public void setFloatViewManager(FloatViewManager manager) {
        mFloatViewManager = manager;
    }
Called when the float View is dropped; lets you perform
any necessary cleanup. The internal DSLV floating View
reference is set to null immediately after this is called.

@param floatView The floating View passed to
{@link #onCreateFloatView(int)}.
third_party/DragSortListView/src/com/mobeta/android/dslv/DragSortListView.java