popBackStack causes calling oncreateView of fragment again and again

问题

I have 3 fragment A, B,C.I wrote piece of code for replacing them and maintaining backstack:

 public void addFragment(Fragment fragmentToAdd, String fragmentTag) {
        FragmentManager supportFragmentManager = getSupportFragmentManager();
        Fragment activeFragment = getActiveFragment();
        FragmentTransaction fragmentTransaction = supportFragmentManager
                .beginTransaction();
        if (null != activeFragment) {
            fragmentTransaction.hide(activeFragment);
        }
        fragmentTransaction.replace(R.id.layout_child_activity, fragmentToAdd,
                fragmentTag);

       if (supportFragmentManager.getBackStackEntryCount() > 1) {
            supportFragmentManager.popBackStack();
        }
        fragmentTransaction.addToBackStack(fragmentTag);
        fragmentTransaction.commit();
    }

Here in this piece of code

if (supportFragmentManager.getBackStackEntryCount() > 1) {
    supportFragmentManager.popBackStack();
}

I using for pop the latest fragment if stack length is more than 1. Now due to this when length is going greater than 1 than it is calling onCreate view again and again. Like :

1. open A.
2. open B.
3. open C.(In case of open C. onCreateView of A is called. )

Why I am getting such kind of behavior ? When I am removing that italic code than it is not happening.

回答1:

Than behavior is normal, coming from the backstack transaction, as the docs say. The backstack never saves Fragments, it just saves the transaction

http://developer.android.com/intl/es/guide/components/fragments.html

What I do, I am not sure if, is it the best way but when I want to clear all the transactions I do this

1) INSIDE YOUR ACTIVITY check if is there any transactions in the back stack, and add a flag inside your fragment, in your case is A

       int backStackCount = getSupportFragmentManager().getBackStackEntryCount();

       if(backStackCount > 0) {
           Transactions.MUST_DETACH_FROM_BACKSTACK = true;
           getSupportFragmentManager().popBackStackImmediate(null, FragmentManager.POP_BACK_STACK_INCLUSIVE);
       }

2) Inside your fragment A, get the flag and Remove the fragment onCreateView and return null like this

public class Transactions extends android.support.v4.app.Fragment{

public static boolean MUST_DETACH_FROM_BACKSTACK = false;

public Transactions() {
    // Required empty public constructor
}


@Override
public View onCreateView(LayoutInflater inflater, ViewGroup container,
                         Bundle savedInstanceState) {
    Log.i("FRAGMENT", "onCreateView "+MUST_DETACH_FROM_BACKSTACK);
    // Inflate the layout for this fragment
    if (MUST_DETACH_FROM_BACKSTACK) {
        MUST_DETACH_FROM_BACKSTACK = false;
        getActivity().getSupportFragmentManager().beginTransaction().remove(this).commit();
        return null;
    }
    return inflater.inflate(R.layout.fragment_transactions, container, false);
}

@Override
public void onViewCreated(View view, Bundle savedInstanceState) {
    super.onViewCreated(view, savedInstanceState);


    Log.i("FRAGMENT", "onViewCreated");
    if(view != null){

        Log.i("FRAGMENT", "ThreadStarted");
        startThread(view);
    }
}

BUT BE CAREFULL I Get onResume() Called after the

OnCreateView()

even with getActivity().getSupportFragmentManager().beginTransaction().remove(this).commit();

So if you have any conde onResume method you should handle it properly

回答2:

I solved this problem by inheriting (1) all fragments from my custom BaseFragment (2). In this BaseFragment I created a variable: public static boolean removing; (3) and set it to true (4) before calling popBackStackImmediate() and reset it to false after that. (5) In the BaseFragment-childs I check the variable. (6)

Example-Code

Activity-class

    BaseFragment.removing = true; //(4)
    //pop all fragments
    while(getSupportFragmentManager().getBackStackEntryCount() > 0){
        fragmentManager.popBackStackImmediate();
    }
    BaseFragment.removing = false; //(5)

BaseFragment (2)

public class BaseFragment extends Fragment{
   public static boolean removing = false; //(3)
}

Fragment-Child

public class fragment extends BaseFragment{ //(1)
  @Override
  public void onViewCreated(View view, @Nullable Bundle savedInstanceState) {
      if(!removing){ // (6)
          //your code
      }
  }
}

来源：https://stackoverflow.com/questions/22278602/popbackstack-causes-calling-oncreateview-of-fragment-again-and-again