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：
[java] view plain copy
1. public class Utils {
2. public static void setListViewHeightBasedOnChildren(ListView listView) {
3. ListAdapter listAdapter = listView.getAdapter();
4. if (listAdapter == null) {
5. // pre-condition
6. return;
7. }
8.
9. int totalHeight = 0;
10. for (int i = 0; i < listAdapter.getCount(); i++) {
11. null, listView);
12. 0, 0);
13. totalHeight += listItem.getMeasuredHeight();
14. }
15.
16. ViewGroup.LayoutParams params = listView.getLayoutParams();
17. 1));
18. listView.setLayoutParams(params);
19. }
20. }
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:
[java] view plain copy
1. // We need to know our size for doing the correct computation of children positioning in RTL
2. // mode but there is no practical way to get it instead of running the code below.
3. // So, instead of running the code twice, we just set the width to a "default display width"
4. // before the computation and then, as a last pass, we will update their real position with
5. // 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：
[java] view plain copy
1. public class Utils {
2. public static void setListViewHeightBasedOnChildren(ListView listView) {
3.
4. ListAdapter listAdapter = listView.getRefreshableView().getAdapter();
5. if (listAdapter == null) {
6. return;
7. }
8.
9. int totalHeight = 0;
10.
11. for (int i = 0; i < listAdapter.getCount(); i++) {
12.
13. null, listView);
14. if (listItem == null) continue;
15.
16. if (listItem instanceof LinearLayout){
17. 0, 0);
18. totalHeight += listItem.getMeasuredHeight();
19. else {
20. try {
21. 0, 0);
22. totalHeight += listItem.getMeasuredHeight();
23. catch (NullPointerException e){
24. 80);//这里自己随便写个大小做容错处理吧
25. "bobge","NullPointerException");
26. }
27. }
28.
29. totalHeight += listItem.getMeasuredHeight();
30.
31. }
32.
33. ViewGroup.LayoutParams params = listView.getLayoutParams();
34.
35. params.height = totalHeight
36. 1));
37.
38.
39. listView.setLayoutParams(params);
40.
41. }
42. }
