ListView 滚动的时候更新 ActionBar 的 alpha 值

main.java

mListView.setOnScrollListener(new AbsListView.OnScrollListener() {
        @Override
        public void onScrollStateChanged(AbsListView view, int scrollState) {
        }

        @Override
        public void onScroll(AbsListView view, int firstVisibleItem, int visibleItemCount, int totalItemCount) {
            float ratio = clamp(mHeader.getTranslationY() / mMinHeaderTranslation, 0.0f, 1.0f);
            //actionbar title alpha
            getActionBarTitleView().setAlpha(clamp(5.0F * ratio - 4.0F, 0.0F, 1.0F));
        }
    });
    
public static float clamp(float value, float max, float min) {
    return Math.max(Math.min(value, min), max);
}