Question

I hope it exists.

I would like to store the time when the application loses focus and then check if it has lost focus for more than n-minutes to bring up a lock.

Seeing how an application is composed of activities, I think there will not be a direct equivalent. How would I be able to achieve similar results?

EDIT
I tried to extend the Application class to registerActivityLifecycleCallbacks() and realized I will not be able to use this approach because it is only available in API Level 14+

Answer 1

Allow me to share how I made a backwards compatible solution.

I had already implemented the locking of my app on launch if there was a passcode associated with the account. To be complete, I needed to handle situations where other applications (including the home activity) take over for n-minutes.

I ended up making a BaseActivity that all my Activities extend.

// DataOperations is a singleton class I have been using for other purposes.
/* It is exists the entire run time of the app
   and knows which activity was last displayed on screen.
   This base class will set triggeredOnPause to true if the activity before
   "pausing" because of actions triggered within my activity.  Then when the
   activity is paused and triggeredOnPause is false, I know the application
   is losing focus.

   There are situations where an activity will start a different application 
   with an intent.  In these situations (very few of them) I went into those 
   activities and hard-coded these lines right before leaving my application

   DataOperations datao = DataOperations.sharedDataOperations();
   datao.lostFocusDate = new Date();
*/

import java.util.Date;

import android.app.Activity;
import android.content.Intent;
import android.util.Log;

public class BaseActivity extends Activity {
    public boolean triggeredOnPause;

    @Override 
    public void onResume(){
        super.onResume();
        DataOperations datao = DataOperations.sharedDataOperations();
        if (datao.lostFocusDate != null)    {
            Date now = new Date();
            long now_ms = now.getTime();
            long lost_focus_ms = datao.lostFocusDate.getTime();
            int minutesPassed = (int) (now_ms-lost_focus_ms)/(60000);
            if (minutesPassed >= 1) {
                datao.displayLock();
            }
                    datao.lostFocusDate = null;
        }
        triggeredOnPause = false;
    }

    @Override
    public void onPause(){
        if (triggeredOnPause == false){
            DataOperations datao = DataOperations.sharedDataOperations();
            datao.lostFocusDate = new Date();
        }
        super.onPause();
    }
    @Override
    public void startActivity(Intent intent)
    {
        triggeredOnPause = true;
        super.startActivity(intent);
    }
    @Override
    public void startActivityForResult(Intent intent, int requestCode)  {
        triggeredOnPause = true;
        super.startActivityForResult(intent, requestCode);
    }

}

If you are going to use this solution and have trouble implementing the equivalent of my DataOperations class, please comment and I can post the necessary code.