在没有添加到backstack的情况下弹出backstack时找不到id的视图

Question

I am working on an Android app and have encountered an error involving Fragments and FragmentTransactions. I have created an example app to demonstrate the problem. Here is what I am doing:

1. add Fragment1 to fragmentSpace , without adding to backstack.
2. replace fragmentSpace with Fragment2 , adding to backstack as "beginning" .
3. add Fragment3 to fragmentSpace2 (which is inside of Fragment2 ), without adding to backstack.
4. replace fragmentSpace2 with Fragment4 , adding to backstack as null .
5. Call getFragmentManager().popBackStack("beginning", FragmentManager.POP_BACK_STACK_INCLUSIVE); in an attempt to undo all the Transactions, which should bring the user back to seeing only Fragment1 .

However, the app crashes on step 5 with this error:

java.lang.IllegalArgumentException: No view found for id 0x7f090004 (me.MitchT.testfragmenttransactions:id/fragmentSpace2) for fragment Fragment3{7f35cb6 #2 id=0x7f090004}
            at android.app.FragmentManagerImpl.moveToState(FragmentManager.java:886)
            at android.app.FragmentManagerImpl.moveToState(FragmentManager.java:1067)
            at android.app.BackStackRecord.popFromBackStack(BackStackRecord.java:1645)
...

I have found that if I add step 3 to the backstack, step 5 no longer crashes the app and there is no more error. Why?

The problem I have with adding step 3 to the backstack is that I want the user to be able to press the back button after Fragment3 is added and go back to Fragment1 . If I add it to the backstack, then when the user presses the back button it removes Fragment3 , but Fragment2 is still visible, so they must press the back button again . I am trying to avoid that double-back-button behavior.

I did not feel it was necessary to post the code for every single file in the example app on this question, so instead I created a gist.

So I guess my questions are:

1. Why do I get this error?
2. Why don't I get the error after adding step 3 to the backstack?
3. Is there a better way of "going back to the beginning" or going back two fragments at a time?

Thanks!

Answer 1

From what i understand. You have a fragment layout which is the container in activity

Activity hosts Fragment1. Then you replace Fragment 1 by Fragment 2 ( added to back stack.

At this stage clicking back button you will have fragment2 popped and you see the activity which hosts fragment1.

Fragment2 has a framelayout which holds fragment3. Then you have Fragment4 replacing fragment3 which is added to back stack.

Now clicking the button you have getFragmentManager().popBackStack("beginning", FragmentManager.POP_BACK_STACK_INCLUSIVE); . But there is no view with that id.

Just use popBackStack() . Fragment4 --> Fragment2 ( hosting fragment3) --> Fragment1 ( hosted by the activity).

If you want Fragment4 to Activity hosting Fragment1 don't add Fragment4 to the back stack.

Note : In case you want nested fragments you need to use getChildFragmentManager() . https://developer.android.com/about/versions/android-4.2.html

Also note the discussion in the comments sections and the link posted by op Is this the right way to clean-up Fragment back stack when leaving a deeply nested stack?