Why dont Android applications provide an "Exit" option?

Question

Is there something in the Android developer guidelines that disuades developers from providing the option to "exit" (stop running) an application from within the application itself?

I love multitasking and all but it's not clear to me why:

• the vast majority of apps don't have their own Exit functions and hence just keep running forever
• don't give you a choice about running when you turn on the phone - they just do by default

Both of these things lead to memory usage constantly increasing and your device running with this performance burden all of the time despite the fact that you may only want certain apps to run some of the time.

Am I missing something?

Answer 1

Is there something in the Android developer guidelines that disuadea developers from providing the option to "exit" (stop running) an application from within the application itself?

Yes. It is generally not needed, just as it is generally not needed to restart a Web server because some user with a browser decided (s)he is done with a Web app.

the vast majority of apps don't have their own Exit functions and hence just keep running forever

They don't keep running forever. Android will close things up as needed.

don't give you a choice about running when you turn on the phone - they just do by default

Those developers aren't paying attention to me.

Both of these things lead to memory usage constantly increasing

Generally, it doesn't. If you find specific apps that do this, uninstall them.

and your device running with this performance burden all of the time

Generally, it doesn't. If you find specific apps that do this, uninstall them.

Also, this question is a duplicate of this one.

Answer 2

Essentially, there's no need for a quit button as long as the developer does a good job of designing their app. Android activities are stopped when they aren't visible and resources are needed elsewhere, so the are no longer consuming resources. You can read about the lifecycle here:

Here's a related question:

Answer 3

"Both of these things lead to memory usage constantly increasing"

Which doesn't matter since Android apps are limited to a fixed amount of RAM. Freeing RAM won't give more RAM to other apps.

Answer 4

From Google's Android Application Fundamentals page:

Shutting down components A content provider is active only while it's responding to a request from a ContentResolver. And a broadcast receiver is active only while it's responding to a broadcast message. So there's no need to explicitly shut down these components.

Activities, on the other hand, provide the user interface. They're in a long-running conversation with the user and may remain active, even when idle, as long as the conversation continues. Similarly, services may also remain running for a long time. So Android has methods to shut down activities and services in an orderly way:

An activity can be shut down by calling its finish() method. One activity can shut down another activity (one it started with startActivityForResult()) by calling finishActivity(). A service can be stopped by calling its stopSelf() method, or by calling Context.stopService(). Components might also be shut down by the system when they are no longer being used or when Android must reclaim memory for more active components. A later section, Component Lifecycles, discusses this possibility and its ramifications in more detail.

So it seems like Content Providers and Broadcast receivers should never be explicitly shut down, as they are inert while not handling their specific events.

As for Activities, I would argue in favor of having an end to it, but in certain cases. If your app has a finite state in which the user is done using it, why keep it alive until GC gets it? The activity manager still needs to keep track of that Activity while the user has finished their task. My best example for this is the Calculator. You open it, you have it solve a problem for you, and then you close it. If the onCreate function is so expensive that it's more effective to do onCreate once and then onRestart whenever the user moseys back to your application then you're probably doing something wrong. Maybe I'm misinterpreting how Android handles Activities, and if so I'm always interested in learning more :)