feat: use FusedLocationClient for google flavor

app/build.gradle

@@ -205,6 +205,9 @@ dependencies {
     // implementation 'com.google.android.things:androidthings:1.0'
     implementation 'com.github.mik3y:usb-serial-for-android:3.4.6'
 
+    // location services
+    googleImplementation 'com.google.android.gms:play-services-location:19.0.1'
+
     // For Firebase Crashlytics & Analytics
     googleImplementation 'com.google.firebase:firebase-crashlytics:18.2.6'
     googleImplementation 'com.google.firebase:firebase-analytics:20.1.0'

app/src/google/java/com/geeksville/mesh/repository/location/SharedLocationManager.kt

@@ -0,0 +1,87 @@
+package com.geeksville.mesh.repository.location
+
+import android.annotation.SuppressLint
+import android.content.Context
+import android.location.Location
+import android.os.Looper
+import com.geeksville.mesh.android.GeeksvilleApplication
+import com.geeksville.mesh.android.Logging
+import com.geeksville.mesh.android.hasBackgroundPermission
+import com.google.android.gms.location.LocationCallback
+import com.google.android.gms.location.LocationRequest
+import com.google.android.gms.location.LocationResult
+import com.google.android.gms.location.LocationServices
+import kotlinx.coroutines.CoroutineScope
+import kotlinx.coroutines.channels.awaitClose
+import kotlinx.coroutines.flow.Flow
+import kotlinx.coroutines.flow.MutableStateFlow
+import kotlinx.coroutines.flow.SharingStarted
+import kotlinx.coroutines.flow.StateFlow
+import kotlinx.coroutines.flow.callbackFlow
+import kotlinx.coroutines.flow.shareIn
+
+/**
+ * Wraps LocationCallback() in callbackFlow
+ *
+ * Derived in part from https://github.com/android/location-samples/blob/main/LocationUpdatesBackgroundKotlin/app/src/main/java/com/google/android/gms/location/sample/locationupdatesbackgroundkotlin/data/MyLocationManager.kt
+ * and https://github.com/googlecodelabs/kotlin-coroutines/blob/master/ktx-library-codelab/step-06/myktxlibrary/src/main/java/com/example/android/myktxlibrary/LocationUtils.kt
+ */
+class SharedLocationManager constructor(
+    private val context: Context,
+    externalScope: CoroutineScope
+) : Logging {
+
+    private val _receivingLocationUpdates: MutableStateFlow<Boolean> = MutableStateFlow(false)
+    val receivingLocationUpdates: StateFlow<Boolean> get() = _receivingLocationUpdates
+
+    private val desiredInterval = 1 * 60 * 1000L
+
+    // Set up the Fused Location Provider and LocationRequest
+    private val fusedLocationClient = LocationServices.getFusedLocationProviderClient(context)
+    private val locationRequest = LocationRequest.create().apply {
+        interval = desiredInterval
+        fastestInterval = 30 * 1000L
+        maxWaitTime = 5 * 60 * 1000L
+        // smallestDisplacement = 30F // 30 meters
+        priority = LocationRequest.PRIORITY_BALANCED_POWER_ACCURACY
+    }
+
+    @SuppressLint("MissingPermission")
+    private val _locationUpdates = callbackFlow {
+        val callback = object : LocationCallback() {
+            override fun onLocationResult(result: LocationResult) {
+                // info("New location: ${result.lastLocation}")
+                trySend(result.lastLocation)
+            }
+        }
+        if (!context.hasBackgroundPermission()) close()
+
+        info("Starting location requests with interval=${desiredInterval}ms")
+        _receivingLocationUpdates.value = true
+        GeeksvilleApplication.analytics.track("location_start") // Figure out how many users needed to use the phone GPS
+
+        fusedLocationClient.requestLocationUpdates(
+            locationRequest,
+            callback,
+            Looper.getMainLooper()
+        ).addOnFailureListener { ex ->
+            errormsg("Failed to listen to GPS error: ${ex.message}")
+            close(ex) // in case of exception, close the Flow
+        }
+
+        awaitClose {
+            info("Stopping location requests")
+            _receivingLocationUpdates.value = false
+            GeeksvilleApplication.analytics.track("location_stop")
+            fusedLocationClient.removeLocationUpdates(callback) // clean up when Flow collection ends
+        }
+    }.shareIn(
+        externalScope,
+        replay = 0,
+        started = SharingStarted.WhileSubscribed()
+    )
+
+    fun locationFlow(): Flow<Location> {
+        return _locationUpdates
+    }
+}