出现场景:当点击“分类”再返回“首页”时，发生error退出
BUG描述：Caused by: java.lang.IllegalArgumentException: Binary XML file line #23: Duplicate id 0x7f0d0054, tag null, or parent id 0xffffffff with another fragment for com.example.sxq123.iljmall.FragmentCatagorySpace
//framgment_home.xml
<?xml version="1.0" encoding="utf-8"?>
<LinearLayout xmlns:android="http://schemas.android.com/apk/res/android"
android:orientation="vertical" android:layout_width="match_parent"
android:layout_height="match_parent">
<ScrollView
android:layout_width="fill_parent"
android:layout_height="wrap_content"
android:layout_weight="1">
<LinearLayout
android:orientation="vertical"
android:layout_width="match_parent"
android:layout_height="wrap_content"> <TextView
android:layout_width="wrap_content"
android:layout_height="wrap_content"
android:text = "@string/home"/> <fragment
android:id = "@+id/fragment_space"
android:name = "com.example.sxq123.iljmall.FragmentCatagorySpace"
android:layout_width="match_parent"
android:layout_height="wrap_content"/> </LinearLayout>
</ScrollView>
</LinearLayout>
//FragmentHome.java
public class FragmentHome extends Fragment {
private View view;
FragmentCatagorySpace fragmentCatagorySpace ;
@Override
public View onCreateView(LayoutInflater inflater , ViewGroup container , Bundle savedInsataceState){
view = inflater.inflate(R.layout.fragment_home, null);
Log.d(this.getClass().getName()," onCreateView() Begin");
initChildFragment();
return view;
}
private void initChildFragment(){
Log.d("-------------------","init space ");
fragmentCatagorySpace = (FragmentCatagorySpace)getChildFragmentManager().findFragmentById(R.id.fragment_space);
if(fragmentCatagorySpace != null){
Log.d("----------------","init space success and no null");
}
}
}
问题原因
http://www.tuicool.com/articles/FNVN3i
activity中不同的frament之间项目替换的时候，FragmentManager只会remove和add这些frament，
然而这些frament里面自己加载的frament（这里就是我们的FragmentCatagorySpace）是没有被remove. 很显然这是一个缺陷！
因为后一个frament（FragmentCatagorySpace）很明显是依赖与他的父frament的，应该同时递归的remove.
那么如何解决这个问题呢！很显然就是在不用这个frament（FragmentHome）的时候把他里面加载的frament给remove掉！
这个操作在Fragment的重新onCreateView() inflate layout之前remove掉就可以解决问题了！
比如将remove的事务放在父Fragment的onDestroyView()之中执行
修正后的代码
public class FragmentHome extends Fragment {
private View view;
FragmentCatagorySpace fragmentCatagorySpace ;
@Override
public View onCreateView(LayoutInflater inflater , ViewGroup container , Bundle savedInsataceState){
view = inflater.inflate(R.layout.fragment_home, null);
Log.d(this.getClass().getName()," onCreateView() Begin");
initChildFragment();
return view;
}
@Override
public void onDestroyView(){
super.onDestroyView();
if(fragmentCatagorySpace != null){
Log.d("-------------------", "space no null");
FragmentManager fragmentManager = getFragmentManager();
if(fragmentManager != null && !fragmentManager.isDestroyed()){
final FragmentTransaction fragmentTransaction = fragmentManager.beginTransaction ();
if(fragmentTransaction != null){
fragmentTransaction.remove(fragmentCatagorySpace).commit();
//commit()和commitAllowingStateLoss()都是先发送到主线程任务队列中， 当主线程准备好了再执行，异步。
// //如果没有在inflate之前执行remove child fragmetn 的transaction，将会发生duplicate id 的exception !!!
// fragmentTransaction.commit();//可以放在onCreateView中执行commit()，但偶尔会发生onSaveInstanceState()之后不能执行commit()的冲突
fragmentTransaction.commitAllowingStateLoss();
//立即执行任务队列中的transaction， 不异步 !!!!!!!!!!!!!!!重点!!!!!!!!!!!!!!!!!!!!
//防止remove事务被加到主线程任务队列中，那这样异步的话可能这些事物直到父Fragment重新执行onCreateView()
//之前都没有执行完，同样会发生duplicate id 的异常
//如果这些remove 的食物放在父Fragment的onSaveInstanceState()中执行， 由于onSaveInstanceState()调用并不
//是每一个Fragment生命周期都会被调用(？？？？)，所以偶尔也会发生duplicate id 的异常
fragmentManager.executePendingTransactions();
Log.d("------------------"," space destroy");
}
}
}
}
private void initChildFragment(){
Log.d("-------------------","init space ");
fragmentCatagorySpace = (FragmentCatagorySpace)getChildFragmentManager().findFragmentById(R.id.fragment_space);
if(fragmentCatagorySpace != null){
Log.d("----------------","init space success and no null");
}
}
}
