Develop Reference

Remove app completely from memory on exit

I am building an Android app, which starts a service that keeps running in the background. When the user uses the Home button to close one of the activities (which communicate with the service), and then navigates to the app again, they get the last activity. This is correct behaviour.
However, when I explicitly stop the service (via an option in the menu), the app should "Quit". Currently, that works like this:
stopService(new Intent(this, MyService.class));
finish();
// just go to to the home screen, as it is intended in Android
Intent intent = new Intent(Intent.ACTION_MAIN);
intent.addCategory(Intent.CATEGORY_HOME);
intent.setFlags(Intent.FLAG_ACTIVITY_NEW_TASK);
startActivity(intent);
and that works fine. But when I now navigate to the app again, it starts the previously opened Activity. What I want is that it starts the starting activity again (the launcher).
How could I accomplish that?

System.exit(0);
But you should have only one Activity in stack.

If you look at the description of android:excludeFromRecents it says:
Whether or not the task initiated by this activity should be excluded from the list of recently used applications ("recent apps").
isn't this what you are looking for ? Once the user hits exit, this app won't be in the recently used apps and hence will be completely removed from memory ? :)

I think that removing 'the app completely from memory on exit' is not the issue. Even if you stop your service the process is likely to remain in memory - that is the systems' decision.
You want an explicit, custom behaviour - user chooses your 'exit' option from menu --> next app launch starts at main activity - so you will need to handle this explicitly.
The default behaviour is that the user returns to their last activity when they re-launch. So they only return to the main activity if they exit by 'backing out' through your activities. Your use of an 'exit' menu option is non-standard (not to say it is bad).
One option would be to do the backing out through your activities yourself. Perhaps now you are just finishing the current activity and you should instead finish all the activities in the back stack.
Another option is that you could save a flag, and when the UI is launched again you could read that flag and launch the appropriate activity (but again be careful with the backstack). The easiest way to set that flag is probably by overriding onSaveInstanceState(Bundle) and then reading the bundle in onCreate (or use sharedpreferences).

Have you tried setting the clearTaskOnLaunch to true for your main activity (in your manifest).
From the documentation:
When the value is "true", every time users start the task again, they are brought to its root activity regardless of what they were last doing in the task and regardless of whether they used the Back or Home button to leave it.
This seems to describe what you want to do. I have never tried this personally, but it seems worth investigating for your purpose.

Finish leaves activity in stack

I have an activity that performs a small bit of code and then calls finish. This works fine and the activity goes away, but if I press the history button (if it's called the history button?) the activity still appears to be there, though clicking it will do nothing.
I have enabled android:noHistory="true" in my manifest. I only have a single activity that changes some settings, and then calls finish, nothing else.
Is there a way for me to make that trace of the activity go away?

Assuming that the history button you refer to is the list of recent apps, you can set
android:excludeFromRecents="true"
By default value for this attribute is false.
For other attributes check the link: http://developer.android.com/guide/topics/manifest/activity-element.html

Home button and back to app in a newly installed app loads the initial activity again

I'm encountering the following scenario in my application:
Installing it and immediately opening it (using the open button
after the installation, instead of the icon in the applications
list).
Navigating through a few activities.
Clicking the home button.
Clicking the application icon to load it again.
Instead of returning to the activity I was in, the initial activity
is loaded. The previous activity is still there and can be accessed by clicking the back button, but there isn't really a way to know that and it looks like the app was completely restarted.
This may be an issue in this app, because in some cases it might require a registration after performing a few actions, and losing the focus on the activity could be very annoying
Is there anything that can be done to avoid that?

There's a couple of flags under Intent that might be helpful. You use them when an Activity is launched:
"FLAG_ACTIVITY_TASK_ON_HOME: If set in an Intent passed to Context.startActivity(), this flag will cause a newly launching task to be placed on top of the current home activity task (if there is one).
FLAG_ACTIVITY_REORDER_TO_FRONT: If set in an Intent passed to Context.startActivity(), this flag will cause the launched activity to be brought to the front of its task's history stack if it is already running."
http://developer.android.com/reference/android/content/Intent.html

How to return to the same activity instance after resuming it?

