public boolean setItem(final int item, final OnPageChangeListener listener) {
        final boolean changed = setItem(item);
        if (changed && listener != null) {
            listener.onPageSelected(item);
        }
        return changed;
    }
Set current item, invoke the listener if changes, and return whether the
item changed
<p>
This method does not call {@link #setCurrentItem(int)} unless the item
parameter differs from the current item

@param item
@param listener
@return true if set, false if same
app/src/main/java/com/github/pockethub/android/ui/ViewPager.java