How do I programmatically restart an Android app

Question

Firstly  I know that one should not really kill restart an application on Android  In my use case  I want to factory-reset my application in a specific case where a server sends a piece of specific information to the client  The user can only be logged in on the server with ONE instance of the application  i e  multiple devices are not allowed   If another instance gets that  quot logged-in quot -lock then all other instances of that user have to delete their data  factory-reset   to maintain consistency  It is possible to forcibly get the lock because the user might delete the app and reinstall it which would result in a different instance-id and the user would not be able to free the lock anymore  Therefore it is possible to forcibly get the lock  Because of that force-possibility  we need to always check in a concrete instance that it has the lock  That is done on  almost  each request to the server  The server might send a  quot wrong-lock-id quot   If that is detected  the client application must delete everything   That was the use-case  I have an Activity A that starts the Login Activity L or the app s main Activity B depending on a sharedPrefs value  After starting L or B it closes itself so that only L or B is running  So in the case that the user is logged in already B is running now  B starts C  C calls startService for the IntentService D  That results in this stack   A   gt  B  gt  C  gt  D From the onHandleIntent method of D  an event is sent to a ResultReceiver R  R now handles that event by providing the user a dialog where he can choose to factory-reset the application  delete the database  sharedPrefs  etc   After the factory-reset I want to restart the application  to close all activities  and only start A again which then launches the login Activity L and finishes itself   A   gt  L The Dialog s onClick-method looks like this   Override public void onClick DialogInterface dialog  int which            Will call onCancelListener     MyApplication factoryReset        Deletes the database  clears sharedPrefs  etc       Intent i   new Intent MyApp getContext    A class       i setFlags Intent FLAG ACTIVITY CLEAR TOP       i addFlags Intent FLAG ACTIVITY NEW TASK       MyApp getContext   startActivity i      And that s the MyApp class  public class MyApp extends Application       private static Context context        Override     public void onCreate             super onCreate            context   getApplicationContext               public static Context getContext             return context             public static void factoryReset                             The problem is if I use the FLAG ACTIVITY NEW TASK the Activities B and C are still running  If I hit the back button on the login Activity I see C  but I want to go back to the home screen  If I do not set the FLAG ACTIVITY NEW TASK I get the error  07-07 12 27 12 272  ERROR AndroidRuntime 9512   android util AndroidRuntimeException  Calling startActivity   from outside of an Activity  context requires the FLAG ACTIVITY NEW TASK flag  Is this really what you want   I cannot use the Activities  Context  because the ServiceIntent D might also be called from a background task which is started by the AlarmManager  So how could I solve this to the activity stack becoming  A   gt  L

User · Answer

Kotlin version of this answer  val intent   Intent this  YourActivity  class java  intent addFlags Intent FLAG ACTIVITY CLEAR TASK or Intent FLAG ACTIVITY CLEAR TASK  startActivity intent  Runtime getRuntime   exit 0

User · Answer

You can use startInstrumentation method of Activity  You need implement empty Instrumentation and pointed in manifest  After that you can call this method for restart your app  Like this   try                  InstrumentationInfo info   getPackageManager   queryInstrumentation getPackageName    0  get 0       ComponentName component   new ComponentName this  Class forName info name        startInstrumentation component  null  null     catch  Throwable e                     new RuntimeException  Failed restart with Instrumentation   e       I get Instrumentation class name dynamically but you can hardcode it  Some like this   try                  startInstrumentation new ComponentName this  RebootInstrumentation class   null  null      catch  Throwable e                     new RuntimeException  Failed restart with Instrumentation   e       Call startInstrumentation make reload of your app  Read description of this method  But it can be not safe if acting like kill app

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Intent i   getBaseContext   getPackageManager   getLaunchIntentForPackage  getBaseContext   getPackageName      i addFlags Intent FLAG ACTIVITY CLEAR TOP   startActivity i

