title: Flutter Firebase callbacks are not fired on iOS 13, but work fine on Android
body: <p>I'm currently developing a flutter app, when I've experienced the following:</p>
  
  <p>On Android, everything works as expected. If the app is in foreground, <code>onMessage</code> is called, <code>onLaunch</code> and so on if the app was in background.</p>
  
  <p>On iOS (13), none of the callbacks are called. The notification arrives, is showing the correct icon, text and title, when I click on the notification the app opens, but none of the callbacks are fired. If the app is already in foreground, no Notification is shown (as expected), but <code>onMessage</code> isn't called either.</p>
  
  <p>Here is the payload I'm sending:</p>
  
  <pre><code>{
    "data": {
      "click_action": "FLUTTER_NOTIFICATION_CLICK",
      "key1": "value1"
    },
    "to": "RECEIVER",
    "notification": {
      "sound": "default",
      "title": "Title",
      "body": "Message"
    }
  }
  </code></pre>
  
  <p>Flutter code:</p>
  
  <pre class="lang-dart prettyprint-override"><code>firebaseMessaging.configure(
    onMessage: (Map&lt;String, dynamic&gt; message) {
      log.info('Firebase::onMessage: $message');
  
      _handleMessage(message);
    },
    onResume: (Map&lt;String, dynamic&gt; message) {
      log.info('Firebase::onResume: $message');
  
      _handleMessage(message);
    },
    onLaunch: (Map&lt;String, dynamic&gt; message) {
      log.info('Firebase::onLaunch: $message');
  
      _handleMessage(message);
    },
  );
  </code></pre>
  
  <p>AppDelegate.swift:</p>
  
  <p>I've tried to run the app with and without the following lines</p>
  
  <pre class="lang-swift prettyprint-override"><code>if #available(iOS 10.0, *) {
      UNUserNotificationCenter.current().delegate = self as? UNUserNotificationCenterDelegate
  }
  </code></pre>
  
  <p>I have enabled push notifications, background fetch and remote notifications in the capabilities tab in XCode.</p>
  
  <p>I am running Flutter 1.12.13 (beta channel), however I also tried to run the app with flutter stable, which resulted in the same behavior.</p>
  
  <pre><code>[✓] Flutter (Channel beta, v1.12.13+hotfix.3, on Mac OS X 10.15.1 19B88, locale en-DE)
      • Flutter version 1.12.13+hotfix.3 at /usr/local/bin/flutter
      • Framework revision 57f2df76d7 (3 days ago), 2019-12-05 21:23:21 -0800
      • Engine revision ac9391978e
      • Dart version 2.7.0
  
  [✓] Android toolchain - develop for Android devices (Android SDK version 29.0.2)
      • Android SDK at /Users/martin/Library/Android/sdk
      • Android NDK location not configured (optional; useful for native profiling support)
      • Platform android-29, build-tools 29.0.2
      • Java binary at: /Users/martin/Library/Application Support/JetBrains/Toolbox/apps/AndroidStudio/ch-0/191.6010548/Android Studio.app/Contents/jre/jdk/Contents/Home/bin/java
      • Java version OpenJDK Runtime Environment (build 1.8.0_202-release-1483-b49-5587405)
      • All Android licenses accepted.
  
  [✓] Xcode - develop for iOS and macOS (Xcode 11.2.1)
      • Xcode at /Applications/Xcode.app/Contents/Developer
      • Xcode 11.2.1, Build version 11B500
      • CocoaPods version 1.8.4
  
  [✓] Android Studio (version 3.5)
      • Android Studio at /Users/martin/Library/Application Support/JetBrains/Toolbox/apps/AndroidStudio/ch-0/191.6010548/Android Studio.app/Contents
      • Flutter plugin version 40.0.2
      • Dart plugin version 191.8423
      • Java version OpenJDK Runtime Environment (build 1.8.0_202-release-1483-b49-5587405)
  
  [!] IntelliJ IDEA Ultimate Edition (version 2019.3)
      • IntelliJ at /Users/martin/Applications/JetBrains Toolbox/IntelliJ IDEA Ultimate.app
      ✗ Flutter plugin not installed; this adds Flutter specific functionality.
      ✗ Dart plugin not installed; this adds Dart specific functionality.
      • For information about installing plugins, see
        https://flutter.dev/intellij-setup/#installing-the-plugins
  
  [!] Connected device
      ! No devices available
  
  ! Doctor found issues in 2 categories.
  </code></pre>
  
  <p>Thanks in advance!</p>