As an example, I'm using FusedLocationProviderClient to access the current location, which returns a task which callback will eventually return the location. The method looks something like follows:
fun getLocation(callback: MyCallback){
val flpc = LocationServices.getFusedLocationProviderClient(it)
flpc.lastLocation.addOnSuccessListener {
callback.onLocation(it)
}
}
Is it possible to transform this so that I can use corroutines to suspend this function and wait for the task returned by flpc.lastLocation
so I can return it in this method and this way get rid of that callback? For example something like this:
suspend fun getLocation(): Location? =
withContext(Dispachers.IO){
val flpc = LocationServices.getFusedLocationProviderClient(it)
return@withContext flpc.lastLocation.result()
}
My question is if there is something around coroutines where I can return the result of a Task
(in this example, a Task<Location>
)
Thanks in advance!
The kotlinx-coroutines-play-services
library has a Task<T>.await(): T
helper.
import kotlinx.coroutines.tasks.await
suspend fun getLocation(): Location? =
LocationServices.getFusedLocationProviderClient(context).lastLocation.await()
Alternatively take a look at Blocking Tasks
It would be used the next way:
suspend fun getLocation(): Location? =
withContext(Dispachers.IO){
val flpc = LocationServices.getFusedLocationProviderClient(context)
try{
return@withContext Tasks.await(flpc.lastLocation)
catch(ex: Exception){
ex.printStackTrace()
}
return@withContext null
}
Just to add to this example, for completion purposes, the call to getLocation()
would be done the next way:
coroutineScope.launch(Dispatchers.Main) {
val location = LocationReceiver.getLocation(context)
...
}
However this negates the benefits of coroutines by not leveraging the available callback and blocking a thread on the IO dispatcher and should not be used if the alternative is available.
Another way that I have don this that can also be used with any callback type interface is to use suspendCoroutine<T> {}
.
So for this example it would be:
suspend fun getLocation(): Location? {
return suspendCoroutine<Location?> { continuation ->
val flpc = LocationServices.getFusedLocationProviderClient(it)
flpc.lastLocation.addOnSuccessListener { location ->
continuation.resume(location)
}
// you should add error listener and call 'continuation.resume(null)'
// or 'continuation.resumeWith(Result.failure(exception))'
}
}
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