动态计算listview的高度listItem.measure(0, 0)报空指针异常解决办法

当我们在使用Listview这类的控件和scrollview嵌套使用的时候会调用一个动态计算listview高度的方法。网上大部分方法基本都如下：

public class Utils {        public static void setListViewHeightBasedOnChildren(ListView listView) {            ListAdapter listAdapter = listView.getAdapter();             if (listAdapter == null) {                // pre-condition                return;            }            int totalHeight = 0;            for (int i = 0; i < listAdapter.getCount(); i++) {                View listItem = listAdapter.getView(i, null, listView);                listItem.measure(0, 0);                totalHeight += listItem.getMeasuredHeight();            }            ViewGroup.LayoutParams params = listView.getLayoutParams();            params.height = totalHeight + (listView.getDividerHeight() * (listAdapter.getCount() - 1));            listView.setLayoutParams(params);        }    }

但是有时候我们会发现每次调用的时候都会产生在listItem.measure(0,0)报空指针异常。但是你去debug会发现listItem 并不是为空，那么为啥会报错呢。你去看你的item的布局会发现肯定不是LinearLayout，这个时候把它换为LinearLayout 就好了。网上的说法是原来是 Linearlayout重写了onmeasure方法，其他的布局文件没有重写onmeasure,所以在调用listItem.measure(0, 0); 会报空指针异常，如果想用这个东东，就必须用linearlayout布局。但是我看源码发现其实并不能这样说，其他布局也是重写了onmeasure方法的，不过谷歌有特别备注说明:

 // We need to know our size for doing the correct computation of children positioning in RTL        // mode but there is no practical way to get it instead of running the code below.        // So, instead of running the code twice, we just set the width to a "default display width"        // before the computation and then, as a last pass, we will update their real position with        // an offset equals to "DEFAULT_WIDTH - width".

大伙去翻译翻译看看啥意思。而且这种情况并不是在所有的手机上会出现，现在很多手机厂商有修改rom。我只是在华为的一款手机上报了这个错。基于这些我写了一个稳妥一点的计算方法：

public class Utils {        public static void setListViewHeightBasedOnChildren(ListView listView) {           ListAdapter listAdapter = listView.getRefreshableView().getAdapter();if (listAdapter == null) {    return;}int totalHeight = 0;for (int i = 0; i < listAdapter.getCount(); i++) {    View listItem = listAdapter.getView(i, null, listView);    if (listItem == null) continue;    if (listItem instanceof LinearLayout){        listItem.measure(0, 0);        totalHeight += listItem.getMeasuredHeight();    }else {        try {            listItem.measure(0, 0);            totalHeight += listItem.getMeasuredHeight();        }catch (NullPointerException e){            totalHeight += DeviceUtil.dp_to_px(ClientApplication.instance,80);//这里自己随便写个大小做容错处理吧            LogOut.e("bobge","NullPointerException");        }    }    totalHeight += listItem.getMeasuredHeight();}ViewGroup.LayoutParams params = listView.getLayoutParams();params.height = totalHeight        + (listView.getRefreshableView().getDividerHeight() * (listAdapter.getCount() - 1));listView.setLayoutParams(params);        }    }