I am recording output from a accelerometer.
Can anyone recommend a reliable way to monitor
onSensorChanged after the app has been closed (running the app in the background).
I have experimented with
WorkManager appears to run only when the app is open. I read that this may be device specific as some devices force stop the app on close or otherwise prevent background tasks from executing once the app is closed.
I am curious about using
sticky-notifications, although this would not be my first choice. I am now researching this option. I have noticed a few apps which implement this option. The downside is the sticky-notification can be viewed as annoying and the user may disable
WorkManager is not the right solution in this case as a Worker has an execution limit of 10 minutes, then it’s stopped by the OS. But, time limit aside, WorkManager has been developed for other use case, so using for something like this (using some hack to reschedule a worker when you’re close to the 10 minutes limit) seems a fight against the library design. To have an introduction behind the use cases that WorkManager is designed to solve you can take a look at this blog: Introducing WorkManager.
A Foreground service is an option, but I’m afraid that continuously monitoring the sensor can have a very bad impact on the battery life of the device. For more information on the available options, to run code in the background, your can check this blog: Modern background execution in Android
An alternative, depending on what you need to do with the sensor data, is to use the Activity Recognition API:
You can tell the API how to deliver results by using a PendingIntent, which removes the need to have a service constantly running in the background for activity detection purposes. Your app receives the corresponding Intents from the API, extracts the detected activities, and decides if it should take an action.
March 2021 Update
There have been a couple of updates since I originally wrote this answer:
- WorkManager v2.3.0 introduced support for longer Workers with the option to “promote” them to Foreground Services using
] for all kind ofWorker`s. This is allows to overcome the 10 minutes limit and is documented in Support for long-running workers.
- Android 12 is planning to introduce some changes to Foreground Services and this has some impact on WorkManager. The new v2.7.0, currently in alpha, is adding the concept of expedite work to provide support for Android 12 in a backward compatible way.
Overall, I still think that having your app monitoring the sensors while in background is going to have a bad impact on the battery of the device and you should look for alternatives.