Android - Best and safe way to stop thread

Question

I want to know which is the best way to stop a thread in Android  I know I can use AsyncTask instead of it and that there is a cancel   method  I have to use Threads in my situation  Here is how I m using Thread   Runnable runnable   new Runnable              Override         public void run                   doing some work                  new Thread runnable  start      So  does anyone have any idea of which is the best way to stop a thread

User · Answer

This situation isn t in any way different from the standard Java  You can use the standard way to stop a thread   class WorkerThread extends Thread       volatile boolean running   true       public void run                Do work            if   running  return            Continue doing the work           The main idea is to check the value of the field from time to time  When you need to stop your thread  you set running to false  Also  as Chris has pointed out  you can use the interruption mechanism   By the way  when you use AsyncTask  your apporach won t differ much  The only difference is that you will have to call isCancel   method from your task instead of having a special field  If you call cancel true   but don t implement this mechanism  the thread still won t stop by itself  it will run to the end

User · Answer

Inside of any Activity class you create a method that will assign NULL to thread instance which can be used as an alternative to the depreciated stop   method for stopping thread execution   public class MyActivity extends Activity    private Thread mThread      Override public void onCreate Bundle savedInstanceState        super onCreate savedInstanceState       setContentView R layout main             mThread    new Thread             Override         public void run                   Perform thread commands        for  int i 0  i  lt  5000  i                   do something                  Call the stopThread   method              stopThread this                                  Start the thread          mThread start        private synchronized void stopThread Thread theThread        if  theThread    null                theThread   null              This works for me without a problem

User · Answer

I used this method   Looper myLooper   quit      you can try

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The thing is you need to check whether the thread is running or not     Field   private boolean runningThread   false    In the thread   new Thread new Runnable                  Override             public void run                     while  true                        try                           Thread sleep  long  Math floor speed                            if   runningThread                                return                                                    yourWork                          catch  InterruptedException e                            e printStackTrace                                                                     start      If you want to stop the thread you should make the below field      private boolean runningThread   false

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The Thread stop   method that could be used to stop a thread has been deprecated  for more info see  Why are Thread stop  Thread suspend and Thread resume Deprecated    Your best bet is to have a variable which the thread itself consults  and voluntarily exits if the variable equals a certain value  You then manipulate the variable inside your code when you want the thread to exit  Alternately of course  you can use an AsyncTask instead

User · Answer

Currently and unfortunately we can t do anything to stop the thread      Adding something to Matt s answer we can call interrupt   but that doesn t stop thread    Just tells the system to stop the thread when system wants to kill some threads  Rest is done by system  and we can check it by calling interrupted      p s    If you are really going with interrupt   I would ask you to do some experiments with a short sleep after calling interrupt

User · Answer

You should make your thread support interrupts  Basically  you can call yourThread interrupt   to stop the thread and  in your run   method you d need to periodically check the status of Thread interrupted    There is a good tutorial here

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There are 2 following ways preferred to stop a thread   Create a volatile boolean variable and change its value to false and check inside the thread  volatile isRunning   false   public void run     if  isRunning   return               Or you can use the interrupt   method which can be receive inside a thread  SomeThread interrupt     public void run     if Thread currentThread isInterrupted     return

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As we know that the Thread stop   is deprecated in JAVA  under the hood the Thread stop calls the interrupt   method on the thread to stop it  Interrupt is meant to be thrown from the methods which keep the thread waiting for some other thread to notify after the execution completes  Interrupt will cause nothing to the thread if it is not handled in the execution of a thread  like  if Thread interrupted   return  So  all in all we need to basically manage the start and stop of the thread like calling the start   method like Thread start   starts a while true  inside the run   method of the thread and checks for interrupted status in each iteration and returns from the thread  Please note that a thread will not die in the following situations   The thread has not yet returned from the run    Any of the objects owned by the thread is accessible   This hints to null dispose of the references for GC to do the rest

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On Android the same rules apply as in a normal Java environment  In Java threads are not killed  but the stopping of a thread is done in a cooperative way  The thread is asked to terminate and the thread can then shutdown gracefully   Often a volatile boolean field is used which the thread periodically checks and terminates when it is set to the corresponding value   I would not use a boolean to check whether the thread should terminate  If you use volatile as a field modifier  this will work reliable  but if your code becomes more complex  for instead uses other blocking methods inside the while loop  it might happen  that your code will not terminate at all or at least takes longer as you might want      Certain blocking library methods support interruption    Every thread has already a boolean flag interrupted status and you should make use of it  It can be implemented like this   public void run         try         while  Thread currentThread   isInterrupted                                   catch  InterruptedException consumed           Allow thread to exit             public void cancel     interrupt        Source code taken from Java Concurrency in Practice  Since the cancel   method is public you can let another thread invoke this method as you wanted   There is also a poorly named static method interrupted which clears the interrupted status of the current thread

