Re: ByteProcessor class pixel[] fieldl become NULL when closing associated ImagePlus windows

Posted by Wayne Rasband on
URL: http://imagej.273.s1.nabble.com/ByteProcessor-class-pixel-fieldl-become-NULL-when-closing-associated-ImagePlus-windows-tp3702343p3702344.html

> My plugin write some annotations into a ByteProcessor displayed
> in an ImagePlus (I use putPixel,drawString methods, etc.).
> My annotated ByteProcessor instance is stored as a field in a
> dedicated class so I can display it again and again in a new
> ImagePlus window if user unfortunatly close current image (I don't
> know how to prevent user closing ImagePlus windows ;).
>
> The null pointer exception occurs when user close the ImagePlus
> windows and continue working anyway. My ByteProcessor instance,
> is not null but sudently Null pointer error occurs in
> ij.process.ByteProcessor.putPixel method or any other ByteProcessor
> method using Pixel[] array field. A quick debug showed that this
> array is null since ImagePlus is closed although my ByteProcessor
> is still not null.
>
> Is-it a normal behaviour ? How can I troubleshoot my pb ?

ImageJ sets the pixel arrays to null when the window is closed to  
encourage garbage collection. You can prevent this from happening by  
making a setIgnoreFlush(true) call on each new ImagePlus you create.

-wayne