ListViewにonScrollListenerをaddする

addOnScrollListener.java

// リフレクション使ってもともとsetしてあるonScrollのlistenerを取ってくる
AbsListView listView = (AbsListView) mParentScrollableView;
AbsListView.OnScrollListener onScrollListener = null;
Class<?> listViewClass = mParentScrollableView.getClass();
try {
    while (listViewClass != AbsListView.class) {
        listViewClass = listViewClass.getSuperclass();
    }
    // field名は決め打ち
    Field field = listViewClass.getDeclaredField("mOnScrollListener");
    field.setAccessible(true);
    onScrollListener = (AbsListView.OnScrollListener) field.get(listView);
} catch (NoSuchFieldException e) {
    e.printStackTrace();
} catch (IllegalAccessException e) {
    e.printStackTrace();
}

final AbsListView.OnScrollListener defaultOnScrollListener = onScrollListener;

listView.setOnScrollListener(new AbsListView.OnScrollListener() {
    @Override
    public void onScrollStateChanged(AbsListView view, int scrollState) {
        if (defaultOnScrollListener != null) {
            defaultOnScrollListener.onScrollStateChanged(view, scrollState);
        }
    }
    @Override
    public void onScroll(AbsListView absListView, int firstVisibleItem, int visibleItemCount, int totalItemCount) {
        if (defaultOnScrollListener != null) {
            defaultOnScrollListener.onScroll(absListView, firstVisibleItem, visibleItemCount, totalItemCount);
        }
        // do something
    }
});