Extremely slow updates / fps when in background mode

[StephenCathcart]

Hi,

I'm writing my first mobile app using Ionic which gathers motion and gyroscope data to track movement once every 50ms. This needs to work when the user has their phone locked, hence I'm using the background mode plugin.

I'm noticing that the interval time between capturing data increases significantly when running in the background (while the phone is locked), and capturing data every 1 second rather than every 50ms.

To keep things simple, I placed a setInterval function to tick every 20ms in the constructor of a new app and to just print out Date.now(), output:

1526419240971
1526419240991
1526419241011
1526419241031   <---- Locked phone here
1526419242031
1526419243032
1526419244031
1526419245031
1526419246031

Is there anything that can be done to keep the app ticking as quickly as when it's in focus? Is this a limitation with Hybrid frameworks and would a native app be able to handle this?

Thanks

[StephenCathcart]

This issue can be closed and my solution to the problem can be found here:

dorukeker/gyronorm.js#52

To summarize, browsers throttle timers (such as setInterval) to only fire once per second when out of focus (inactive tab). The hacktimer.js library can be used to prevent this.

In order for the application to continue functioning at full speed on iOS when the user has locked their phone, the following config needs to be placed inside of config.xml:

<platform name="ios">
    // other stuff
    <config-file parent="UIApplicationExitsOnSuspend" target="*-Info.plist">
        <true />
    </config-file>
</platform>

Cheers