Fragment MyFragment not attached to Activity

Question

I ve created a small test app which represents my problem  I m using ActionBarSherlock to implement tabs with  Sherlock Fragments   My code  TestActivity java  public class TestActivity extends SherlockFragmentActivity       private ActionBar actionBar        Override     public void onCreate Bundle savedInstanceState            super onCreate savedInstanceState           setupTabs savedInstanceState              private void setupTabs Bundle savedInstanceState            actionBar   getSupportActionBar            actionBar setNavigationMode ActionBar NAVIGATION MODE TABS            addTab1            addTab2               private void addTab1             Tab tab1   actionBar newTab            tab1 setTag  1            String tabText    1           tab1 setText tabText           tab1 setTabListener new TabListener lt MyFragment gt  TestActivity this   1   MyFragment class             actionBar addTab tab1              private void addTab2             Tab tab1   actionBar newTab            tab1 setTag  2            String tabText    2           tab1 setText tabText           tab1 setTabListener new TabListener lt MyFragment gt  TestActivity this   2   MyFragment class             actionBar addTab tab1             TabListener java  public class TabListener lt T extends SherlockFragment gt  implements com actionbarsherlock app ActionBar TabListener       private final SherlockFragmentActivity mActivity      private final String mTag      private final Class lt T gt  mClass       public TabListener SherlockFragmentActivity activity  String tag  Class lt T gt  clz            mActivity   activity          mTag   tag          mClass   clz                The following are each of the ActionBar TabListener callbacks         public void onTabSelected Tab tab  FragmentTransaction ft            SherlockFragment preInitializedFragment    SherlockFragment  mActivity getSupportFragmentManager   findFragmentByTag mTag               Check if the fragment is already initialized         if  preInitializedFragment    null                   If not  instantiate and add it to the activity             SherlockFragment mFragment    SherlockFragment  SherlockFragment instantiate mActivity  mClass getName                 ft add android R id content  mFragment  mTag             else               ft attach preInitializedFragment                        public void onTabUnselected Tab tab  FragmentTransaction ft            SherlockFragment preInitializedFragment    SherlockFragment  mActivity getSupportFragmentManager   findFragmentByTag mTag            if  preInitializedFragment    null                   Detach the fragment  because another one is being attached             ft detach preInitializedFragment                        public void onTabReselected Tab tab  FragmentTransaction ft               User selected the already selected tab  Usually do nothing            MyFragment java  public class MyFragment extends SherlockFragment         Override     public void onCreate Bundle savedInstanceState            super onCreate savedInstanceState            new AsyncTask lt Void  Void  Void gt                    Override             protected Void doInBackground Void    params                    try                       Thread sleep 2000                     catch  InterruptedException ex                                      return null                              Override             protected void onPostExecute Void result                   getResources   getString R string app name                            execute              I ve added the Thread sleep part to simulate downloading data  The code in the onPostExecute is to simulate use of the Fragment   When I rotate the screen very fast between landscape and portrait  I get an Exception at the onPostExecute code       java lang IllegalStateException  Fragment MyFragment 410f6060  not   attached to Activity   I think it s because a new MyFragment has been created in the meantime  and was attached to the Activity before the AsyncTask finished  The code in onPostExecute calls upon a unattached MyFragment   But how can I fix this

User · Accepted Answer

I ve found the very simple answer  isAdded        Return true if the fragment is currently added to its activity     Override protected void onPostExecute Void result       if isAdded             getResources   getString R string app name             To avoid onPostExecute from being called when the Fragment is not attached to the Activity is to cancel the AsyncTask when pausing or stopping the Fragment  Then isAdded   would not be necessary anymore  However  it is advisable to keep this check in place

User · Answer

I ve faced two different scenarios here   1  When I want the asynchronous task to finish anyway  imagine my onPostExecute does store data received and then call a listener to update views so  to be more efficient  I want the task to finish anyway so I have the data ready when user cames back  In this case I usually do this    Override protected void onPostExecute void result           do whatever you do to save data     if  this getView      null               update views           2  When I want the asynchronous task only to finish when views can be updated  the case you re proposing here  the task only updates the views  no data storage needed  so it has no clue for the task to finish if views are not longer being showed  I do this    Override protected void onStop            notice here that I keep a reference to the task being executed as a class member      if  this myTask    null  amp  amp  this myTask getStatus      Status RUNNING  this myTask cancel true       super onStop        I ve found no problem with this  although I also use a  maybe  more complex way that includes launching tasks from the activity instead of the fragments   Wish this helps someone

