Add nullability annotations to ContentSet methods. #650

[lemonboston]

No description provided.

[dmfs]

Please remove mAfterKeys while you're at it. It was only a workaround for the absence of ContentValues.keySet() on Android 2.x. Since we don't support Android 2 any more you can remove it in most places and replace by mAfterContentValues.keySet() where it's being read.

[lemonboston]

Ok, I've removed mAfterKeys.

[dmfs]

I think it doesn't make sense to add a listener for changes to a null key. So key should be @NonNull.

[lemonboston]

There are usages of these methods with null key, so that's why I used Nullable. I've checked now and null actually has a special usage here, see:

opentasks/opentasks/src/main/java/org/dmfs/tasks/model/ContentSet.java

Lines 69 to 73 in 4453861

	/**
	* A {@link Map} for the {@link OnContentChangeListener}s. A listener registers for a specific key in a content set or for <code>null</code> to e notified
	* of full reloads.
	*/
	private final Map<String, Set<OnContentChangeListener>> mOnChangeListeners = new HashMap<String, Set<OnContentChangeListener>>();

So now I've just added some javadoc to the methods about the key parameter.
Let me know if you'd prefer it to be changed somehow.

[dmfs]

I right, I forgot about that. Passing null will cause the listener to be called for any update on any key. Did you check if we actually use that?

[lemonboston]

Yes, they are called with null key from ViewTaskFragment and EditTaskFragment.

[dmfs]

same here, key is @NonNull.