Develop Reference

What is the difference between `finishAffinity();` and `finish()` methods in Android?

I've using some code for a sign in screen that forces the app to close if the user doesn't want to sign in. If the user chooses to not sign in/cancel, it calls the code to exit the app. I've successfully done this two ways (not at the same time) with:
finishAffinity();
System.exit(0);
and
finish();
System.exit(0);
Yet both lines of code seem to do the same thing... The app is closed to the user, yet remains in the background apps to be reopen if the user hits the 'overview' button they can select it to reopen. (Which just restarts the prompt to sign in.)
Since I notice no functional difference, I'm wondering what is the difference between finishAffinity() and finish() methods?
Bonus Question: Also, is there a way to completely shut down the app, so it also doesn't appear in the overview button app list?

finishAffinity():
Closes all the activities present in the current Stack
finish()
Closes only opened activity
Also, is there a way to completely shut down the app, so it also
doesn't appear in the overview button app list?
Yes you can add android:noHistory="true" to your activities tag in the Manifest.xml for this pupose

finishAffinity() : finishAffinity() is not used to "shutdown an application". It is used to remove a number of Activities belonging to a specific application from the current task (which may contain Activities belonging to multiple applications).
Even if you finish all of the Activities in your application, the OS process hosting your app does not automatically go away (as it does when you call System.exit()). Android will eventually kill your process when it gets around to it. You have no control over this (and that is intentional).
finish() : When calling finish() in an activity, the method onDestroy() is executed this method can do things like:
Dismiss any dialogs the activity was managing.
Close any cursors the activity was managing.
Close any open search dialog.

finishAndRemoveTask() method pop out all your activities from stack and removes the application from recent task list simple finish this current activity as well as all activities immediately below it in the current task that have the same affinity,
finish() method pop out your current activity from stack.
for detail document link
finishAffinity(): finish the current activity and all activities immediately below it in the current task that have the same affinity.
finishAndRemoveTask(): call this when your activity is done and should be closed and the task should be completely removed as a part of finishing the root activity of the task.

Android Intent open new activities but did not close the old one

I searched through most answers here and all suggest we add a flag to the intent to kill old activities. The problem is my activity only receive intents from other app and has no control over it.
More specifically, my activity receive an intent to load a picture, then it uses Asynctask to load and do some complicated background processing of that picture, say, may be 2 minutes.
If the user at this moment back out (assuming that only onStop is called, not yet onDestroy) and share another picture to the app , this will start a new activity, and the previous activity cannot be accessed, but its Asynctask hold up the thread so that my new activity just freeze without starting its own Asynctask.
(I later tried the parallel thread executor, but this doesn't stop the old thread from running, thus consuming computational resources).
Any idea what I should do?
(I don't want to stop the task in onStop as this is to easy to be called. But I do want to stop the task if new picture is shared, since it is no longer needed.)
(The Asynctask will spit out a huge array of self-defined Objects declared in the main activity, and thus the activity gets immediate updates of the result from the background process, and the UI updates immediately after onPostExecute is called.)

EDIT:
It seems that your problem is that you're trying to do all this image processing work in asynctasks launched by your activity. Have you considered changing your app architecture to rely all this background processing to a service?
You can use the activity to show some UI information while you process the image in your service, or if you don't need this UI just simply communicate with the service (through broadcast, for example) to provide it the image and let the service show some information of the process through notifications.
If you don't want to keep your activity alive when you exit it you can use
android:noHistory="true" in your activity declaration at the manifest
More info here

This is the workaround, and seems it is working very well for the moment:
After getting a sharedpreference prefs, do this in onCreate:
prefs.edit().putBoolean("ForceClose", true).commit();
In the onPreExecute() of the AsyncTask, put:
prefs.edit().putBoolean("ForceClose", false).commit();
In the doInBackground() of the AsyncTask, constantly check for
if (prefs.getBoolean("ForceClose", false))
cancel(true);
and call finish() in onCancelled() to finish off the activity.

