Problem with back button in my app [closed]

Answer 1

How can you clear SharedPreference when the device is switched off.

You can clear it when the device starts thru BraodcastReceiver.

public class PhoneStateReceiver extends BroadcastReceiver{

    @Override
    public void onReceive(final Context context, Intent intent) {

        if(intent.getAction().equals(Intent.ACTION_BOOT_COMPLETED)){
            //Clear your `SharedPreference` here.
        }
    }
}

In your manifest add this:

Add permission: