Re: How to close background apps? [UPDATE]
[UPDATE]you can close any app by double pressing the back button while it is active.
I don't believe that this is true. Apps quit when users back out of the app's initial page. A tap of the back button moves back a page; a double-tap of the back key is treated as two single taps. If an app were showing its second page, a double-tap would quit, but an app showing it's third page wouldn't and an app showing its first would quit, reactivate the previous app, then back up one page there.
As has been said many times on these boards, there is no "systems" need to quit an app. The only need to quit an app is to change what shows when users do a long press of the back key or what gets brought to the screen when users tap the back key. With few exceptions for specific function calls, third-party apps in Windows Phone do not do anything unless they are on-screen. The term "background" tasks is bad because sometimes it's said to mean "I didn't quit the app and it's off-screen, therefore it's in the background" while at other times it may refer to the "Background Tasks" page in the Settings. Here's a quick summary:
App Type
| Uses processor
| Uses memory
|
On-screen
| Yes
| Yes
|
Microsoft (phone,
IE?, maybe others)
| Yes
| Yes
|
Off-screen
| No, except for
special APIs
| Yes, unless
OS needs it
|
Periodic Tasks (aka
Background Tasks)
| Up to 25 sec
every 30 min
| 6 MB limit
|
What some users call "background" apps are often simply suspended, off-screen apps that use no CPU and run the risk of being unloaded from memory if the operating system needs the memory for another purpose.
The apps listed in the Background Tasks page in Settings is a list of apps that come with specially-written and very small "applets" that users
may allow to run for up to 25 seconds every half hour. It is important to know that the thing that is run on that schedule is
not the same thing that runs when users tap the app's icon or tile -- it is a tiny subset of the whole app; it likely grabs some data over the cellular network, stores it locally, and maybe updates some tiles. The OS will automatically kill such a periodic task if it exceeds 6 MB or 25 seconds of run time. Further, if the OS has to kill it twice in a row, the OS "deschedules" it so that it doesn't get to make a third try.
So, with the exception of some special off-screen APIs (like for navigation, streaming audio, etc) and for some Microsoft-provided apps, not much CPU is being consumed except by the user turning on the screen and doing something.