iPhone multitasking explanation

[iluvifone]

I was on another site and read this:

"I hate apple's fake multitasking process and prefer backgrounder even if it uses more battery. But hey it's true multitasking."


Sorry for being a noob, but I just got the iPhone 4 a few months ago, and it does "multitasking" as to what I expected it to do (such as remaining signed in to chat with eBuddy, iPod playing in the background, games resuming where they left off, etc).

What exactly are they referring to, that the iPhone doesn't natively do?

I would like to be enlightened to more features

 

[grapes911]

iOS generally doesn't run apps in the background. There are a few exceptions, but generally it saves the state of the application in memory when you exit the app. When you need it, it opens it up and it's ready to go. Personally, it's better this way.


Check out this article by chpwn. If you are not familiar with him, he has written many jailbroken apps for the iPhone, including ProSwitcher.

 

[mpossoff]

I've haven't figured out what the purpose of the multi task mode(double clicking home) myself.

As an example if the iPod app is in multi task mode, how does this app play into it?

Marc

 

[mpossoff]

I understand that real multi tasking is not good for battery life.

Honestly I think the so called multi tasking on the iPhone is a waste unless someone can help to utilize it with whatever potential it has.

Marc

 

[Zcott]

Good multitasking shouldn't be noticeable, meaning it shouldn't drain the battery and shouldn't clog up the system. iOS does neither of these things, so it works for all my uses.

I used "real" multitasking on Windows Mobile a few years ago and it was awful. Having to start task manager and close apps all the time was a real nuisance.

 

[grapes911]

Honestly I think the so called multi tasking on the iPhone is a waste unless someone can help to utilize it with whatever potential it has.

It's extremely useful for me. I love being able to close my RSS, Twitter, or whatever else and open it up from where I left off. I love being able to stream Pandora in the background while I do other things.

You can't say it's a waste without any information to back that up. How are you using it? What are you trying to do that you can't?

 

[Saberon]

Here's a rundown


First, an app has to be updated to use MT. This is called fast-app-switching and it means that if I switch to another app, I can resume my place in the old app.

Example: Playing a game, go to check mail, I can go right back to where I was in game without restarting the game.

The only time an app actually runs in the background is when it has GPS/VOIP/Background audio.

Example: Skype can receive calls while its in the background. Pandora can play music even though the app isn't open on your screen/NAVIGON can give you turning directions while you're in another app.

The double click home button is supposedly a faster way of getting back and forth between apps although that is debatable whether its faster vs homescreen.


If it was TRUE multitasking, when I switch from the game to mail, the game would still be running and using CPU/Memory while I am in mail. It is not frozen, but keeps on running as if I was playing it. This is what causes the drain/performance.

 

[mpossoff]

It's extremely useful for me. I love being able to close my RSS, Twitter, or whatever else and open it up from where I left off. I love being able to stream Pandora in the background while I do other things.

You can't say it's a waste without any information to back that up. How are you using it? What are you trying to do that you can't?

Couldn't that be done without double clicking home?

I mean double click home seems like last used app to me?

Marc

 

[iluvifone]

Here's a rundown


First, an app has to be updated to use MT. This is called fast-app-switching and it means that if I switch to another app, I can resume my place in the old app.

Example: Playing a game, go to check mail, I can go right back to where I was in game without restarting the game.

The only time an app actually runs in the background is when it has GPS/VOIP/Background audio.

Example: Skype can receive calls while its in the background. Pandora can play music even though the app isn't open on your screen/NAVIGON can give you turning directions while you're in another app.

The double click home button is supposedly a faster way of getting back and forth between apps although that is debatable whether its faster vs homescreen.


If it was TRUE multitasking, when I switch from the game to mail, the game would still be running and using CPU/Memory while I am in mail. It is not frozen, but keeps on running as if I was playing it. This is what causes the drain/performance.

That's the closest to a response I have gotten so far, Thank you.

I'm still confused, like.. what exactly entices people to use 'backgrounder' or w/e from cydia instead of the regular double-tapping multitasking (i can understand that some apps haven't been updated for MT, but most have..)? All the apps that i've minimized and came back to have worked fine, but why the big fuss?

 

[grapes911]

Couldn't that be done without double clicking home?
I mean double click home seems like last used app to me?

Double clicking the home button is the last used apps. You can click the home button one, go back to the home screen, and then open a new app. You'd still get multitasking. You need to separate double clicking the home button from multitasking. They are not the same thing.

I'm still confused, like.. what exactly entices people to use 'backgrounder' or w/e from cydia instead of the regular double-tapping multitasking

Some people like their apps to actually run in the background. I'm not sure why, but they do. You really should read the link I posted above. It has a lot of good information about whats actually happening.

 

[Saberon]

Also, the double click home bar really doesn't have anything to do with MT. It's a list of apps you've used most recently. Even if an app doesnt support MT, it will still show up there.

Honestly, I don't know what the big rave about backgrounder etc on Cydia is about. I know people do it a lot with their iPad's because its the only way to get any sort of MT on iPad at this point.

