In my small Android app, I have a ViewPager
with 3 pages, each page contains one fragment, that's all working fine with a FragmentStatePagerAdapter
(see earlier question).
Now for larger screens, I would like to keep a ViewPager
, but I want the first two fragments to be on the same first page.
For this, I implement my own PagerAdapter and this is mostly working, the only problem I am trying to resolve is when I am rotating the screen, I get an error:
12-11 16:34:13.526: ERROR/AndroidRuntime(9221): FATAL EXCEPTION: main
java.lang.RuntimeException: Unable to start activity ComponentInfo{com.matthieu/com.matthieu.TestActivity}: java.lang.IllegalArgumentException: No view found for id 0x7f030002 (com.matthieu:id/top_fragment) for fragment TestFragment{481a3a98 #0 id=0x7f030002}
at android.app.ActivityThread.performLaunchActivity(ActivityThread.java:2663)
at android.app.ActivityThread.handleLaunchActivity(ActivityThread.java:2679)
at android.app.ActivityThread.handleRelaunchActivity(ActivityThread.java:3815)
at android.app.ActivityThread.access$2400(ActivityThread.java:125)
at android.app.ActivityThread$H.handleMessage(ActivityThread.java:2037)
at android.os.Handler.dispatchMessage(Handler.java:99)
at android.os.Looper.loop(Looper.java:123)
at android.app.ActivityThread.main(ActivityThread.java:4627)
at java.lang.reflect.Method.invokeNative(Native Method)
at java.lang.reflect.Method.invoke(Method.java:521)
at com.android.internal.os.ZygoteInit$MethodAndArgsCaller.run(ZygoteInit.java:871)
at com.android.internal.os.ZygoteInit.main(ZygoteInit.java:629)
at dalvik.system.NativeStart.main(Native Method)
Caused by: java.lang.IllegalArgumentException: No view found for id 0x7f030002 (com.matthieu:id/top_fragment) for fragment TestFragment{481a3a98 #0 id=0x7f030002}
at android.support.v4.app.FragmentManagerImpl.moveToState(FragmentManager.java:903)
at android.support.v4.app.FragmentManagerImpl.moveToState(FragmentManager.java:1088)
at android.support.v4.app.FragmentManagerImpl.moveToState(FragmentManager.java:1070)
at android.support.v4.app.FragmentManagerImpl.dispatchActivityCreated(FragmentManager.java:1861)
at android.support.v4.app.FragmentActivity.onStart(FragmentActivity.java:547)
at android.app.Instrumentation.callActivityOnStart(Instrumentation.java:1129)
at android.app.Activity.performStart(Activity.java:3781)
at android.app.ActivityThread.performLaunchActivity(ActivityThread.java:2636)
... 12 more
I put a sample code simulating what I am trying to do (and showing this error message) on GitHub.
I guess one problem I have is because of the Fragments I have in the real application, I cannot really have a static newInstance
constructor, but instead the Fragments are created ahead of time and have 'setRetainInstance(true);' set.
I understand the id of the viewGroup
that will contain the fragment should be part of the hierarchy, and eventually, I guess, it is...
If it makes any difference, I am using the support library and the SherlockActionBar to maintain backwards compatibility with older devices.
Any idea on how to go about this?
EDIT: I have found that if I remove the Fragments from the FragmentManager
in onSaveInstanceState
I am not getting any crash anymore. All the fragments are recreated from scratch which is not what I want, but I guess I might have to do this and somehow recover those fragments later....
All right, even though I moved to another way of doing things, I don't like to leave things incomplete...
Going the way of the nested Fragments as suggested by Mark. The link posted in the comments goes to 404, but I found your example code about nested fragments.
A few things I've learned on the way:
Nested fragments cannot have setRetainInstance(true)
, or it will get:
java.lang.IllegalStateException: Can't retain fragements that are nested in other fragments
It was a mistake to create a FrameLayout
in the page of the ViewPager
to hold the fragment. Looking in the Android code (and specifically the FragmentPagerAdapter
), I should just use container.getId()
to find where to add the Fragment
. Looks like you cannot do anything more sophisticated at that level or it will break.
From my understanding, if the fragments hold some information (like I do) that takes a long time to load, the different ways to handle this are:
onSaveInstanceState
(preferred way ?), but not possible if the Fragment is nested. The (empty) constructor will get called when needed by the framework.setRetainInstance(true)
, in that case savedInstanceBundle
is always null
, but that Fragment (as Java object) will not be destroyed and it will still go through onAttach / onCreateView.Anyway, I pushed my solution using nested fragments on github
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