User · Answer

My requirement was slightly different than the question  still this is also a useful way of stopping the thread to be executing its tasks  All I wanted to do is to stop the thread on exiting the screen and resumes while returning to the screen   As per the Android docs  this would be the proposed replacement for stop method which has been deprecated from API 15     Many uses of stop should be replaced by code that simply modifies some   variable to indicate that the target thread should stop running  The   target thread should check this variable regularly  and return from   its run method in an orderly fashion if the variable indicates that it   is to stop running    My Thread class     class ThreadClass implements Runnable                                      Override                         public void run                                 while  count  lt  name length                                       if   exited     checks boolean                                                                             perform your task                                                                          OnStop and OnResume would look like this     Override     protected void onStop             super onStop            exited   true              Override     protected void onResume             super onResume            exited   false

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Try Like this Thread thread   new Thread          Override     public void run             Looper prepare               while true                Log d  quot Current Thread quot    quot Running quot                 try                 Thread sleep 1000                catch Exeption exception                         thread start    thread interrupt

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If there is thread class with a handler in your project  when you started from one of the fragment class if you wanted to stop here is the solution how to stop and avoid crashing the app when fragment removes from the stack   This code is in Kotlin  It perfectly works   class NewsFragment   Fragment          private var mGetRSSFeedsThread  GetRSSFeedsThread    null      private val mHandler   object   Handler              override fun handleMessage msg  Message                   if  msg  what    GetRSSFeedsThread GETRSSFEEDSTHREAD SUCCESS                    val updateXMLdata   msg obj as String                 if   updateXMLdata isNullOrEmpty                        parseUpdatePager CommonUtils getJSONObjectFromXML updateXMLdata  toString                   else if  msg  what    GetRSSFeedsThread GETRSSFEEDSTHREAD SUCCESS                    BaseActivity make toast activity  resources getString R string pleaseTryAgain                                      private var rootview  View    null      override fun onCreateView inflater  LayoutInflater   container  ViewGroup   savedInstanceState  Bundle    View            rootview   inflater  inflate R layout fragment news  container  false            news listView   rootview  findViewById R id news listView          mGetRSSFeedsThread   GetRSSFeedsThread this activity  mHandler            if  CommonUtils isInternetAvailable activity                 mGetRSSFeedsThread  start                       return rootview            override fun onCreate savedInstanceState  Bundle             super onCreate savedInstanceState          setHasOptionsMenu true                 override fun onAttach context  Context             super onAttach context          println  onAttach              override fun onPause             super onPause           println  onPause fragment may return to active state again            Thread interrupted               override fun onStart             super onStart           println  onStart               override fun onResume             super onResume           println  onResume fragment may return to active state again               override fun onDetach             super onDetach           println  onDetach fragment never return to active state again               override fun onDestroy             super onDestroy            println  onDestroy fragment never return to active state again            check the state of the task         if  mGetRSSFeedsThread    null  amp  amp  mGetRSSFeedsThread  isAlive                  mGetRSSFeedsThread  interrupt              else                          override fun onDestroyView             super onDestroyView           println  onDestroyView fragment may return to active state again                 override fun onStop             super onStop           println  onStop fragment may return to active state again                Above code stops the running thread when you switch to any other fragment or activity from current fragment  also it recreates when you return to current fragment

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This worked for me like this  Introduce a static variable in main activity and regularly check for it how i did was below   public class MainActivity extends AppCompatActivity       This is the static variable introduced in main activity public static boolean stopThread  false       protected void onCreate Bundle savedInstanceState         super onCreate savedInstanceState       setContentView R layout activity main        Thread thread   new Thread new Thread1         thread start         Button stp thread  findViewById R id button stop        stp thread setOnClickListener new Button OnClickListener                Override            public void onClick View v                 stopThread   true                                class Thread1 implements Runnable           public void run                 YOU CAN DO IT ON BELOW WAY          while  MainActivity stopThread                 Do Something here                       OR YOU CAN CALL RETURN AFTER EVERY LINE LIKE BELOW          process 1 goes here             Below method also could be used         if stopThread  true               return                        use this after every line            process 2 goes here              Below method also could be used         if stopThread  true               return                        use this after every line           process 3 goes here              Below method also could be used         if stopThread  true               return                        use this after every line           process 4 goes here

[android] Android - Best and safe way to stop thread

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