 

[mpossoff]

Double clicking the home button is the last used apps. You can click the home button one, go back to the home screen, and then open a new app. You'd still get multitasking.

Right that's what I do. When I want to go to the app I was using I just go to the app without double clicking home.

I'm not referring to iOS multi tasking as I said I'm referring to the mode(double clicking home).

Marc

 

[Compile 'em all]

I've haven't figured out what the purpose of the multi task mode(double clicking home) myself.

As an example if the iPod app is in multi task mode, how does this app play into it?

Marc

The switcher at the bottom has nothing to do with multitasking or backgrounding. The switcher at the bottom is for recently opened apps. All apps in that bar are suspended and aren't actually running unless they explicitly implement one of the 7 services that can run in the background.

 

[grapes911]

I'm not referring to iOS multi tasking as I said I'm referring to the mode(double clicking home).

Then I think you are in the wrong thread. The topic is about multitasking, not about the recently used apps. They are not really the same thing.

 

[SnowLeopard2008]

Apple's implementation is not "fake" but different than true multitasking (i.e. like a computer). There are pros and cons to true multitasking on mobile devices. However, Apple's approach compliments battery life whereas true multitasking would drain it quickly. It's not perfect, but battery performance is very important on a mobile device. It's not like computers, where desktops have *infinite* power sources and laptops aren't used away from a power source 100% of the time.

 

[iluvifone]

You really should read the link I posted above. It has a lot of good information about whats actually happening.

I just did. I guess it sort-of makes sense now. Some people just want 'real multitasking' just for the heck of it, with no real pro's, just one big con- battery wasting.

I can justify multitasking on a desktop, because say, for example, you were editing a photo on photoshop, and then get a IM from MSN, for example. Imagine if once you went to reply to the conversation with your friend, you were forced to launch photoshop and start all over again. That is, in essence, what we had to do prior to iOS 4, but now, from what I'm getting, the app is in a "frozen" mode, until called upon again. Perfect! Again, Why anyone would want otherwise is beyond me, I've yet to see a valid reason to why
backgrounder > iOS multitasking

 

[grapes911]

It sounds like you now understand. Good!

Again, Why anyone would want otherwise is beyond me, I've yet to see a valid reason to why
backgrounder > iOS multitasking

The only think I can think of is that the original iPhone and the 3G don't support multitasking via Apple. They still need Backgrounder. Other than that, I have no idea why you'd want it.

 

[Zcott]

I just did. I guess it sort-of makes sense now. Some people just want 'real multitasking' just for the heck of it, with no real pro's, just one big con- battery wasting.
(snip)
Again, Why anyone would want otherwise is beyond me, I've yet to see a valid reason to why
backgrounder > iOS multitasking

Haters gonna hate. On principle.

 

[JulianL]

I struggle to understand the reasoning of people who criticise Apple for not having full multitasking. What on earth do you want it for on a handheld device?

Here's an example of what you could do if iOS had full multitasking. You could create very complex spreadsheet models that took maybe 10 minutes to calculate a value. With iOS as it is now you would need to set the spreadsheet model running but as soon as you switched away from it the calculation would be suspended. At least the state would be saved (if the spreadsheet app is written properly for iOS 4) so when you switch back to it it will carry on where it left off but ultimately you will need to have the spreadsheet app on screen for 10 minutes and sit staring at it waiting for it to finish. If iOS had full multitasking then you could start the calculation, switch to another app, and the spreadsheet app would carry on running the calculation in the background. The problem is that while it is running it is taking CPU cycles so whatever you do with whatever foreground app you are running could become sluggish and since the CPU will be running flat out then if you had an error in the spreadsheet that meant the calculation went into a loop and never stopped then it would keep running until either you switched back to the spreadsheet and realised that something was wrong or else the CPU kept running flat out on the broken calculation until it drained the battery.

I used a spreadsheet calculation as an example but you could substitute any computationally intensive activity that doesn't require user interaction, e.g. compressing data (zip), converting audio or video files from one format to another or trying to crack the encryption on an encrypted file. This really isn't the sort of stuff that most people really need to do on a handheld device and the consequences if the calculation goes wrong in the background (gets stuck in a loop) are unpleasant.

I think Apple have judged their implementation of multitasking very well. In general an app is put into suspended animation when it is no longer in the foreground but can ask iOS to do certain restricted things on its behalf while it is asleep, e.g. a chat client listen for new messages, a file app complete a download or a radio app continue to stream audio data to the audio circuitry.

- Julian

 

[Daveoc64]

A very simple example of why iOS's multitasking is poor is IM.

When you close an IM App (like Windows Live Messenger or Palringo), the app disconnects from the service(s) it is connected to and switches to using push notifications to continue receiving messages.

When you get a new message, the messaging service (like AIM or Windows Live Messenger) has to forward that message through Apple's push notification service, which relays it to the phone.

That takes additional time and is often unreliable. In many cases there will be an additional server in between (run by the App developer) which adds further unreliability and delay.

When you get a notification from an IM service and you press the button that notification provides to open the App, that App must then open up again and connect to the IM service. Once it has done that, it must download any messages that have been received since the App was last open.

