Android - running a method periodically using postDelayed call

Question

I have a situation in an Android app where I want to start a network activity  sending out some data  which should run every second  I achieve this as follows   In the onCreate   I have the code   tv   new TextView this   tv postDelayed sendData  1000     The sendData   function      Handler handler   new Handler       private Runnable sendData new Runnable        public void run            try                 prepare and send the data here               handler removeCallbacks sendData               handler postDelayed sendData  1000                         catch  Exception e                e printStackTrace                            The problem come in like this  When user presses the back buttons and app comes out  UI disappears  the sendData   function still gets executed which is what I want   Now when user re-starts the app  my onCreate   gets called again and I get sendData   invoked twice a second  It goes on like that   Every time user comes out and starts again  one more sendData   per second happens     What am I doing wrong   Is it my new Handler   creating problem   What is the best way to handle this   I want one sendData   call per second until user quits the app  form application manager

User · Answer

Handler h   new Handler          Override     public void handleMessage Message msg            super handleMessage msg           if  msg what  0                  do stuff             h removeMessages 0       clear the handler for those messages with what   0             h sendEmptyMessageDelayed 0  2000                          h sendEmptyMessage 0

User · Answer

You can simplify the code like this   In Java   new Handler   postDelayed     - gt          your code here    1000     In Kotlin   Handler   postDelayed        your code here    1000

User · Answer

Please check the below  its working on my side in below code your handler will run after every 1 Second when you are on same activity   HandlerThread handlerThread   new HandlerThread  HandlerThread                    handlerThread start                    handler   new Handler handlerThread getLooper                     runnable   new Runnable                                          Override                     public void run                                                      handler postDelayed this  1000                                                                handler postDelayed runnable  1000

User · Answer

final Handler handler   new Handler        handler postDelayed new Runnable            Override       public void run               Do something after 100ms         Toast makeText c   check   Toast LENGTH SHORT  show              handler postDelayed this  2000                  1500

User · Answer

I think you could experiment with different activity flags  as it sounds like multiple instances    singleTop    singleTask    singleInstance   Are the ones I would try  they can be defined inside the manifest   http   developer android com guide topics manifest activity-element html

User · Answer

Perhaps involve the activity s life-cycle methods to achieve this   Handler handler   new Handler      Override protected void onCreate Bundle savedInstanceState          super onCreate savedInstanceState         handler post sendData       Override protected void onDestroy           super onDestroy          handler removeCallbacks sendData       private final Runnable sendData   new Runnable        public void run            try                 prepare and send the data here                 handler postDelayed this  1000                         catch  Exception e                e printStackTrace                            In this approach  if you press back-key on your activity or call finish     it will also stop the postDelayed callings

User · Answer

You should set andrid allowRetainTaskState  true  to Launch Activity in Manifest xml  If this Activty is not Launch Activity  you should set android launchMode  singleTask  at this activity

User · Answer

Why don t you create service and put logic in onCreate    In this case even if you press back button service will keep on executing  and once you enter into application it will not call onCreate   again  Rather it will call onStart

[android] Android - running a method periodically using postDelayed() call

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