The problem is somewhat odd and after having trying to figure it out for about a day now, I am posting it here.
I have an application where an activity A(main activity) launches other activities(B,C or D).
The issue here happens when activity A has started Activity B and 'home' button is pressed.
Case 1 - When I test my application in debug mode on my device (HTC Desire) after pressing the 'home' button, I again click the application icon, it returns to the same activity (activity B), which is what is should do. No issues here.
Case 2 - When I export the signed package, and then install the application on the same device, then if I click the application icon after pressing the 'home' button, then a new instance of activity A (main activity) is launched ON TOP of activity B. I got to know this because when I press 'back' from that activity, it returns to activity B and pressing 'back' again shown activity A.
The behavior ceases to exist if the application is quit in the same order it was started, that is, if I press 'back' from activity B, then 'back' from activity A (exit).
After this everything runs fine.
I have tested it many times with different settings but I can't seem to figure out why the behavior is like this.
Any help is appreciated.

I think giving Activity A the 'single top' flag in your manifest should fix this.

Regarding Case 1:
When launching your intent from Activity A to start Activity B, add the flag FLAG_ACTIVITY_CLEAR_WHEN_TASK_RESET
This will ensure that when you go home and launch the the app again, Activity A will be shown.
Regarding Case 2:
I'm not exactly sure how this would occur. It seems like it thinks you have two versions of the app, the signed one and the unsigned one but keeps them both in the same task stack. You may want to consider using singleTask or singleInstance for your Activity if you only want one instance. See the doc on tasks and back stack for more details.

I would agree with Noel regarding the likely cause of Case 2. Without task reparenting or it being set to a launchmode preventing multiple instances of an activity, there is a chance that launching it from Home isn't deemed the same stack as launching it from Eclipse (assuming this to be the case).
In my talent calculator app I have the whole application set allowTaskReparenting=true to ensure nothing is left in other stacks (primarily email as it can email launch urls). I then have my main activity set to launchMode="singleTask" as I only ever want one instance of this to exist no matter what launches it or with whatever intent.
My only other activity is for loading and saving and that has noHistory="true" to make sure it is removed and never returned to. That basically means it only exists while you're in it, and can never return to it.
clearTaskOnLaunch="true" will also ensure only the main Activity remains in the stack when it's launched from Home, but this isn't always the case if you have other ways to get into your activity. If it's only ever launched from Home then set this.
Hope that all helps.

Do you start you application manually or using Eclipse or another IDE? When starting from Intellij IDEA I had exactly the same problems. Then I stopped and ran it manually and behaviour was as expected.

Weird Home button behavior

I'm experiencing kind of strange behavior of my application after hard Home button is pressed.
When you press Home, everything is OK - my app goes to the background, showing Home screen. But if you try to choose my app in the main menu or in the list of last tasks it behaves like it was not started before and does not show the last activity you were on - it just starts from scratch, namely, shows the splash screen and starts next corresponding activities. Moreover, old activities of this app remain on the activities stack, and previous instance of the app is not terminated - so if you press Back for a few times you'll just run into those activities which were undoubtedly started during the previous session of work with my app. Splash screen activity is filtered by "android.intent.action.MAIN" filter and "android.intent.category.LAUNCHER" category.
The strange thing is that all of that happens despite the fact that I do not intercept any Back key hits, or override any onPause or onResume methods. What's happening contradicts with my understanding of Android app lifecycle - I was sure that when you hit Home an app just goes to the background, and when you choose it in the menu later - it just unwinds and does not start anew. (Of course, unless stuff like that is stated in the app manifest or corresponding methods are overridden or something else).
I also checked it for some other lifecycle events - such as changing orientation or flipping hard keyboard out - and none of those led to such strange results. It appears that the problem occurs when you try to start the app from main menu or menu of last applications.
I hope you will be able to help me. Any advice on what to pay attention to or where to search for solution would be really great.
Regards, Alex

You need to set android:launchMode="singleTask" in your LAUNCHER activity in your manifest file.
For more info on the launchMode attribute see here
Note that:
The default mode is "standard".
and:
Every
time there's new intent for a
"standard" activity, a new instance of
the class is created to respond to
that intent.