Difference between code before and after super()

Question

Look at the sample codes below

@Override
protected void onPause() {
    ...some code here...
    super.onPause();
}

and

@Override
protected void onPause() {
    super.onPause();
    ...some code here...
}

When I asked about differences in code, I did not mean about the flow of execution, which is abvious.

So what is the real difference between these codes? When is it advised to use your code before super() call, and when to use your code after super() call? I guess there are situations when this does matter.

Answer 1

You should not place any of your code before super.onPause(), cause this method lets the system do what it needs to do to properly pause your application. Any code you want to execute in the onPause() callback should be placed after the call to super.onPause(). Hope this helps.

Quote from Activities:

Note: Your implementation of these lifecycle methods must always call the superclass implementation before doing any work, as shown in the examples above.

Answer 2

Had to chip in with this link to a thread with an identical subject:

super.onResume() at beginning or end of method? Does it matter?

Note the quote from Dianne Hackborn

Yeah this is a good pattern. In most cases it probably doesn't matter, but it's a general rule: during any kind of initialization, let the super class do their work first; during any kind of finalization, you do your work first.

Answer 3

I've never faced any problems calling the super methods before my code and I'm pretty sure I wouldn't have faced any problems if I had called the super methods after my code. But usually super classes instances must be initialized before and deinitialized after subclasses. So ideally you should run your code after calling the super in onCreate(), onStart(), onRestart() and onResume() and before in onPause(), onStop() and onDestroy().

But one more time. All this code is executed on the UI thread so the order of your code doesn't make great sense excluding some rare cases. But the best idea is to read the source code and to understand how it works and what really happens.