Why Are My Images Not Loading in Java Swing?

[UltimateSomni]

The error: "Exception in thread "main" java.lang.NullPointerException
at javax.swing.ImageIcon.<init>(ImageIcon.java:167)
at Buttons.<init>(Windows.java:12)
at Buttons.main(Windows.java:38)
Java Result: 1"

The Windows.java code:
_______________________________________

import javax.swing.*;

class Buttons extends JFrame
{
JPanel pnl = new JPanel();

ClassLoader ldr = this.getClass().getClassLoader();

java.net.URL tickURL = ldr.getResource("tick.png");
java.net.URL crossURL = ldr.getResource("cross.png");

ImageIcon tick = new ImageIcon( tickURL ); //LINE 12
ImageIcon cross = new ImageIcon( crossURL );

//ImageIcon tick = new ImageIcon( "tick.png" );
//ImageIcon cross = new ImageIcon( "cross.png" );

JButton btn = new JButton( "Click Me" );
JButton tickBtn = new JButton( tick );
JButton crossBtn = new JButton( "STOP", cross );

public Buttons()
{
super("Swing Window");
setSize( 500,200 );
setDefaultCloseOperation( EXIT_ON_CLOSE );
add(pnl);

pnl.add( btn );
pnl.add( tickBtn );
pnl.add( crossBtn );

setVisible( true );
}

public static void main ( String[] args )
{
Buttons gui = new Buttons();//LINE 38
}
}
_____________________________________________

and line 167 of ImageIcon.java looks like this :


public ImageIcon (URL location) {
this(location, location.toExternalForm()); //line 167
}

_______________________________________________

according to the book this should work

 

[I like Serena]

Hi UltimateSomni!

It means that the program can't find the .png images.

Put tick.png and cross.png into the directory where you run your program and you should be fine.

 

[Borg]

You should use the commented out ImageIcon constructors that you created instead of the the 5 lines of code where you're trying to pass java.net.URL instances into ImageIcon.

ImageIcon tick = new ImageIcon( "tick.png" );
ImageIcon cross = new ImageIcon( "cross.png" );

If you're not sure where the program is trying to find your images, use this after your super() call:

System.out.println("tick: " + tick);
System.out.println("cross : " + cross);

That will print out the complete path where the program is looking for the images. If your images aren't in the directory where the program is looking, Java will just create an empty image which is why you won't see anything.

Finally, you should put the add(pnl); call after you add all of the buttons to the pnl object. It doesn't break in this case but it could cause problems.

 

[kevinfrankly]

//ImageIcon tick = new ImageIcon( "tick.png" );
//ImageIcon cross = new ImageIcon( "cross.png" );

erasing that "//" maybe going to solve your problem .

 

[Borg]

//ImageIcon tick = new ImageIcon( "tick.png" );
//ImageIcon cross = new ImageIcon( "cross.png" );

erasing that "//" maybe going to solve your problem .

If he does that without commenting out the other pair of ImageIcon instances, he will have more problems.

 

[UltimateSomni]

Hi UltimateSomni!

It means that the program can't find the .png images.

Put tick.png and cross.png into the directory where you run your program and you should be fine.

This works

 

[kevinfrankly]

If he does that without commenting out the other pair of ImageIcon instances, he will have more problems.

wow, thanks for your correction . so the only problem is because the image (.png) isn't in the class directory, isn't it ?