两种Android判断view是否部分被遮挡（或者移出屏幕）的方法

最新推荐文章于 2024-07-31 16:31:01 发布

unicorn97

最新推荐文章于 2024-07-31 16:31:01 发布

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分类专栏： android基础文章标签： android listview headerView滑动判断

本文链接：https://blog.youkuaiyun.com/unicorn97/article/details/50818228

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部分内容参考http://blog.youkuaiyun.com/peidonghui/article/details/49583263，在此对原作者表示感谢。

在某些需求下，需要判断某一个View是否被遮挡，比如ListView的headerView中某一个View在ListView向上滑动到开始不可见时，在页面顶部固定显示一个View。在刚开始时，处理方式是在ListView的onScroll（）中判断该View距离屏幕顶部的距离，来作为判断条件，网上好不容易找到解决方法，但测试的妹纸却在android 6.0的手机上测出兼容性BUG ，害得我周末跟妹纸约会都在想这个问题该怎么办，看来还是要仔细系统的研究一下自定义View和ViewGroup的相关问题

废话不多说，直接上代码。

1.当Android 的版本为6.0以下时

</pre><pre name="code" class="java">

</pre><pre name="code" class="java">

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


            }


            @Override
            public void onScroll(AbsListView view, int firstVisibleItem, int visibleItemCount, int totalItemCount) {
                Rect rect = new Rect();
                line.getGlobalVisibleRect(rect);
                if ((rect.top < statusBarHeight + DimenUtil.dip2px(mContext, 97)) ) {
                    if (rl_choosed_tag.getVisibility() == View.INVISIBLE)
                        rl_choosed_tag.setVisibility(View.VISIBLE);
                } else {
                    if (rl_choosed_tag.getVisibility() == View.VISIBLE)
                        rl_choosed_tag.setVisibility(View.INVISIBLE);
                }
            }
        });

以上line为listView的headerView布局中的一个view，通过line.getGlobalVisibleRect(rect);来判断该view距离屏幕顶部的距离是否小于指定值（此处该临界值为

statusBarHeight + DimenUtil.dip2px(mContext, 97)）来作为另外一个View是否显示的条件

2.当Android 的S版本为6.0时

在onScroll()中这样处理

if (Build.VERSION.SDK_INT >= 23) {
    if (isViewCovered(mSortFlowLayout)) {
        if (rl_choosed_tag.getVisibility() == View.VISIBLE)
            rl_choosed_tag.setVisibility(View.INVISIBLE);
    } else {
        if (rl_choosed_tag.getVisibility() == View.INVISIBLE)
            rl_choosed_tag.setVisibility(View.VISIBLE);
    }
}

涉及的isViewCovered()函数如下：

public boolean isViewCovered(final View view) {
    View currentView = view;

    Rect currentViewRect = new Rect();
    boolean partVisible = currentView.getGlobalVisibleRect(currentViewRect);
    boolean totalHeightVisible = (currentViewRect.bottom - currentViewRect.top) >= view.getMeasuredHeight();
    boolean totalWidthVisible = (currentViewRect.right - currentViewRect.left) >= view.getMeasuredWidth();
    boolean totalViewVisible = partVisible && totalHeightVisible && totalWidthVisible;
    if (!totalViewVisible)//if any part of the view is clipped by any of its parents,return true
        return true;

    while (currentView.getParent() instanceof ViewGroup) {
        ViewGroup currentParent = (ViewGroup) currentView.getParent();
        if (currentParent.getVisibility() != View.VISIBLE)//if the parent of view is not visible,return true
            return true;

        int start = indexOfViewInParent(currentView, currentParent);
        for (int i = start + 1; i < currentParent.getChildCount(); i++) {
            Rect viewRect = new Rect();
            view.getGlobalVisibleRect(viewRect);
            View otherView = currentParent.getChildAt(i);
            Rect otherViewRect = new Rect();
            otherView.getGlobalVisibleRect(otherViewRect);
            if (Rect.intersects(viewRect, otherViewRect))//if view intersects its older brother(covered),return true
                return true;
        }
        currentView = currentParent;
    }
    return false;
}


private int indexOfViewInParent(View view, ViewGroup parent) {
    int index;
    for (index = 0; index < parent.getChildCount(); index++) {
        if (parent.getChildAt(index) == view)
            break;
    }
    return index;
}

虽然一个简单的判断却还需要分版本不同单独处理，不过应该有更加简洁优雅的解决方案，欢迎各位给出指导。