如何使用新的架构组件在android中跟踪当前位置？

Question

I have a project, in which I have successfully implemented location tracking feature, and is working perfectly. I am tracking users current location using fused location provider in every 30 seconds.(tracking starts when MainActivity started).

Now I am planning to update that project with newly introduced android architecture components. But I don't know how to implement location tracking with view model.Where is the right place to start location tracking, in MainActivity or Application class? Should I use ViewModel or AndroidViewModel ? How to achieve this.

Answer 1

The correct way would be to have a TrackingRepository where you do all calculations in a background thread of the device location. Create a MutableLiveData where you will assign the location. Then update its value using postValue() or setValue() . Write a public getter for this MutableLiveData . This repository will be your location API.

Then your ViewModel should call the method of your repository and assign its result to a LiveData variable of the ViewModel . Then in your Fragment/Activity observe the liveData of your ViewModel . Just as the Guide to App Architecture does.

Remember to use dependency injection which really helps with the new architecture.

Answer 2

After few hours of try, finally I could find the solution.

First create a variable inside the LocationRepository.

val currentLocation = MutableLiveData<Location>()

Inside the LocationCallBack (onLocationResult)

currentLocation.postValue(locationResult.lastLocation)

Thereafter in the ViewModel class again

val currentLocation = MutableLiveData<Location>()

and

fun currentLocation(): MutableLiveData<Location>
{
    currentLocation = myLocationProvider.currentLocation
    return currentLocation
}

at least you have observe the ViewModel's MutableLiveDate in your Activity/Fragment

myLocationProvider.currentLocation.observe(this, Observer { currentLocation ->
            currentLocation?.let {
                //Your code here
            }
})

EDIT You have to start the the LocationCallback with suspendCoroutine, GlobalScope and UiDispatcher.