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How do I return to previous app after a service generated activity is 'finished'

My app has a service that runs in the background. It wakes up on intent from the user which is typically generated from another application (such as sharing to my app from the web browser). After the service is done performing a task I want it to open an Activity that displays some info about the task that was completed. When the user is done looking at this info, I want them to be able to hit 'Back' or 'Close' and return to what they were doing previously (not within my application).
I've only managed to get the activity to close leaving my App's main activity front and center on the screen. This only happens if the app is still running. If it's been killed then it correctly returns to the web browser where the user intent was generated from.
How can I make the 'Back' button close the activity and return to the previous app from which this entire workflow was started?
EDIT:
This is the code I am executing from within the android service:
Intent intent = new Intent(this, TestActivity.class);
intent.setFlags(Intent.FLAG_ACTIVITY_NEW_TASK | Intent.FLAG_ACTIVITY_CLEAR_TOP);
startActivity(intent);
When I tap the back button from the TestActivity it returns me to the main activity of my app, not the previous app I was in when the service started TestActivity.

In second line you are using Intent.FLAG_ACTIVITY_CLEAR_TOP which is clearing your previous activity

startActivity opens last app in background instead of needed activity

I got an app which can receive an event (which is basically a message from a service in the background), and when it does, I am invoking this code:
Intent dialogIntent = new Intent(this, MainActivity.class);
dialogIntent.setFlags(Intent.FLAG_ACTIVITY_CLEAR_TOP);
dialogIntent.addFlags(Intent.FLAG_ACTIVITY_NEW_TASK);
startActivity(dialogIntent);
This code is supposed to return the app to the front so the user can handle the event.
This code works only if the app I'm working on was also the last app the user has been in. The code doesn't work in these scenarios:
1) The user has paused the app, opened another app and then paused it too so the 2nd app is the last in the background - in which case the last app will always open, even though I'm starting my MainActivity. For example, if I've moved my app to the background, opened Android's settings and then an event is received, the Android's settings screen will open instead of my app.
2) The user is inside another app. In which case, the app won't be brought to the front at all.
How can I made the specific app to be resumed from the background no matter what?

Use launcher category as below:
Intent resumeIntent = new Intent(context, MainActivity.class);
resumeIntent.setAction(Intent.ACTION_MAIN);
resumeIntent.addCategory(Intent.CATEGORY_LAUNCHER);
startActivity(resumeIntent);
Also add android:launchMode="singleTop" in the manifest of your activity.

You can add android:launchMode="singleTop" in the manifest for the Activity.

Detect if user starts an application, android

Thanks in advance for the help.
I have an app that can be started by either the user physically starting the app (like you would any normal app) or by a repeating service. Depending on what starts the app (the user or the service) I want to preform different initialization actions. How might I be able to detect if an user starts the app without doing anything custom (I imagine that there has to be some kind of built in setting in android for me to determine this)?

If service, that starts your Activity, is yours service, you can put some custom information (using Intent#putExtra for example) in Intent you use to start Activity from Service.
In Activity you can use Activity#getIntent(), that returns the intent that started this activity.
If you started Activity from Service, that Intent will be the one you passed in Service#startActivity, and will have your custom information. Otherwise, that was not your Service, that started your Activity.
That could look somehow like that, for example:
//in Activity
public static final String EXTRA_STARTED_FROM_MY_SERVICE = "com.example.extra_started_from_sevice";
private boolean wasActivityStartedFromService() {
Intent startingIntent = getIntent();
//assuming you will use Intent#putExtra in your service when starting activity
return startingIntent.getBooleanExtra(EXTRA_STARTED_FROM_MY_SERVICE, false);
}
//...
//in Service
//...
Intent startingIntent = new Intent(this, MainActivity.class);
startingIntent.putExtra(MainActivity.EXTRA_STARTED_FROM_MY_SERVICE, true);
startActivity(startingIntent);

Android intent service onClick, or start new activity and then Asynctask

Many times in android apps, users click a button/view and start a new activity, where the new activity pops up in front of what the user was previously looking at, and loads data.
Would there be any difference from a user perspective if the data started loading (from network or disk or both) when the user clicked the button before the next activity started. And then that data was returned to the new activity in a broadcast receiver.
This is compared to starting the process in the oncreate of the activity. Assuming these network and i/o processes only take milliseconds either way, would it make a difference to the user if the methods were started in onCreate of the new activity, or started in the old activity onClick.
First way, starting I/O and changing views after I/O finishes
//first activity
public void onClick(View v){
startActivity(new Intent(this, NewActivity.class);
}
//NewActivity.class
onCreate(Bundle mBundle){
super.onCreate(mBundle);
setContentView(R.layout.mView);
mObject = networkCall(); //after network call, the view objects in this layout will reflect data from the network call
}
second way, starting the I/O in the first activity
//first activity
public void onClick(View v){
IntentService networkCall = new IntentService();
//start network call
startActivity(new Intent(this, NewActivity.class);
}
//second activity on create just sets the view and also broadcast receiver
My GUESS is that in the split second that it takes for the activity to pop up, the data from the intent service could become available. But at the same time, passing data via intent could take just as long making the benefits marginal
Insight appreciated

In my experience the onCreate() of your new activity is called almost instantly from when you call startActivity(). The new activity doesn't show up right way because it has to take time to render your layout.
You could play around with timings yourself by using the Log.d() function. Something like Log.d(TAG, "This happend at: " + System.currentTimeMillis()); at different points in your code to see when things happen. Watch the LogCat while your apps runs and you can decide for your self which way is better.

Clear all current activities and start a new activity in background?

I have an application where after a certain amount of time I want all activities in the app's stack to be removed and replaced by a login activity screen. I've got a Runnable timer that issues this set of statements:
Intent intent = new Intent( ctx, mainActivity.class );
intent.setFlags( Intent.FLAG_ACTIVITY_CLEAR_TOP );
ctx.startActivity( intent );
This works fine when my app is in the foreground, however, when my app is in the background and I'm using another app (say, the Web Browser), the timer fires as it should and pops up the login activity screen to the foreground.
What I want is for the login activity to be activated and moved to the front of the stack, and have all other activities in the stack removed, but not have the app and activity popped to the foreground over any currently running app.
Is there any way to do this with a different method or flag? Thanks.

You could probably finish() the login activity in the onCreate event, conditional on an intent extra. Hopefully it would then be closed before it is displayed...