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I upgraded my iPhone 3GS to iOS4 and although I love most of the new feaures, multitasking keeps me checking for open apps.

Is there a way to disable multitasking support in iOS4 or a "kill all apps" app/switch?

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Can you clarify what you mean by "multitasking keeps me checking for open apps"? Are you worried about performance or battery life, and tired of trying to make sure nothing needless is running? Or is there some kind of background app that is specifically bothering you? –  Anonymous Jul 14 '10 at 20:50
    
If it's not the battery life for him, it is that for most of us. –  Cawas Jan 4 '11 at 17:21
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5 Answers 5

You may be worrying more than you need to be. Apps can only use multitasking for certain functions:

  • Playing audio
  • Tracking your location
  • VOIP
  • Local notifications and alerts
  • Complete a lengthy operation

In all cases, rather than the app remaining running, the system keeps it suspended and awakens it at appropriate times, such as when it needs to fetch more audio. If the app uses too much CPU while it's in the background, it gets terminated. If the foreground app needs more memory, then the background apps will get terminated as necessary.

The apps in the multitasking menu aren't necessarily consuming any resources or battery life, it's more like a "most recently used" list. Apps will still be listed there whether or not they are actually running. You can help prove this to yourself by turning the phone off and on; the recent list will still be populated even though obviously all the apps are terminated.

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This is mostly true. However, I got a "low memory" warning when trying to play Rock Band on my iPhone 4 that would only disappear once I manually quit all the apps I had open. –  Kyle Cronin Jul 15 '10 at 5:27
    
So install a taskkiller @Kyle, but don't go blaming faulty programming on multitasking ;-) It's a bug of the power draining apps, not the OS –  Ivo Flipse Jul 24 '10 at 8:16
    
I have to agree with @Kyle here, I won't blame multitasking but fact is some apps are just badly developed, If only Apple had foreseen this and given us a kill all button. Clearly they don't have enough manpower to do memory leak analysis on all apps. –  Mikeware Jul 27 '10 at 16:39
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With most apps, there's indeed no problem. I've noticed, however, that some apps like Skype definitely drain battery way too fast if you leave them on the background. –  Jonik Nov 9 '10 at 15:21
    
@Kyle There is no such thing as iOS "Low Memory" warnings, at least nothing a user can see. When an app like Rock Band displays a warning, it means that Rock Band is trying to use too much memory. Any backgrounded apps will be killed if they use enough memory to affect performance. –  kubi Nov 9 '10 at 22:03
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One way to control multitasking on iOS4 is to jailbreak your device, install Backgrounder, and install Remove Recents.

  • Using Backgrounder you can prevent apps from multitasking until you allow them.
  • Using Remove Recents will clear out all the "recently used" apps so that only the apps that are actually multitasking are shown.

Completely disabling multitasking is also possible. Here's how to disable Multitasking, Homescreen Wallpaper, or both on a 3GS. A jailbroken device is required.

Edit the file N88AP.plist in the directory /System/Library/CoreServices/SpringBoard.app on your iPhone. Look for the following key-value pairs and set them to false as shown. Reboot when complete.

<key>homescreen-wallpaper</key>
<false/>

<key>multitasking</key>
<false/>

I figured this out by reading this article about enabling Homescreen Wallpaper on a 3G, although I did the opposite.
http://pixelatedgeek.com/2010/06/ios4-jailbreak-and-multitasking-now-available-for-iphone-3g/

Note:
You will need a way to edit plist files. Either use a special plist editor, or use a tool to convert to XML. To do the conversion on your phone, install Ericia Utilities (from Cydia) and issue the following commands to convert the file to XML and back.

plutil -convert xml1 N88AP.plist
plutil -convert binary1 N88AP.plist
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I believe it's an option when you jailbreak using redsn0w. It's an option. Here's a tutorial.

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There is no close all option as far as I'm aware, but you can close them one by one:

"Double-tap the home button to bring up the multitasking bar, which pops up from the bottom of the home screen. Then, you simply scroll through the icons, find the one you wish to close, press and hold the icon, and then click the red circle with a dash--Apple's visual representation of a delete symbol." - Via PCWorld.com

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There is a close all button if you install sbsettings, it's called Remove Background. It's a button which closes all the apps and clears the "Recently Used" dock.

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