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Mikepenz s Alternative Answer needed some changes in my case  https   stackoverflow com a 22345538 12021422 Major Credits to Mikepenz s Answer which I could modify  Here is the Plug and Play static function that worked for me  Just pass the Context of Application and this function will handle the restart      public static void doRestart Context c            try                  check if the context is given             if  c    null                       fetch the package manager so we can get the default launch activity                     you can replace this intent with any other activity if you want                 PackageManager pm   c getPackageManager                       check if we got the PackageManager                 if  pm    null                           create the intent with the default start activity for your application                     Intent mStartActivity   pm getLaunchIntentForPackage c getPackageName                         if  mStartActivity    null                            mStartActivity addFlags Intent FLAG ACTIVITY CLEAR TOP                                                    c getApplicationContext   startActivity mStartActivity                              kill the application                         System exit 0                                                                   catch  Exception e                e printStackTrace                Log e  quot restart quot    quot Could not Restart quot

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My solution doesn t restart the process application  It only lets the app  restart  the home activity  and dismiss all other activities   It looks like a restart to users  but the process is the same  I think in some cases people want to achieve this effect  so I just leave it here FYI   public void restart        Intent intent   new Intent this  YourHomeActivity class       this startActivity intent       this finishAffinity

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You can use PendingIntent to setup launching your start activity in the future and then close your application  Intent mStartActivity   new Intent context  StartActivity class   int mPendingIntentId   123456  PendingIntent mPendingIntent   PendingIntent getActivity context  mPendingIntentId     mStartActivity  PendingIntent FLAG CANCEL CURRENT   AlarmManager mgr    AlarmManager context getSystemService Context ALARM SERVICE   mgr set AlarmManager RTC  System currentTimeMillis     100  mPendingIntent   System exit 0

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The only code that did not trigger  Your app has closed unexpectedly  is as follows  It s also non-deprecated code that doesn t require an external library  It also doesn t require a timer   public static void triggerRebirth Context context  Class myClass        Intent intent   new Intent context  myClass       intent addFlags Intent FLAG ACTIVITY NEW TASK   Intent FLAG ACTIVITY CLEAR TASK       context startActivity intent       Runtime getRuntime   exit 0

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fun triggerRestart context  Activity        val intent   Intent context  MainActivity  class java      intent addFlags Intent FLAG ACTIVITY NEW TASK      context startActivity intent      if  context is Activity             context as Activity  finish             Runtime getRuntime   exit 0

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try this   Intent intent   getPackageManager   getLaunchIntentForPackage getPackageName     intent addFlags Intent FLAG ACTIVITY CLEAR TOP   startActivity intent

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in MainActivity call restartActivity Method  public static void restartActivity Activity mActivity        Intent mIntent   mActivity getIntent        mActivity finish        mActivity startActivity mIntent

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You can restart your current activity like this   Fragment    activity  recreate     Activity     recreate

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I had to add a Handler to delay the exit    mgr set AlarmManager RTC  System currentTimeMillis     200  mPendingIntent           final Handler handler   new Handler            handler postDelayed new Runnable                  Override             public void run                     Runtime getRuntime   exit 0                            100

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You can simply call   public static void triggerRebirth Context context  Intent nextIntent        Intent intent   new Intent context  YourClass class       intent addFlags FLAG ACTIVITY NEW TASK       intent putExtra KEY RESTART INTENT  nextIntent       context startActivity intent       if  context instanceof Activity            Activity  context  finish               Runtime getRuntime   exit 0       Which is used in the ProcessPhoenix library    As an alternative   Here s a bit improved version of  Oleg Koshkin answer   If you really want to restart your activity including a kill of the current process  try following code  Place it in a HelperClass or where you need it   public static void doRestart Context c            try                 check if the context is given             if  c    null                      fetch the packagemanager so we can get the default launch activity                      you can replace this intent with any other activity if you want                 PackageManager pm   c getPackageManager                      check if we got the PackageManager                 if  pm    null                          create the intent with the default start activity for your application                     Intent mStartActivity   pm getLaunchIntentForPackage                              c getPackageName                                              if  mStartActivity    null                            mStartActivity addFlags Intent FLAG ACTIVITY CLEAR TOP                             create a pending intent so the application is restarted after System exit 0  was called                              We use an AlarmManager to call this intent in 100ms                         int mPendingIntentId   223344                          PendingIntent mPendingIntent   PendingIntent                                  getActivity c  mPendingIntentId  mStartActivity                                          PendingIntent FLAG CANCEL CURRENT                           AlarmManager mgr    AlarmManager  c getSystemService Context ALARM SERVICE                           mgr set AlarmManager RTC  System currentTimeMillis     100  mPendingIntent                             kill the application                         System exit 0                         else                           Log e TAG   Was not able to restart application  mStartActivity null                                            else                       Log e TAG   Was not able to restart application  PM null                                    else                   Log e TAG   Was not able to restart application  Context null                            catch  Exception ex                Log e TAG   Was not able to restart application                      This will also reinitialize jni classes and all static instances

