Question

I can’t find any working solution to stopping/resuming a thread when locking/unlocking a device, can anyone help, or tell me where I can find how to do it? I need stop the thread when the phone is locked and start it again when the phone is unlocked.

Answer 1

Java operates on a cooperative interrupt model for stopping threads. That means you can’t simply stop a thread mid-execution without cooperation from the thread itself. If you want to stop a thread the client can call Thread.interrupt() method to request the thread stop:

public class SomeBackgroundProcess implements Runnable {

    Thread backgroundThread;

    public void start() {
       if( backgroundThread == null ) {
          backgroundThread = new Thread( this );
          backgroundThread.start();
       }
    }

    public void stop() {
       if( backgroundThread != null ) {
          backgroundThread.interrupt();
       }
    }

    public void run() {
        try {
           Log.i("Thread starting.");
           while( !backgroundThread.interrupted() ) {
              doSomething();
           }
           Log.i("Thread stopping.");
        } catch( InterruptedException ex ) {
           // important you respond to the InterruptedException and stop processing 
           // when its thrown!  Notice this is outside the while loop.
           Log.i("Thread shutting down as it was requested to stop.");
        } finally {
           backgroundThread = null;
        }
    }

The important part of threading is that you don’t swallow InterruptedException and instead stop your thread’s loop and shutdown because you only get this exception if a client has request the thread interrupt itself.

So you simply need to hook up the SomeBackgroundProcess.start() to the event for unlock, and hook up the SomeBackgroundProcess.stop() to the lock event.