Core Motion in the background?

Will Core Motion fr开发者_开发技巧amework work while the app is in the background?

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The Core Motion framework allows access to historical data for CMPedometer data, so if your app is only using this there is no need to run in the background.

I have been playing around with CM the last week and in my testing if you have an active query running when your app is sent to the background, the query handler receives a flood of events (that occurred while the app was suspended) upon returning to the foreground. I don't know how many events will be cached, and I haven't seen anything in the docs about this.

This behaviour seems to be sufficient. I can't think of a use case for Core Motion where you need constant background access, historical CMPedometer data doesn't suffice, and fits within the App Store guidelines.

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Depends on your definition of working... Will Core Animation need to continue running or are you expecting the view to be frozen? When an app runs in the background only certain processes are allowed to run. (Notifications for example).

For the most part the application UI, and by extension is paused until you trigger applicationDidBecomeActive. Once that starts up again it should resume, but again not continue running in the background. Same can be said for most games on iOS running OpenGL, it's paused until the app is active again.

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one of the apps- moves that is used to track your walking steps is quite amazing, because even you make it into background or killed, it can indicate the steps you walked. So some internal mechanism of gyroscope and GPS and other sensors can carry on when the apps are killed.

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In order to let your app run in the background, you have to declare it as a background task. The problem is that there are only a few UIBackgroundModes ... and motion isn't one of it.

A workaround could be to enable the UIBackgroundMode location, which is intended to let users know about their location even if the app is in the background. You could then wrap your motion logic within. Nevertheless, the clear drawback of this is that it involves usage of the GPS, which will drain the battery significantly...