Polling only happens when app is in foreground

relaycorp · Sep 29, 2022 · 93d0403 · 93d0403
1 parent 0ce7b0b
commit 93d0403
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Showing 3 changed files with 60 additions and 12 deletions.
diff --git a/app/src/main/java/tech/relaycorp/courier/App.kt b/app/src/main/java/tech/relaycorp/courier/App.kt
@@ -3,6 +3,7 @@ package tech.relaycorp.courier
 import android.app.Application
 import android.os.Build
 import android.os.StrictMode
+import tech.relaycorp.courier.background.ForegroundAppMonitor
 import tech.relaycorp.courier.background.WifiHotspotStateWatcher
 import tech.relaycorp.courier.common.Logging
 import tech.relaycorp.courier.common.di.AppComponent
@@ -16,6 +17,9 @@ open class App : Application() {
     @Inject
     lateinit var wifiHotspotStateWatcher: WifiHotspotStateWatcher
 
+    @Inject
+    lateinit var foregroundAppMonitor: ForegroundAppMonitor
+
     open val component: AppComponent by lazy {
         DaggerAppComponent.builder()
             .appModule(AppModule(this))
@@ -36,6 +40,7 @@ open class App : Application() {
         component.inject(this)
         setupLogger()
         setupStrictMode()
+        registerActivityLifecycleCallbacks(foregroundAppMonitor)
         wifiHotspotStateWatcher.start()
     }
 

diff --git a/app/src/main/java/tech/relaycorp/courier/background/ForegroundAppMonitor.kt b/app/src/main/java/tech/relaycorp/courier/background/ForegroundAppMonitor.kt
@@ -0,0 +1,35 @@
+package tech.relaycorp.courier.background
+
+import android.app.Activity
+import android.app.Application
+import android.os.Bundle
+import kotlinx.coroutines.flow.MutableStateFlow
+import kotlinx.coroutines.flow.map
+import javax.inject.Inject
+import javax.inject.Singleton
+
+@Singleton
+class ForegroundAppMonitor
+@Inject constructor() : Application.ActivityLifecycleCallbacks {
+    private val activityCountFlow = MutableStateFlow(0)
+
+    fun observe() = activityCountFlow.map { if (it == 0) State.Background else State.Foreground }
+
+    override fun onActivityStarted(activity: Activity) {
+        activityCountFlow.value++
+    }
+
+    override fun onActivityStopped(activity: Activity) {
+        activityCountFlow.value--
+    }
+
+    override fun onActivityCreated(activity: Activity, savedInstanceState: Bundle?) = Unit
+    override fun onActivityResumed(activity: Activity) = Unit
+    override fun onActivityPaused(activity: Activity) = Unit
+    override fun onActivitySaveInstanceState(activity: Activity, outState: Bundle) = Unit
+    override fun onActivityDestroyed(activity: Activity) = Unit
+
+    enum class State {
+        Foreground, Background
+    }
+}
diff --git a/app/src/main/java/tech/relaycorp/courier/background/WifiHotspotStateWatcher.kt b/app/src/main/java/tech/relaycorp/courier/background/WifiHotspotStateWatcher.kt
@@ -8,15 +8,16 @@ import android.net.wifi.WifiManager
 import kotlinx.coroutines.CoroutineScope
 import kotlinx.coroutines.Dispatchers
 import kotlinx.coroutines.Job
-import kotlinx.coroutines.channels.trySendBlocking
-import kotlinx.coroutines.flow.asFlow
+import kotlinx.coroutines.flow.MutableStateFlow
+import kotlinx.coroutines.flow.asStateFlow
 import kotlinx.coroutines.flow.distinctUntilChanged
+import kotlinx.coroutines.flow.emptyFlow
+import kotlinx.coroutines.flow.flatMapLatest
 import kotlinx.coroutines.flow.launchIn
 import kotlinx.coroutines.flow.map
 import kotlinx.coroutines.flow.onEach
 import tech.relaycorp.cogrpc.server.GatewayIPAddressException
 import tech.relaycorp.cogrpc.server.Networking
-import tech.relaycorp.courier.common.BehaviorChannel
 import tech.relaycorp.courier.common.Logging.logger
 import tech.relaycorp.courier.common.tickerFlow
 import javax.inject.Inject
@@ -26,11 +27,12 @@ import kotlin.time.Duration.Companion.seconds
 @Singleton
 class WifiHotspotStateWatcher
 @Inject constructor(
-    private val context: Context
+    private val context: Context,
+    private val foregroundAppMonitor: ForegroundAppMonitor
 ) {
 
-    private val state = BehaviorChannel(WifiHotspotState.Disabled)
-    fun state() = state.asFlow().distinctUntilChanged()
+    private val state = MutableStateFlow(WifiHotspotState.Disabled)
+    fun state() = state.asStateFlow()
 
     private var pollingGatewayAddressesJob: Job? = null
 
@@ -54,8 +56,14 @@ class WifiHotspotStateWatcher
     }
 
     private fun startPollingGatewayAddresses() {
-        pollingGatewayAddressesJob = tickerFlow(POLLING_GATEWAY_ADDRESS_INTERVAL)
-            .map {
+        pollingGatewayAddressesJob = foregroundAppMonitor.observe()
+            .flatMapLatest {
+                if (it == ForegroundAppMonitor.State.Foreground) {
+                    tickerFlow(POLLING_GATEWAY_ADDRESS_INTERVAL)
+                } else {
+                    emptyFlow()
+                }
+            }.map {
                 try {
                     Networking.getGatewayIpAddress()
                     WifiHotspotState.Enabled
@@ -66,13 +74,14 @@ class WifiHotspotStateWatcher
             .distinctUntilChanged()
             .onEach {
                 logger.info("Hotspot State $it")
-                state.send(it)
+                state.value = it
             }
             .launchIn(CoroutineScope(Dispatchers.IO))
     }
 
     private fun stopPollingGatewayAddresses() {
         pollingGatewayAddressesJob?.cancel()
+        pollingGatewayAddressesJob = null
     }
 
     private val wifiApStateChangeReceiver by lazy {
@@ -81,14 +90,13 @@ class WifiHotspotStateWatcher
                 if (intent.action != WIFI_AP_STATE_CHANGED_ACTION) return
 
                 val stateFlag = intent.getIntExtra(WifiManager.EXTRA_WIFI_STATE, 0)
-                logger.info("Wifi State $stateFlag")
-                state.trySendBlocking(
+                logger.info("Hotspot State $stateFlag")
+                state.value =
                     if (stateFlag == WIFI_AP_STATE_ENABLED) {
                         WifiHotspotState.Enabled
                     } else {
                         WifiHotspotState.Disabled
                     }
-                )
             }
         }
     }