    public void mousePressed(MouseEvent arg0) {
        // TODO Auto-generated method stub

    }

    @Override
    public void mouseReleased(MouseEvent arg0) {
        // TODO Auto-generated method stub

    }   
}