Listview item.measure(0, 0);报空指针时问题

最新推荐文章于 2019-09-16 23:48:13 发布

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最新推荐文章于 2019-09-16 23:48:13 发布

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分类专栏： Android 文章标签： listview

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本文解决了一个在Android 4.2及以下版本中ListView截图时出现的空指针异常问题。介绍了错误的原因在于RelativeLayout测量子视图时可能出现的问题，并提供了三种解决方案。

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做了一个截取ListView内容保存为图片的功能，测试的时候发现4.2的模拟器上报错，查看一番之后发现是计算item时候报空指针，查到的解决方案如下：

转载地址：解决方案

当调用listItem.measure(0, 0);报空指针时问题:
检查Adapter适配时Item的根容器为RelativeLayout,
报错原因：
In platform version 17 and lower, RelativeLayout was affected by a measurement bug that could cause child views to be measured with incorrect MeasureSpec values. (See MeasureSpec.makeMeasureSpec for more details.) This was triggered when a RelativeLayout container was placed in a scrolling container, such as a ScrollView or HorizontalScrollView. If a custom view not equipped to properly measure with the MeasureSpec mode UNSPECIFIED was placed in a RelativeLayout, this would silently work anyway as RelativeLayout would pass a very large AT_MOST MeasureSpec instead.
This behavior has been preserved for apps that set android:targetSdkVersion=”17” or older in their manifest’s uses-sdktag for compatibility. Apps targeting SDK version 18 or newer will receive the correct behavior
有三种解决方案：
一、升级版本到4.2.2
二、更改根容器为LinearLayout
三、在适配器里添加convertView.setLayoutParams(new LayoutParams(
LayoutParams.WRAP_CONTENT, LayoutParams.WRAP_CONTENT)); convertView为Item的view