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I have slightly modified Ilya Gazman answer to use new APIs  IntentCompat is deprecated starting API 26   Runtime getRuntime   exit 0  seems to be better than System exit 0     public static void triggerRebirth Context context        PackageManager packageManager   context getPackageManager        Intent intent   packageManager getLaunchIntentForPackage context getPackageName         ComponentName componentName   intent getComponent        Intent mainIntent   Intent makeRestartActivityTask componentName       context startActivity mainIntent       Runtime getRuntime   exit 0

User · Answer

The best way to fully restart an app is to relaunch it  not just to jump to an activity with FLAG ACTIVITY CLEAR TOP and FLAG ACTIVITY NEW TASK  So my solution is to do it from your app or even from another app  the only condition is to know the app package name  example   com example myProject     public static void forceRunApp Context context  String packageApp       Intent launchIntent   context getPackageManager   getLaunchIntentForPackage packageApp       launchIntent setFlags Intent FLAG ACTIVITY EXCLUDE FROM RECENTS   Intent FLAG ACTIVITY NEW TASK       context startActivity launchIntent       Example of usage restart or launch appA from appB   forceRunApp mContext   com example myProject appA      You can check if the app is running    public static boolean isAppRunning Context context  String packageApp       ActivityManager activityManager    ActivityManager  context getSystemService Context ACTIVITY SERVICE       List lt ActivityManager RunningAppProcessInfo gt  procInfos   activityManager getRunningAppProcesses        for  int i   0  i  lt  procInfos size    i              if  procInfos get i  processName equals packageApp                return true                      return false      Note  I know this answer is a bit out of topic  but it can be really helpful for somebody

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The application I m working on has to give the user the possibility to choose which fragments to display  fragments are dynamically changed at run-time   The best solution for me was to restart completely the application   So I tried plenty of solutions and none of them has worked for me  but this   final Intent mStartActivity   new Intent SettingsActivity this  Splash class   final int mPendingIntentId   123456  final PendingIntent mPendingIntent   PendingIntent getActivity SettingsActivity this  mPendingIntentId  mStartActivity                      PendingIntent FLAG CANCEL CURRENT   final AlarmManager mgr    AlarmManager  SettingsActivity this getSystemService Context ALARM SERVICE   mgr set AlarmManager RTC  System currentTimeMillis     100  mPendingIntent   this finishAffinity      notice here Runtime getRuntime   exit 0     notice here   Hoping that is going to help someone else

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With the Process Phoenix library  The Activity you want to relaunch is named  A    Java flavor      Java public void restart        ProcessPhoenix triggerRebirth context       Kotlin flavor      kotlin fun restart         ProcessPhoenix triggerRebirth context

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My best way to restart application is to use finishAffinity     Since  finishAffinity    can be used on JELLY BEAN versions only  so we can use ActivityCompat finishAffinity YourCurrentActivity this   for lower versions   Then use Intent to launch first activity  so the code will look like this   if  Build VERSION SDK INT  gt   Build VERSION CODES JELLY BEAN        finishAffinity        Intent intent   new Intent getApplicationContext    YourFirstActivity class       startActivity intent     else       ActivityCompat finishAffinity YourCurrentActivity this       Intent intent   new Intent getApplicationContext    YourFirstActivity class       startActivity intent       Hope it helps

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Directly start the initial screen with FLAG ACTIVITY CLEAR TASK and FLAG ACTIVITY NEW TASK

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Ok  I refactored my app and I will not finish A automatically  I let this run always and finish it through the onActivityResult event  In this way I can use the FLAG ACTIVITY CLEAR TOP   FLAG ACTIVITY NEW TASK flags to get what I want   public class A extends Activity         Override     protected void onActivityResult int requestCode  int resultCode  Intent data            super onActivityResult requestCode  resultCode  data           finish               protected void onResume             super onResume                           if  loggedIn                startActivityForResult new Intent this  MainActivity class   0             else               startActivityForResult new Intent this  LoginActivity class   0                       and in the ResultReceiver   Override public void onClick DialogInterface dialog  int which        MyApp factoryReset        Intent i   new Intent MyApp getContext    A class       i setFlags Intent FLAG ACTIVITY CLEAR TOP       i addFlags Intent FLAG ACTIVITY NEW TASK       MyApp getContext   startActivity i       Thanks anyway