Resume previous activity from broadcast receiver

here's my problem:
I'm in activity A
Activity A starts a new activity B to call a number (Intent.ACTION_CALL)
How is it possible to resume activity A - I don't want to finish activity B, I simply want to bring activity A to the front
At the moment I have a broadcastReceiver which is able to start a new instance of activity A when the call takes place. If I start activity A from there with "FLAG_ACTIVITY_SINGLE_TOP", I get the error
Calling startActivity() from outside of an Activity
context requires the FLAG_ACTIVITY_NEW_TASK flag.
Is this really what you want?
But I don't want a new task, I want to RESUME activity A
Thanks a lot!
EDIT:
Perhaps I could simply simulate a click on the BACK-button?

Considering your use case - BroadcastReceiver that doesn't have a tasks in which to start the activity - singleTask in the manifest should do what you want.
"singleTask"
The system creates a new task and instantiates the activity at the root of
the new task. However, if an instance of the activity already exists in a
separate task, the system routes the intent to the existing instance through
a call to its onNewIntent() method, rather than creating a new instance.
Only one instance of the activity can exist at a time.
Note: Although the activity starts in a new task, the Back
button still returns the user to the previous activity.
Taken from: http://developer.android.com/guide/components/tasks-and-back-stack.html

Have you tried using FLAG_ACTIVITY_REORDER_TO_FRONT ?
http://developer.android.com/reference/android/content/Intent.html#FLAG_ACTIVITY_REORDER_TO_FRONT
It seems to do exactly what you need.

How to run activity, if app in background?

I writing the network application and i have a problem with starting activity if the application in background. I want to start activity when some data comes to network. In my Actity A a have a receiver and when it receive some answer from server, it must run the Activity B. But if the App in background, Activity B not starting and metod onCreate() doesn`t execute. It execute only when the user go back to App. But its not really what i want, becouse in Activity B i need to start timer and i neen to enable GPS and some other work. Besides that, Activity B receive some data too, and if B not existing - this receiver will never receive anything.
I tryed IntentServise, but its not working - result the same as without him.
Any ideas? Thanks for any information :-)

Maybe your receiver is not getting intents when your app is background, for example if you're unregistering it in onDestroy method...
try declaring your broadcast receiver in manifest. In broadcast receiver class use starActivity to call act B. This works for me.
If you still have some problems maybe you should provide some source code(for example function where you're working with intents) to clarify your question.

You can't force activity to come back from background. You can use status bar to show notification for a user. Think also about it that this a mobile device, someone can in the middle of conversation or use GPS as navigation in car.

Android broadcast receiver when the app is in background

I'm facing a problem with the android broadcast receiver. I have a login page and after a successful login the app goes to another activity. And it contains a broadcast receiver. I am sending a broadcast once a separate service completes its action. The app works fine in a happy day scenario.
My problem here is, after i entered the username / password and hit the login button i send the app to the background. But when the app is in background that broadcast receiver wont receive the broadcast which i'm sending.
Anyone have a clue regarding this issue ?
Any help would be greatly appreciated.
Thanks in advance.

Are you unregistered the broadcast receiver in any of the activities onPause/OnStop/OnDestroy method? if yes then you will not receive the broadcast. make sure you have register the Broadcast receiver in the AndroidManifest. and not unregistered. if you wanted to receive intent in the background then you should not unregistered it.

Is you start separate service in another Activity right after you hit the login button ?
Because service is the entity that ment to run on the background.
If your answer is yes, i think you should consider to check the lifecycle of the activity, because there is possibility that when you hit the login button, you send your application on the background. Now, at this point activity inserts to onPause. Therefore your second activity is not active and as a result can't call to the service.
I hoped it will you help to resolve your problem :)

Are you unregistered the broadcast receiver in any of the activities onPause/OnStop/OnDestroy method? if yes then you will not receive the broadcast. make sure you have register the Broadcast receiver in the AndroidManifest. and not unregistered. if you wanted to receive intent in the background then you should not unregistered it.
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If you start separate service in another Activity right after you hit the login button ? Because service is the entity that ment to run on the background.
If your answer is yes, i think you should consider to check the lifecycle of the activity, because there is possibility that when you hit the login button, the application will be in background. Now, at this point activity inserts to onPause(). Therefore your second activity is not active and as a result can't call to the service.