FragmentPagerAdapter Bug(Android NullPointerException FragmentHostCallback.getHandler())

在用到FragmentPagerAdapter的时候，出现了下面的错误：

java.lang.NullPointerException: Attempt to invoke virtual method 'android.os.Handler android.support.v4.app.FragmentHostCallback.getHandler()' on a null object reference

看到这个，瞬间懵逼了，于是在网上怒搜，没想到，好多人都碰到了这个问题，原来这个是Google support library的问题，而且一直没有解决：

#3 nksa...@gmail.com  
This is also bug too on 24.1.1  
  
Aug 3, 2016#4 rfml...@gmail.com  
Any workaround anyone?  
  
Aug 6, 2016#5 chernand...@gmail.com  
I am having the same error  
Nexus 5, android 6.0.1, support library 24.0.0.  
  
Aug 11, 2016#6 christi...@carezone.com  
Probably related to https://code.google.com/p/android/issues/detail?id=208911  
  
Aug 12, 2016#7 ffvander...@gmail.com  
and to https://code.google.com/p/android/issues/detail?can=2&start=0&num=100&q=&colspec=ID%20Status%20Priority%20Owner%20Summary%20Stars%20Reporter%20Opened&groupby=&sort=&id=218912  
  
Aug 12, 2016Project Member #8 amruthav...@google.com  
(No comment was entered for this change.)  
Status: Duplicate   
Owner: amruthav...@google.com   
Mergedinto: 218912   
  
Aug 18, 2016#9 fernando...@gmail.com  
Still around in 'com.android.support:support-v4:24.2.0'  
Does anyone has any workaround for this?  
  
Thanks!  
  
Aug 22, 2016#10 meghal.s...@teamaol.com  
This story has been merged into https://code.google.com/p/android/issues/detail?id=218912  
  
Sep 26, 2016#12 rfml...@gmail.com  
Still around in 'com.android.support:support-v4:24.2.1'  
  
Does anyone got any workaround for this?

可以看出，各种人吐槽，而且google一直没有修复，也没有打算修复的想法，最后一个人直接这样质问Google的开发者，也是够直接，够犀利：

#14 nksa...@gmail.com  
Googlers it is shame that the bug is there in view pager more than 3 years.  Why don't you take seriously? Fix it guys can't wait more time

没办法，我也是各种搜索，最后总算找到了一种解决办法，但是具体出处忘了,这里感谢一下！
在你的FragmentPagerAdapter代码下，复写finishUpdate方法：

@Override  
public void finishUpdate(ViewGroup container) {  
     try{  
         super.finishUpdate(container);  
     } catch (NullPointerException nullPointerException){  
         Log.d("Catch the NullPointerException in FragmentPagerAdapter.finishUpdate");  
     }  
} 

当然，因为我是在异步线程之后调用notifyDataSetChanged刷新adapter的，所以也可以在刷新之前判断viewpager的状态：

if (viewPager == null || isDetached()) return;