In Java/Android a static variable or constant will not be garbage collected. It just stays there once the class that holds it is loaded via a class loader. The class loader is afaik always the same for all classes inside your app and its the one that has static references to all your classes (to e.g. MyInnerClass.class). Since the class loader does not go away your classes won’t do that either since they are referenced & therefore not garbage collectable.
Like in your example
public class SomeClass extends SurfaceView {
private static Context myContext;
public MyInnerClass(Context context){
myContext = context; // This is bad.
}
}
That is indeed bad. Even if no reference to SomeClass exists (e.g. the Activity that showed your custom SurfaceView has ended) the static reference to the Context (and any other static variable / constant in SomeClass will remain. You can consider all of them leaked since it is not possible to garbage collect that Context etc. If you have a regular variable reference something then once the instance that contains that variable has no more references to it the whole instance including its references to other things can and will be garbage collected. Java can even handle circular references fine.
For constants you want that to happen and it is usually not bad since the amount of constants and the amount of memory they occupy is not large. Also constants don’t (should not) reference other instances that take up large amounts of memory like Context or Bitmap.
Besides the possibility to create memory leaks through static variables you may also create problems if you don’t want to have only a single thing for all instances at the same time. For example if you save the Bitmap of your SurfaceView in a static variable you can’t have two different images. Even if the two SurfaceViews are not displayed at the same time you could run into problems since each new instance will probably overwrite the old image and if you go back to the other SurfaceView you unexpectedly show the wrong image. I am almost sure you don’t want to use static here.
The fact that your inner class is a static class does not mean that you have to use static variables – it just means that it behaves more like a static method since it can’t use the instance variables (the ones that are not static) in your class.
To avoid memory leaks you simply should not use static variables at all. There is no need to use them unless you do special stuff (e.g. counting instances of a class). Constants are fine.