Fix NetworkOnMainThreadException for API levels below 26

firebase-config/CHANGELOG.md

@@ -1,8 +1,8 @@
 # Unreleased
-
+* [fixed] Fixed `NetworkOnMainThreadException` on Android versions below 8 by disconnecting HttpURLConnection only on API levels 26 and higher.
 
 # 22.1.1
-[fixed] Fixed an issue where the connection to the real-time Remote Config backend could remain
+* [fixed] Fixed an issue where the connection to the real-time Remote Config backend could remain
 open in the background.
 
 

firebase-config/src/main/java/com/google/firebase/remoteconfig/internal/ConfigRealtimeHttpClient.java

@@ -22,6 +22,7 @@
 import android.annotation.SuppressLint;
 import android.content.Context;
 import android.content.pm.PackageManager;
+import android.os.Build;
 import android.util.Log;
 import androidx.annotation.GuardedBy;
 import androidx.annotation.NonNull;
@@ -409,8 +410,13 @@ public void setIsInBackground(boolean isInBackground) {
       }
       // Close the connection if the app is in the background and there is an active
       // HttpUrlConnection.
-      if (isInBackground && httpURLConnection != null) {
-        httpURLConnection.disconnect();
+      // This is now only done on Android versions >= O (API 26) because
+      // on older versions, background detection callbacks run on the main thread, which
+      // could lead to a NetworkOnMainThreadException when disconnecting the connection.
+      if (Build.VERSION.SDK_INT >= Build.VERSION_CODES.O) {
+        if (isInBackground && httpURLConnection != null) {
+          httpURLConnection.disconnect();
+        }
       }
     }
   }