terminate a thread when exiting an activity (android)

Question

I have a thread created inside a secondary activity on Android, like so:

new Thread(new Runnable() {
                public void run() {
                    try {
                        String branch=spinner.getSelectedItem().toString();

                        while( branch.equals(spinner.getSelectedItem().toString())){
                            System.out.println("----LOOPER."+spinner.getSelectedItem().toString());
                            GetQinfo a= (GetQinfo) new GetQinfo().execute(city,type,org,spinner.getSelectedItem().toString());
                            Thread.sleep(refreshRate);                              
                        }
                    } catch (InterruptedException e){
                        e.printStackTrace();
                    } 
                 return;
                }
              }).start();

the problem is that when i go back to the main activity this thread is still running. what i did was on the goback button to write this:

spinner.setSelection(0);
this.finish();

This way the value of the spinner is changed, causing the while loop on the thread to return false, thus exiting the thread. But i dont think this is the right way of doing it. can anyone suggest something different, or should i say, better

[How to stop a java thread gracefully?](http://stackoverflow.com/questions/3194545/how-to-stop-a-java-thread-gracefully) — Subhrajyoti Majumder, Oct 30 '14 at 09:26
Basically, once thread task gets completed meaning code inside gets executed, it gets reclaimed by to GC later — ajduke, Oct 30 '14 at 09:31
I just thought that there should be a way to terminate all running threads when the activity terminates. if the only way of doing it is by using some variable as flag, then i got it right. — Skaros Ilias, Oct 30 '14 at 09:37

score 1 · Answer 1 · answered Oct 30 '14 at 09:28

You should use interrupt() method of the thread when you leave the activity.

YourThread.interrupt();

new Thread(new Runnable() {
                public void run() {
                    try {
if(!Thread.interrupted())
                        String branch=spinner.getSelectedItem().toString();

                        while( branch.equals(spinner.getSelectedItem().toString())){
                            System.out.println("----LOOPER."+spinner.getSelectedItem().toString());
                            GetQinfo a= (GetQinfo) new GetQinfo().execute(city,type,org,spinner.getSelectedItem().toString());
                            Thread.sleep(refreshRate);                              
                        }
                    } catch (InterruptedException e){
                        e.printStackTrace();
                    } 
                 return;
                }
              }).start();

score 0 · Accepted Answer · answered Oct 30 '14 at 09:27

There is no method explicitly available to stop a thread. There were methods previously to stop the thread but they were deprecated. Please read the following link to see why the developers of java wanted it this way: http://docs.oracle.com/javase/1.5.0/docs/guide/misc/threadPrimitiveDeprecation.html

According to this document, they prefer that you do it in the manner that you suggested. So you're not wrong.

score 0 · Answer 3 · answered Oct 30 '14 at 09:31

 private volatile boolean stopThread;

   public void run() {
      String branch=spinner.getSelectedItem().toString();
      while (!stopThread) {
        System.out.println("----LOOPER."+spinner.getSelectedItem().toString());
        GetQinfo a= (GetQinfo) new GetQinfo().execute(city,type,org,spinner.getSelectedItem().toString());
        Thread.sleep(refreshRate); 
      }
   }


public void stopThread() {
    stopThread = true;
    thread.interrupt();
}

Thats almost the way i have it, using a variable as flag, isnt it? — Skaros Ilias, Oct 30 '14 at 09:46

terminate a thread when exiting an activity (android)

3 Answers3