How to detect user inactivity in Android

public class MyApplication extends Application {
      private int lastInteractionTime;
      private Boolean isScreenOff = false; 
      public void onCreate() {
        super.onCreate();
        // ......   
        startUserInactivityDetectThread(); // start the thread to detect inactivity
        new ScreenReceiver();  // creating receive SCREEN_OFF and SCREEN_ON broadcast msgs from the device.
      }

      public void startUserInactivityDetectThread() {
        new Thread(new Runnable() {
          @Override
          public void run() {
            while(true) {
              Thread.sleep(15000); // checks every 15sec for inactivity
              if(isScreenOff || getLastInteractionTime()> 120000 ||  !isInForeGrnd)
                {
                  //...... means USER has been INACTIVE over a period of
                  // and you do your stuff like log the user out 
                }
              }
          }
        }).start();
      }

      public long getLastInteractionTime() {
        return lastInteractionTime;
      }

      public void setLastInteractionTime(int lastInteractionTime) {
        this.lastInteractionTime = lastInteractionTime;
      }

      private class ScreenReceiver extends BroadcastReceiver {

        protected ScreenReceiver() {
           // register receiver that handles screen on and screen off logic
           IntentFilter filter = new IntentFilter();
           filter.addAction(Intent.ACTION_SCREEN_ON);
           filter.addAction(Intent.ACTION_SCREEN_OFF);
           registerReceiver(this, filter);
        }

        @Override
        public void onReceive(Context context, Intent intent) {
          if (intent.getAction().equals(Intent.ACTION_SCREEN_OFF)) {
            isScreenOff = true;
          } else if (intent.getAction().equals(Intent.ACTION_SCREEN_ON)) {
            isScreenOff = false;
          }
        }
      }
    }

isInForeGrnd ===> logic is not shown here as it is out of scope of the question

You can wake the lock to the cpu by using the device code below-

  if(isScreenOff || getLastInteractionTime()> 120000 ||  !isInForeGrnd)
    {
      //...... means USER has been INACTIVE over a period of
      // and you do your stuff like log the user out 

      PowerManager pm = (PowerManager) context.getSystemService(Context.POWER_SERVICE);

      boolean isScreenOn = pm.isScreenOn();
      Log.e("screen on.................................", "" + isScreenOn);

      if (isScreenOn == false) {

        PowerManager.WakeLock wl = pm.newWakeLock(PowerManager.FULL_WAKE_LOCK | PowerManager.ACQUIRE_CAUSES_WAKEUP | PowerManager.ON_AFTER_RELEASE, "MyLock");

        wl.acquire(10000);
        PowerManager.WakeLock wl_cpu = pm.newWakeLock(PowerManager.PARTIAL_WAKE_LOCK, "MyCpuLock");

        wl_cpu.acquire(10000);
      }
    }

I came up with a solution that I find quite simple based on Fredrik Wallenius's answer. This a base activity class that needs to be extended by all activities.

public class MyBaseActivity extends Activity {

    public static final long DISCONNECT_TIMEOUT = 300000; // 5 min = 5 * 60 * 1000 ms


    private static Handler disconnectHandler = new Handler(new Handler.Callback() {
        @Override
        public boolean handleMessage(Message msg) {
            // todo
            return true;
        }
    });

    private static Runnable disconnectCallback = new Runnable() {
        @Override
        public void run() {
            // Perform any required operation on disconnect
        }
    };

    public void resetDisconnectTimer(){
        disconnectHandler.removeCallbacks(disconnectCallback);
        disconnectHandler.postDelayed(disconnectCallback, DISCONNECT_TIMEOUT);
    }

    public void stopDisconnectTimer(){
        disconnectHandler.removeCallbacks(disconnectCallback);
    }

    @Override
    public void onUserInteraction(){
        resetDisconnectTimer();
    }

    @Override
    public void onResume() {
        super.onResume();
        resetDisconnectTimer();
    }

    @Override
    public void onStop() {
        super.onStop();
        stopDisconnectTimer();
    }
}

I think you should go with this code, this is for 5min idle session timeout:->

Handler handler;
Runnable r;
@Override
protected void onCreate(Bundle savedInstanceState) {
    super.onCreate(savedInstanceState);
    setContentView(R.layout.activity_main);
    handler = new Handler();
    r = new Runnable() {

       @Override
       public void run() {
            // TODO Auto-generated method stub
            Toast.makeText(MainActivity.this, "user is inactive from last 5 minutes",Toast.LENGTH_SHORT).show();
        }
    };
    startHandler();
}
@Override
public void onUserInteraction() {
     // TODO Auto-generated method stub
     super.onUserInteraction();
     stopHandler();//stop first and then start
     startHandler();
}
public void stopHandler() {
    handler.removeCallbacks(r);
}
public void startHandler() {
    handler.postDelayed(r, 5*60*1000); //for 5 minutes 
}

I don't know a way of tracking inactivity but there is a way to track user activity. You can catch a callback called onUserInteraction() in your activities that is called every time the user does any interaction with the application. I'd suggest doing something like this:

@Override
public void onUserInteraction(){
    MyTimerClass.getInstance().resetTimer();
}

If your app contains several activities, why not put this method in an abstract super class (extending Activity) and then have all you activities extending it.