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Jake Wharton recently published his ProcessPhoenix library  which does this in a reliable way  You basically only have to call   ProcessPhoenix triggerRebirth context     The library will automatically finish the calling activity  kill the application process and restart the default application activity afterwards

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IntentCompat makeMainSelectorActivity - Last tested on 11 2020 The app will be restored with the launcher activity and the old process will be killed  Works from Api 15  public static void restart Context context       Intent mainIntent   IntentCompat makeMainSelectorActivity Intent ACTION MAIN  Intent CATEGORY LAUNCHER       mainIntent addFlags Intent FLAG ACTIVITY NEW TASK       context getApplicationContext   startActivity mainIntent       System exit 0

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Try using FLAG ACTIVITY CLEAR TASK

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Here is an example to restart your app in a generic way by using the PackageManager   Intent i   getBaseContext   getPackageManager                 getLaunchIntentForPackage  getBaseContext   getPackageName      i addFlags Intent FLAG ACTIVITY CLEAR TOP   startActivity i

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I ve found that this works on API 29 and later - for the purpose of killing and restarting the app as if the user had launched it when it wasn t running   public void restartApplication final  NonNull Activity activity          Systems at 29 Q and later don t allow relaunch  but System exit 0  on       all supported systems will relaunch     but by killing the process  then       restarting the process with the back stack intact  We must make sure that       the launch activity is the only thing in the back stack before exiting     final PackageManager pm   activity getPackageManager       final Intent intent   pm getLaunchIntentForPackage activity getPackageName        activity finishAffinity       Finishes all activities     activity startActivity intent         Start the launch activity    System exit 0         System finishes and automatically relaunches us      That was done when the launcher activity in the app has this    lt intent-filter gt       lt action android name  android intent action VIEW   gt       lt action android name  android intent action MAIN    gt       lt category android name  android intent category LAUNCHER    gt   lt  intent-filter gt    I ve seen comments claiming that a category of DEFAULT is needed  but I haven t found that to be the case  I have confirmed that the Application object in my app is re-created  so I believe that the process really has been killed and restarted   The only purpose for which I use this is to restart the app after the user has enabled or disabled crash reporting for Firebase Crashlytics  According to their docs  the app has to be restarted  process killed and re-created  for that change to take effect

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Use   navigateUpTo new Intent this  MainActivity class      It works starting from API level 16  4 1   I believe

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There is a really nice trick  My problem was that some really old C   jni library leaked resources  At some point  it stopped functioning  The user tried to exit the app and launch it again -- with no result  because finishing an activity is not the same as finishing  or killing  the process   By the way  the user could go to the list of the running applications and stop it from there -- this would work  but the users just do not know how to terminate applications     If you want to observe the effect of this feature  add a static variable to your activity and increment it each  say  button press  If you exit the application activity and then invoke the application again  this static variable will keep its value   If the application really was exited  the variable would be assigned the initial value     And I have to comment on why I did not want to fix the bug instead  The library was written decades ago and leaked resources ever since  The management believes it always worked  The cost of providing a fix instead of a workaround    I think  you get the idea    Now  how could I reset a jni shared  a k a  dynamic   so  library to the initial state  I chose to restart application as a new process   The trick is that System exit   closes the current activity and Android recreates the application with one activity less   So the code is       This activity shows nothing  instead  it restarts the android process    public class MagicAppRestart extends Activity          Do not forget to add it to AndroidManifest xml         lt activity android name  your package name MagicAppRestart   gt       Override     protected void onCreate Bundle savedInstanceState            super onCreate savedInstanceState           System exit 0             public static void doRestart Activity anyActivity            anyActivity startActivity new Intent anyActivity getApplicationContext    MagicAppRestart class              The calling activity just executes the code MagicAppRestart doRestart this    the calling activity s onPause   is executed  and then the process is re-created  And do not forget to mention this activity in AndroidManifest xml  The advantage of this method is that there is no delays   UPD  it worked in Android 2 x  but in Android 4 something has changed

[android] How do I programmatically "restart" an Android app?

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