Question

What does the method adapter.notifyDataSetInvalidated() accomplish?
There is no documentation on it.

I am trying to reload a ListView and notifyDataSetChanged or notifyDataSetInvalidated don’t seem to accomplish anything.

Answer 1

It depends on the adapter implementation… if you take a look of the source code you will see that:

1. notifyDataSetInvalidated() calls the notifyInvalidated() of the DataSetObservable class (see here)
2. Then, notifyInvalidated() calls the onInvalidated() method for each DataSetObserver (see here).
3. Then comes the funny part: onInvalidated() does not do anything…

This is its implementation:

public void onInvalidated() {
    // Do nothing
}

DataSetObserver is an abstract class, so it’s up to the subclass to decide what to do on onInvalidated().