User · Answer

simple solution and work 100  if  getActivity      null     isAdded    return

User · Answer

I faced similar issues when the application settings activity with the loaded preferences was visible  If I would change one of the preferences and then make the display content rotate and change the preference again  it would crash with a message that the fragment  my Preferences class  was not attached to an activity   When debugging it looked like the onCreate   Method of the PreferencesFragment was being called twice when the display content rotated  That was strange enough already  Then I added the isAdded   check outside of the block where it would indicate the crash and it solved the issue   Here is the code of the listener that updates the preferences summary to show the new entry  It is located in the onCreate   method of my Preferences class which extends the PreferenceFragment class   public static class Preferences extends PreferenceFragment       SharedPreferences OnSharedPreferenceChangeListener listener        Override     public void onCreate Bundle savedInstanceState                           listener   new SharedPreferences OnSharedPreferenceChangeListener                  Override             public void onSharedPreferenceChanged SharedPreferences sharedPreferences  String key                       check if the fragment has been added to the activity yet  necessary to avoid crashes                  if  isAdded                             for the preferences of type  list  set the summary to be the entry of the selected item                     if  key equals getString R string pref fileviewer textsize                              ListPreference listPref    ListPreference  findPreference key                           listPref setSummary  Display file content with a text size of     listPref getEntry                           else if  key equals getString R string pref fileviewer segmentsize                              ListPreference listPref    ListPreference  findPreference key                           listPref setSummary  Show     listPref getEntry       bytes of a file at once                                                                                            I hope this will help others

User · Answer

An old post  but I was surprised about the most up-voted answer   The proper solution for this should be to cancel the asynctask in onStop  or wherever appropriate in your fragment   This way you don t introduce a memory leak  an asynctask keeping a reference to your destroyed fragment  and you have better control of what is going on in your fragment    Override public void onStop         super onStop        mYourAsyncTask cancel true

User · Answer

I faced the same problem i just add the singletone instance to get resource as referred by Erick   MainFragmentActivity defaultInstance   getResources   getString R string app name     you can also use   getActivity   getResources   getString R string app name     I hope this will help

User · Answer

If you extend the Application class and maintain a static  global  Context object  as follows  then you can use that instead of the activity to load a String resource   public class MyApplication extends Application       public static Context GLOBAL APP CONTEXT        Override     public void onCreate             super onCreate            GLOBAL APP CONTEXT   this            If you use this  you can get away with Toast and resource loading without worrying about lifecycles

User · Answer

if  getActivity      null  return    works also in some cases  Just breaks the code execution from it and make sure the app not crash

User · Answer

The problem is that you are trying to access resources  in this case  strings  using getResources   getString    which will try to get the resources from the Activity  See this source code of the Fragment class            Return  lt code gt getActivity   getResources   lt  code gt         final public Resources getResources          if  mHost    null             throw new IllegalStateException  Fragment     this     not attached to Activity                return mHost getContext   getResources         mHost is the object that holds your Activity   Because the Activity might not be attached  your getResources   call will throw an Exception   The accepted solution IMHO is not the way to go as you are just hiding the problem  The correct way is just to get the resources from somewhere else that is always guaranteed to exist  like the application context   youApplicationObject getResources   getString

User · Answer

Their are quite trick solution for this and leak of fragment from activity   So in case of getResource or anything one which is depending on activity context accessing from Fragment it is always check activity status and fragments status as follows    Activity activity   getActivity         if activity    null  amp  amp  isAdded              getResources   getString R string no internet error msg     Or any other depends on activity context to be live like dailog

User · Answer

I had a similar error message  quot Fragment MyFragment not attached to Context quot  in Xamarine Android  this error messege getting because of this resource calling button Text   Resources GetString Resource String please wait   I did fix that by using in Xamarine Android  if  Context    null  amp  amp  IsAdded        button Text   Resources GetString Resource String please wait

User · Answer

The problem with your code is the way the you are using the AsyncTask  because when you rotate the screen during your sleep thread    Thread sleep 2000     the AsyncTask is still working  it is because you didn t cancel the AsyncTask instance properly in onDestroy   before the fragment rebuilds  when you rotate  and when this same AsyncTask instance  after rotate  runs onPostExecute    this tries to find the resources with getResources   with the old fragment instance an invalid instance     getResources   getString R string app name    which is equivalent to   MyFragment this getResources   getString R string app name    So the final solution is manage the AsyncTask instance  to cancel if this is still working  before the fragment rebuilds when you rotate the screen  and if canceled during the transition  restart the AsyncTask after reconstruction by the aid of a boolean flag   public class MyFragment extends SherlockFragment        private MyAsyncTask myAsyncTask   null      private boolean myAsyncTaskIsRunning   true        Override     public void onCreate Bundle savedInstanceState            super onCreate savedInstanceState           if savedInstanceState  null                myAsyncTaskIsRunning   savedInstanceState getBoolean  myAsyncTaskIsRunning                      if myAsyncTaskIsRunning                myAsyncTask   new MyAsyncTask                myAsyncTask execute                          Override     public void onSaveInstanceState Bundle outState            super onSaveInstanceState outState           outState putBoolean  myAsyncTaskIsRunning  myAsyncTaskIsRunning               Override     public void onDestroy             super onDestroy            if myAsyncTask  null  myAsyncTask cancel true           myAsyncTask   null              public class MyAsyncTask extends AsyncTask lt Void  Void  Void gt               public MyAsyncTask               Override         protected void onPreExecute                 super onPreExecute                myAsyncTaskIsRunning   true                     Override         protected Void doInBackground Void    params                try                   Thread sleep 2000                 catch  InterruptedException ex                 return null                      Override         protected void onPostExecute Void result               getResources   getString R string app name               myAsyncTaskIsRunning   false              myAsyncTask   null

User · Answer

In my case fragment methods have been called after  getActivity   onBackPressed

[android] Fragment MyFragment not attached to Activity

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