Loading resources like images while running project distributed as JAR archive
JavaSwingNullpointerexceptionAwtEmbedded ResourceJava Problem Overview
I am having a error for my GUI. Trying to set title bar icon then be included in a Runnable JAR.
BufferedImage image = null;
try {
image = ImageIO.read(getClass().getClassLoader().getResource("resources/icon.gif"));
}
catch (IOException e) {
e.printStackTrace();
}
frame.setIconImage(image);
Here is the error I am getting:
Exception in thread "main" java.lang.IllegalArgumentException: input == null!
at javax.imageio.ImageIO.read(Unknown Source)
at GUI.<init>(GUI.java:39)
at GUI.main(GUI.java:351)
The image is in the correct directory which "resources" folder is the root of the project file
Java Solutions
Solution 1 - Java
First of all, change this line :
image = ImageIO.read(getClass().getClassLoader().getResource("resources/icon.gif"));
to this :
image = ImageIO.read(getClass().getResource("/resources/icon.gif"));
More info, on as to where lies the difference between the two approaches, can be found on this thread - Different ways of loading a Resource
For Eclipse:
For NetBeans:
For IntelliJ IDEA:
-
Right-Click the src Folder of the Project. Select New -> Package
-
Under New Package Dialog, type name of the package, say resources. Click OK
-
Right Click resources package. Select New -> Package
-
Under New Package Dialog, type name of the package, say images. Click OK
-
Now select the image that you want to add to the project, copy it. Right click resources.images package, inside the IDE, and select Paste
-
Use the last link to check how to access this file now in Java code. Though for this example, one would be using
getClass().getResource("/resources/images/myImage.imageExtension");
-
Press Shift + F10, to make and run the project. The resources and images folders, will be created automatically inside the out folder.
If you are doing it manually :
- How to add Images to your Project
- How to Use Icons
- A Little extra clarification, as given in this answer's first code example.
QUICK REFERENCE CODE EXAMPLE(though for more detail consider, A little extra clarification link):
package swingtest;
import java.awt.*;
import java.awt.image.BufferedImage;
import java.io.IOException;
import javax.imageio.ImageIO;
import javax.swing.*;
/**
* Created with IntelliJ IDEA.
* User: Gagandeep Bali
* Date: 7/1/14
* Time: 9:44 AM
* To change this template use File | Settings | File Templates.
*/
public class ImageExample {
private MyPanel contentPane;
private void displayGUI() {
JFrame frame = new JFrame("Image Example");
frame.setDefaultCloseOperation(JFrame.DISPOSE_ON_CLOSE);
contentPane = new MyPanel();
frame.setContentPane(contentPane);
frame.pack();
frame.setLocationByPlatform(true);
frame.setVisible(true);
}
private class MyPanel extends JPanel {
private BufferedImage image;
public MyPanel() {
try {
image = ImageIO.read(MyPanel.class.getResource("/resources/images/planetbackground.jpg"));
} catch (IOException ioe) {
ioe.printStackTrace();
}
}
@Override
public Dimension getPreferredSize() {
return image == null ? new Dimension(400, 300): new Dimension(image.getWidth(), image.getHeight());
}
@Override
protected void paintComponent(Graphics g) {
super.paintComponent(g);
g.drawImage(image, 0, 0, this);
}
}
public static void main(String[] args) {
Runnable runnable = new Runnable() {
@Override
public void run() {
new ImageExample().displayGUI();
}
};
EventQueue.invokeLater(runnable);
}
}
Solution 2 - Java
There's a much easier way to load and set an image as a frame icon:
frame.setIconImage(
new ImageIcon(getClass().getResource("/resources/icon.gif")).getImage());
And thats all :)! You don't even have to use a try-catch block because ImageIcon
does not throw any declared exceptions. And due to getClass().getResource()
, it works both from file system and from a jar depending how you run your application.
If you need to check whether the image is available, you can check if the URL returned by getResource()
is null
:
URL url = getClass().getResource("/resources/icon.gif");
if (url == null)
System.out.println( "Could not find image!" );
else
frame.setIconImage(new ImageIcon(url).getImage());
Solution 3 - Java
The image files must be in the directory resources/
in your JAR, as shown in How to Use Icons and this example for the directory named images/
.