Why won't my existing image draw to the screen?

Question

Basically here's the deal, I'm trying to load an image from a source file within the Project, but whenever I run the code nothing happens.

Can anyone shed some light on where I am going wrong, and maybe possibly how to get it to draw correctly?

Here's the code:

import java.awt.Graphics;
import java.awt.image.BufferedImage;
import java.io.File;
import java.io.IOException;
import javax.imageio.ImageIO;


public class EnterTile extends Tile {

public EnterTile() {
    setTile();
}

public void setTile() {

    try {
        BufferedImage img = ImageIO.read(new File("res\\BrokenFenceSwamp.gif"));
        Graphics g = img.getGraphics();
        g.drawImage(img, 1000, 1000, 8, 8, null);
    } catch (IOException e) {
        System.out.println("Error " + e);
    }
}

public static void main(String args[]) {
    EnterTile enterTile = new EnterTile();


}



}

Thanks for taking the time to read this.

You are not drawing on any UI component - [BufferedImage.getGraphics](http://docs.oracle.com/javase/7/docs/api/java/awt/Image.html#getGraphics())returns a graphics context to draw to an off-screen image. — Andreas Fester, Nov 24 '15 at 13:34
So I could essentially create a new JPanel and draw the image onto that? — PureShpongled, Nov 24 '15 at 13:37
Essentially, yes. See http://stackoverflow.com/questions/299495/how-to-add-an-image-to-a-jpanel — Andreas Fester, Nov 24 '15 at 13:38

Bogomil Dimitrov · Answer 1 · 2015-11-24T13:58:39.800

To load the image correctly you need to:

Have the res folder (where the image is stored) marked as a resource folder.
When you call the read() method of ImageIO, you need to pass a URL. To do that you need to use {className}.class.getResource({path}) (In your case ImageIO.read(EnterTile.class.getResource("/BrokenFenceSwamp.gif"));)

To draw the image you need to specify where. E.g. canvas if you are using awt library. You can try something like this:

public class Main {
    public static void main(String[] args) throws IOException {
        JFrame frame = new JFrame("Image Test");
        frame.setSize(400, 800);
        frame.setVisible(true);
        frame.setFocusable(true);
        frame.setDefaultCloseOperation(JFrame.EXIT_ON_CLOSE);
        frame.setLocationRelativeTo(null);
        frame.setResizable(false);

        Canvas canvas = new Canvas();
        canvas.setPreferredSize(new Dimension(400, 800));
        canvas.setMaximumSize(new Dimension(400, 800));
        canvas.setMinimumSize(new Dimension(400, 800));

        frame.add(canvas);
        frame.pack();

        canvas.createBufferStrategy(2);    
        BufferStrategy bs = canvas.getBufferStrategy();

        Graphics g = bs.getDrawGraphics();
        g.clearRect(0, 0, 400, 800);

        String path = "/BrokenFenceSwamp.gif";
        BufferedImage image = ImageIO.read(Main.class.getResource(path));

        g.drawImage(image, 0, 0, null);

        bs.show();
        g.dispose();
    }
}

Whilst using your code, a null pointer exception occurred during run-time at `Graphics g = bs.getDrawGraphics()`? — PureShpongled, Nov 24 '15 at 13:54
I edited the code so you need to first call `canvas.createBufferStrategy(2);` and after that `BufferStrategy bs = canvas.getBufferStrategy();`. The reason why I posted the code with the `if (bs == null)` condition is that I copied this code from a game of mine where the bufferStrategy is constantly being checked in a loop. But for drawing only once, first create the strategy by calling it on the canvas and afterwards `getBufferStrategy()` to instantiate the BufferStrategy variable. Tell me if it works :) — Bogomil Dimitrov, Nov 24 '15 at 13:58

score 1 · Accepted Answer · answered Nov 24 '15 at 13:38

Getting the Graphics of an image is a facility to be able to draw on images:

    BufferedImage img = ImageIO.read(new File("res\\BrokenFenceSwamp.gif"));

    Graphics g = img.getGraphics();
    g.drawString(img, 100, 100, "Hello World!");
    g.dispose();

    ImageIO.write(new File("res/TitledBFS.gif"));

It does not draw on the screen. Graphics can be memory (here), screen or printer.

To draw on the screen, one would make a full-screen window without title and borders, an on its background draw the image.

That would require becoming acquainted with swing or the newer JavaFX.

Why won't my existing image draw to the screen?

2 Answers2