How to use onSaveInstanceState and onRestoreInstanceState

Question

I am trying to save data across orientation changes  As demonstrated in the code below  I use onSaveInstanceState   and onRestoreInstanceState    I try to get the saved value and I check if it is the correct value in onRestoreInstanceState    But when I try to use the new value in onCreate    I don t have the new value but the old one    protected void onSaveInstanceState Bundle outState            super onSaveInstanceState outState           outState putString  TEXT   user          protected void onRestoreInstanceState Bundle savedInstanceState        super onRestoreInstanceState savedInstanceState       savedUser   savedInstanceState getString  TEXT        Log d  enregistred value   savedUser         public void onCreate Bundle savedInstanceState            super onCreate savedInstanceState            int display mode   getResources   getConfiguration   orientation           if  display mode    1                 setContentView R layout main grid               mGrid    GridView  findViewById R id gridview               mGrid setColumnWidth 95               mGrid setVisibility 0x00000000                  mGrid setSystemUiVisibility View SYSTEM UI FLAG LAYOUT HIDE NAVIGATION              else               setContentView R layout main grid land               mGrid    GridView  findViewById R id gridview               mGrid setColumnWidth 95               Log d  Mode    land                   mGrid setSystemUiVisibility View SYSTEM UI FLAG LAYOUT HIDE NAVIGATION                      Log d  savedUser   savedUser           if  savedUser equals  admin        value 0             adapter setApps appManager getApplications               else if  savedUser equals  prof        value 1             adapter setApps appManager getTeacherApplications               else     default value             appManager   new ApplicationManager this  getPackageManager                 appManager loadApplications true               bindApplications

User · Answer

This happens because you use the savedValue in the onCreate   method  The savedValue is updated in onRestoreInstanceState   method  but onRestoreInstanceState   is called after the onCreate   method  You can either    Update the savedValue in onCreate   method  or Move the code that use the new savedValue in onRestoreInstanceState   method    But I suggest you to use the first approach  making the code like this   public void onCreate Bundle savedInstanceState        super onCreate savedInstanceState        int display mode   getResources   getConfiguration   orientation       if  display mode    1             setContentView R layout main grid           mGrid    GridView  findViewById R id gridview           mGrid setColumnWidth 95           mGrid setVisibility 0x00000000              mGrid setSystemUiVisibility View SYSTEM UI FLAG LAYOUT HIDE NAVIGATION          else           setContentView R layout main grid land           mGrid    GridView  findViewById R id gridview           mGrid setColumnWidth 95           Log d  Mode    land               mGrid setSystemUiVisibility View SYSTEM UI FLAG LAYOUT HIDE NAVIGATION              if  savedInstanceState    null            savedUser   savedInstanceState getString  TEXT          else           savedUser                Log d  savedUser   savedUser       if  savedUser equals  admin        value 0         adapter setApps appManager getApplications           else if  savedUser equals  prof        value 1         adapter setApps appManager getTeacherApplications           else     default value         appManager   new ApplicationManager this  getPackageManager             appManager loadApplications true           bindApplications

User · Answer

onSaveInstanceState   is a method used to store data before pausing the activity    Description   Hook allowing a view to generate a representation of its internal state that can later be used to create a new instance with that same state  This state should only contain information that is not persistent or can not be reconstructed later  For example  you will never store your current position on screen because that will be computed again when a new instance of the view is placed in its view hierarchy     onRestoreInstanceState   is method used to retrieve that data back    Description   This method is called after onStart   when the activity is being re-initialized from a previously saved state  given here in savedInstanceState  Most implementations will simply use onCreate Bundle  to restore their state  but it is sometimes convenient to do it here after all of the initialization has been done or to allow subclasses to decide whether to use your default implementation  The default implementation of this method performs a restore of any view state that had previously been frozen by onSaveInstanceState Bundle     Consider this example here  You app has 3 edit boxes where user was putting in some info   but he gets a call so if you didn t use the above methods what all he entered will be lost  So always save the current data in onPause   method of Activity as a bundle  amp  in onResume   method call the onRestoreInstanceState   method    Please see    How to use onSavedInstanceState example please  http   www how-to-develop-android-apps com tag onrestoreinstancestate

User · Answer

When your activity is recreated after it was previously destroyed  you   can recover your saved state from the Bundle that the system passes   your activity  Both the onCreate   and onRestoreInstanceState     callback methods receive the same Bundle that contains the instance   state information       Because the onCreate   method is called whether the system is creating   a new instance of your activity or recreating a previous one  you must   check whether the state Bundle is null before you attempt to read it    If it is null  then the system is creating a new instance of the   activity  instead of restoring a previous one that was destroyed    static final String STATE USER    user   private String mUser    Override protected void onCreate Bundle savedInstanceState        super onCreate savedInstanceState          Check whether we re recreating a previously destroyed instance     if  savedInstanceState    null               Restore value of members from saved state         mUser   savedInstanceState getString STATE USER         else              Probably initialize members with default values for a new instance         mUser    NewUser             Override public void onSaveInstanceState Bundle savedInstanceState        savedInstanceState putString STATE USER  mUser          Always call the superclass so it can save the view hierarchy state     super onSaveInstanceState savedInstanceState       http   developer android com training basics activity-lifecycle recreating html

[android] How to use onSaveInstanceState() and onRestoreInstanceState()?

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