Use manual foreground detection to trigger network reconnect

Author: schmidt-sebastian

firebase-firestore/src/main/java/com/google/firebase/firestore/remote/AndroidConnectivityMonitor.java

@@ -17,16 +17,20 @@
 import static com.google.firebase.firestore.util.Assert.hardAssert;
 
 import android.annotation.TargetApi;
+import android.app.Activity;
+import android.app.Application;
 import android.content.BroadcastReceiver;
 import android.content.Context;
 import android.content.Intent;
 import android.content.IntentFilter;
 import android.net.ConnectivityManager;
 import android.net.Network;
 import android.os.Build;
+import android.os.Bundle;
+import androidx.annotation.NonNull;
 import androidx.annotation.Nullable;
-import com.google.android.gms.common.api.internal.BackgroundDetector;
 import com.google.firebase.firestore.util.Consumer;
+import com.google.firebase.firestore.util.Logger;
 import java.util.ArrayList;
 import java.util.List;
 
@@ -36,8 +40,9 @@
  * <p>Implementation note: Most of the code here was shamelessly stolen from
  * https://github.com/grpc/grpc-java/blob/master/android/src/main/java/io/grpc/android/AndroidChannelBuilder.java
  */
-public final class AndroidConnectivityMonitor
-    implements ConnectivityMonitor, BackgroundDetector.BackgroundStateChangeListener {
+public final class AndroidConnectivityMonitor implements ConnectivityMonitor {
+
+  private static final String LOG_TAG = "AndroidConnectivityMonitor";
 
   private final Context context;
   @Nullable private final ConnectivityManager connectivityManager;
@@ -78,34 +83,56 @@ private void configureNetworkMonitoring() {
       final DefaultNetworkCallback defaultNetworkCallback = new DefaultNetworkCallback();
       connectivityManager.registerDefaultNetworkCallback(defaultNetworkCallback);
       unregisterRunnable =
-          new Runnable() {
-            @Override
-            public void run() {
-              connectivityManager.unregisterNetworkCallback(defaultNetworkCallback);
-            }
-          };
+          () -> connectivityManager.unregisterNetworkCallback(defaultNetworkCallback);
     } else {
       NetworkReceiver networkReceiver = new NetworkReceiver();
       @SuppressWarnings("deprecation")
       IntentFilter networkIntentFilter = new IntentFilter(ConnectivityManager.CONNECTIVITY_ACTION);
       context.registerReceiver(networkReceiver, networkIntentFilter);
-      unregisterRunnable =
-          new Runnable() {
-            @Override
-            public void run() {
-              context.unregisterReceiver(networkReceiver);
-            }
-          };
+      unregisterRunnable = () -> context.unregisterReceiver(networkReceiver);
     }
   }
 
   private void configureBackgroundStateListener() {
-    BackgroundDetector.getInstance().addListener(this);
+    // Manually register an ActivityLifecycleCallback. Android's BackgroundDetector only notifies
+    // when it is certain that the app transitioned from background to foreground. Instead, we
+    // want to be notified whenever there is a slight chance that this transition happened.
+    ((Application) context.getApplicationContext())
+        .registerActivityLifecycleCallbacks(
+            new Application.ActivityLifecycleCallbacks() {
+              @Override
+              public void onActivityCreated(@NonNull Activity activity, Bundle savedInstanceState) {
+                raiseForegroundNotification();
+              }
+
+              @Override
+              public void onActivityStarted(@NonNull Activity activity) {
+                raiseForegroundNotification();
+              }
+
+              @Override
+              public void onActivityResumed(@NonNull Activity activity) {
+                raiseForegroundNotification();
+              }
+
+              @Override
+              public void onActivityPaused(@NonNull Activity activity) {}
+
+              @Override
+              public void onActivityStopped(@NonNull Activity activity) {}
+
+              @Override
+              public void onActivitySaveInstanceState(
+                  @NonNull Activity activity, @NonNull Bundle outState) {}
+
+              @Override
+              public void onActivityDestroyed(@NonNull Activity activity) {}
+            });
   }
 
-  @Override
-  public void onBackgroundStateChanged(boolean background) {
-    if (!background && isConnected()) {
+  public void raiseForegroundNotification() {
+    Logger.debug(LOG_TAG, "App has entered the foreground.");
+    if (isConnected()) {
       raiseCallbacks(/* connected= */ true);
     }
   }

firebase-firestore/src/main/java/com/google/firebase/firestore/remote/OnlineStateTracker.java

@@ -88,6 +88,11 @@ interface OnlineStateCallback {
     shouldWarnClientIsOffline = true;
   }
 
+  /** Returns the current online state. */
+  OnlineState getState() {
+    return state;
+  }
+
   /**
    * Called by RemoteStore when a watch stream is started (including on each backoff attempt).
    *

firebase-firestore/src/main/java/com/google/firebase/firestore/remote/RemoteStore.java

@@ -216,7 +216,7 @@ public void onClose(Status status) {
 
                 // If the network has been explicitly disabled, make sure we don't accidentally
                 // re-enable it.
-                if (canUseNetwork()) {
+                if (!onlineStateTracker.getState().equals(OnlineState.ONLINE) && canUseNetwork()) {
                   // Tear down and re-create our network streams. This will ensure the backoffs are
                   // reset.
                   Logger.debug(LOG_TAG, "Restarting streams for network reachability change.");

subprojects.cfg

@@ -16,9 +16,6 @@ firebase-components:firebase-dynamic-module-support
 firebase-config
 firebase-config:ktx
 firebase-config:bandwagoner
-firebase-crashlytics
-firebase-crashlytics:ktx
-firebase-crashlytics-ndk
 firebase-database
 firebase-database:ktx
 firebase-database-collection