8

I have a strange problem in which I encountered:The getActivity() method always returns null inside fragment. I calling it after the onAttach() and onCreateView() are finishing their run.

This fragment lives inside a FragmentActivity() that contains stack of fragments, and the way I adding fragment to it is:

(This code is being called from the onCreate() of the Fragment Activity())

SmartFragment fragment;
fragment = (SmartFragment) Fragment.instantiate(this,
fragmentClassName, params);     
mStackOfFragments.add(fragment);
FragmentTransaction trans = getSupportFragmentManager().beginTransaction();
trans.add(R.id.tabcontent, fragment);
trans.addToBackStack(null);
trans.commitAllowingStateLoss();

I hope it is clear enough

Edit 1:

The call to getActivity():

protected OnDoneListener nDoneListener = new OnDoneListener() {

    @Override
    public void OnDone(final int counter, final String name) {


        if (getActivity() != null)
            ((TabActivity) getActivity()).RunOnUiThread(new Runnable() {

... ...

This callback is being called from a different class.

Edit 2:

class MemoryManager()
{

    private OnDoneListener nDoneListener;

    public void setOnDoneListener(OnDoneListener onDoneListener)
    {
    this.onDoneListner = onDoneListener;
    }

    public void updateUiOnRequestFinish()
    {
      onDoneListener.onDone();
    }

}

The MemoryManaget itself calls to updateUiOnRequestFinish() from a different callback

Edit 3:

The FragmentManager logs are:

04-08 18:44:05.950: V/FragmentManager(16280): Commit: BackStackEntry{41f9bd60}
`04-08 18:44:05.950: D/FragmentManager(16280):   mName=null mIndex=-1 mCommitted=false
04-08 18:44:05.950: D/FragmentManager(16280):   Operations:
04-08 18:44:05.950: D/FragmentManager(16280):     Op #0: ADD FragmentMyProfile{41f9bc20 id=0x7f070126}
04-08 18:44:05.950: V/FragmentManager(16280): Setting back stack index 0 to BackStackEntry{41f9bd60}
04-08 18:44:05.950: V/FragmentManager(16280): Run: BackStackEntry{41f9bd60 #0}
04-08 18:44:05.950: V/FragmentManager(16280): Bump nesting in BackStackEntry{41f9bd60 #0} by 1
04-08 18:44:05.950: V/FragmentManager(16280): Bump nesting of FragmentMyProfile{41f9bc20 id=0x7f070126} to 1
04-08 18:44:05.950: V/FragmentManager(16280): add: FragmentMyProfile{41f9bc20 id=0x7f070126}
04-08 18:44:05.950: V/FragmentManager(16280): Allocated fragment index FragmentMyProfile{41f9bc20 #0 id=0x7f070126}
04-08 18:44:05.950: V/FragmentManager(16280): moveto CREATED: FragmentMyProfile{41f9bc20 #0 id=0x7f070126}
04-08 18:44:05.950: V/FragmentManager(16280): moveto ACTIVITY_CREATED: FragmentMyProfile{41f9bc20 #0 id=0x7f070126}
04-08 18:44:05.990: V/FragmentManager(16280): moveto STARTED: FragmentMyProfile{41f9bc20 #0 id=0x7f070126}
04-08 18:44:06.030: V/FragmentManager(16280): moveto RESUMED: FragmentMyProfile{41f9bc20 #0 id=0x7f070126}
`

And it looks fine to me. So I'm guessing that this bug relates to the way I call the getActivity() from the callback.

Sunil Kumar
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Nativ
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    it only strange if you are not familiar with Fragment lifecycle ... http://developer.android.com/guide/components/fragments.html#CoordinatingWithActivity ... also check few lines before this paragraph ... are you adding Fragment to Activity in Activity constuctor? – Selvin Apr 08 '13 at 12:41
  • Can you put the code with the getActivity() line ? – Arnaldo Ignacio Gaspar Véjar Apr 08 '13 at 12:41
  • Selvin: From your comment it implicates that this is a trivial issue, well I hope you are right, but you probably not. I know this link and its content and still having this problem – Nativ Apr 08 '13 at 12:51
  • Did you actually read over the page Selvin linked? _"Caution: If you need a Context object within your Fragment, you can call getActivity(). However, be careful to call getActivity() only when the fragment is attached to an activity. ..."_ I'm not sure what you mean by "after" onAttach and onCreateView, but a fragment is not attached _during_ those methods. Try calling getActivity from onActivityCreated or thereafter. Also, yes, please post where you're actually calling getActivity from. – Charlie Collins Apr 08 '13 at 14:12
  • Ok please see edit 2, the fragment should be attached to activity after the onAttach() onCreateView() and onResume() was called(the fragment is "active" according to the schema in the link). – Nativ Apr 08 '13 at 14:22
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    In cases like this, FragmentManager.enableDebugLogging(true) is a saviour. Look for anything that might be moving your fragment to STOPPED and onwards. Your fragment most certainly is not attached, or getActivity() would be giving you a reference. – Delyan Apr 08 '13 at 14:31

1 Answers1

7

This problem can be for used getActivity() of "android.app.Fragment" or "android.support.v4.app.Fragment"

if your are using "android.support.v4.app.Fragment" you need to review if you aren't using getActivity from "android.app.Fragment" or vice versa.

Maria Mercedes Wyss Alvarez
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  • this solved my problem. i use getSupportActivity() instead of getActivity() as I am using Holo Everywhere. Still don't quite know why getActivity() was working when the fragment first loaded, but not when i would navigate away and then back... – speedynomads Jun 04 '13 at 17:41