IMO all of this is unnecessarily complex for something that is just sending and receiving text.

 

[Daveoc64]

I struggle to understand the reasoning of people who criticise Apple for not having full multitasking. What on earth do you want it for on a handheld device?

Here's an example of what you could do if iOS had full multitasking. You could create very complex spreadsheet models that took maybe 10 minutes to calculate a value. With iOS as it is now you would need to set the spreadsheet model running but as soon as you switched away from it the calculation would be suspended. At least the state would be saved (if the spreadsheet app is written properly for iOS 4) so when you switch back to it it will carry on where it left off but ultimately you will need to have the spreadsheet app on screen for 10 minutes and sit staring at it waiting for it to finish. If iOS had full multitasking then you could start the calculation, switch to another app, and the spreadsheet app would carry on running the calculation in the background. The problem is that while it is running it is taking CPU cycles so whatever you do with whatever foreground app you are running could become sluggish and since the CPU will be running flat out then if you had an error in the spreadsheet that meant the calculation went into a loop and never stopped then it would keep running until either you switched back to the spreadsheet and realised that something was wrong or else the CPU kept running flat out on the broken calculation until it drained the battery.

I used a spreadsheet calculation as an example but you could substitute any computationally intensive activity that doesn't require user interaction, e.g. compressing data (zip), converting audio or video files from one format to another or trying to crack the encryption on an encrypted file. This really isn't the sort of stuff that most people really need to do on a handheld device and the consequences if the calculation goes wrong in the background (gets stuck in a loop) are unpleasant.

Your example doesn't work because you don't understand the iOS 4 Multitasking APIs.

Apps can do anything for up to 10 minutes in the background. Apple intended the API to be used for things like finishing off the sending of an email or continuing to download new data in the background, but many developers are using it to get as close to proper multitasking as possible.

You seem to think that these tasks don't need to happen or that people don't want to use them, when the reality is that millions of people have been using them since June.

I think Apple have judged their implementation of multitasking very well. In general an app is put into suspended animation when it is no longer in the foreground but can ask iOS to do certain restricted things on its behalf while it is asleep, e.g. a chat client listen for new messages, a file app complete a download or a radio app continue to stream audio data to the audio circuitry.

Apps can only do one of the things you list (audio - and it doesn't work how you think).

 

[iluvifone]

A very simple example of why iOS's multitasking is poor is IM.

When you close an IM App (like Windows Live Messenger or Palringo), the app disconnects from the service(s) it is connected to and switches to using push notifications to continue receiving messages.

When you get a new message, the messaging service (like AIM or Windows Live Messenger) has to forward that message through Apple's push notification service, which relays it to the phone.

That takes additional time and is often unreliable. In many cases there will be an additional server in between (run by the App developer) which adds further unreliability and delay.

When you get a notification from an IM service and you press the button that notification provides to open the App, that App must then open up again and connect to the IM service. Once it has done that, it must download any messages that have been received since the App was last open.

IMO all of this is unnecessarily complex for something that is just sending and receiving text.

That was a perfect answer, thank you. From first-hand experience, I recall when getting a new notification from eBuddy, and opening the app via the push notification that Apple sends, it takes a couple of seconds to download the stuff from the server.

Thanks again!

 

[JulianL]

Your example doesn't work because you don't understand the iOS 4 Multitasking APIs.

Apps can do anything for up to 10 minutes in the background. Apple intended the API to be used for things like finishing off the sending of an email or continuing to download new data in the background, but many developers are using it to get as close to proper multitasking as possible.

You seem to think that these tasks don't need to happen or that people don't want to use them, when the reality is that millions of people have been using them since June.



Apps can only do one of the things you list (audio - and it doesn't work how you think).

OK. Thanks for the clarification. I'm a computer scientist and have worked on Unix kernel development (amongst other things) but I've never worked with the iOS APIs so I appreciate the correction. Surely the 10 minute limit still protects against my runaway app scenario though doesn't it (?), so I still hold my opinion that Apple's implementation is well judged. What happens after 10 minutes? Is some app-defined error handler called? What options to save state is the app given at this point?

Doesn't your final statement "Apps can only do one of the things you list" contradict one of your initial statements "Apps can do anything for up to 10 minutes in the background"? I'm not picking an argument, just trying to understand.

- Julian

 

[brendu]

true multitasking does not have to kill battery life or cause performance problems or require an android style task killer. Palm has the most effective and simple way to truly "multitask". But since no one cares about Palm anymore iOS has the 2nd best solution. It is simple, effective, and in many cases works as well as Palms cards system.

If any of you have ever used webOS you know what I am talking about, if you havent, dont bash palm for sucking.

 

[Timeraner]

Wirelessly posted (Opera/9.50 (Nintendo DSi; Opera/507; U; en-US))

Home double-click is perfect for my situation, because of what it does. My iPod touch 2G works fine with multitasking. Every now and again it slows, so I double-click home, then hold down the app icons I don't want multitasking and click the - minus.