title: How set custom sound notification on background in flutter?
body: <p>I wrote a flutter application and I can't configure the firebase cloud messaging with custom sound. I get notifications, but they come with the default sound while the app is in background. In the foreground, I use the local notification library and it works well, but I need to work in background too.</p>
  <p>This is what I send for the cloud messaging:</p>
  <pre><code>{
     &quot;to&quot;:&quot;&lt;firebase_token&gt;&quot;,
     &quot;notification&quot;:{
        &quot;sound&quot;:&quot;arrive&quot;,
        &quot;title&quot;:&quot;My Title&quot;,
        &quot;body&quot;:&quot;My body&quot;
     },
     &quot;data&quot;:{
        &quot;click_action&quot;:&quot;FLUTTER_NOTIFICATION_CLICK&quot;,
        &quot;status&quot;:&quot;done&quot;,
        &quot;screen&quot;:&quot;screenA&quot;,
        &quot;message&quot;:&quot;ACTION&quot;
     },
     &quot;apns&quot;:{
        &quot;headers&quot;:{
           &quot;apns-priority&quot;:&quot;5&quot;,
           &quot;apns-push-type&quot;:&quot;background&quot;
        },
        &quot;payload&quot;:{
           &quot;aps&quot;:{
              &quot;content-available&quot;:1
           }
        }
     }
  }
  </code></pre>
  <p>This is my working local notification config:</p>
  <pre><code>void showNotification({
      String title,
      String body,
    }) {
      var androidPlatformChannelSpecifics = AndroidNotificationDetails(
        'your channel id',
        'your channel name',
        'your channel description',
        importance: Importance.Max,
        priority: Priority.Max,
        ticker: 'ticker',
        playSound: true,
        sound: RawResourceAndroidNotificationSound('arrive')
      );
  
      var iOSPlatformChannelSpecifics = IOSNotificationDetails();
  
      var platformChannelSpecifics = NotificationDetails(
        androidPlatformChannelSpecifics,
        iOSPlatformChannelSpecifics,
      );
      notifications.show(0, title, body, platformChannelSpecifics,
          payload: 'Custom_Sound',);
    }
  </code></pre>
  <p>So the local notifications library see my custom sound, but cloud messaging will play the default sound. What could be the problem?</p>
  <p>My sound is located at: android\app\src\main\res\raw\arrive.mp3</p>
  <p>My imports are:</p>
  <pre><code>    flutter_local_notifications: ^1.4.3 
      firebase_messaging: ^6.0.16
  </code></pre>
  <p>Flutter doctor:</p>
  <pre><code>[√] Flutter (Channel stable, v1.12.13+hotfix.9, on Microsoft Windows [Version 10.0.18362.836], locale hu-HU)
      • Flutter version 1.12.13+hotfix.9 at C:\flutter src\flutter
      • Framework revision f139b11009 (8 weeks ago), 2020-03-30 13:57:30 -0700
      • Engine revision af51afceb8
      • Dart version 2.7.2
  
   
  [√] Android toolchain - develop for Android devices (Android SDK version 28.0.3)
      • Android SDK at C:\Users\koros\AppData\Local\Android\sdk
      • Android NDK location not configured (optional; useful for native profiling support)
      • Platform android-29, build-tools 28.0.3
      • Java binary at: C:\Program Files\Android\Android Studio\jre\bin\java
      • Java version OpenJDK Runtime Environment (build 1.8.0_152-release-1343-b01)
      • All Android licenses accepted.
  
  [√] Android Studio (version 3.4)
      • Android Studio at C:\Program Files\Android\Android Studio
      • Flutter plugin version 35.3.1
      • Dart plugin version 183.6270
      • Java version OpenJDK Runtime Environment (build 1.8.0_152-release-1343-b01)
  
  [√] VS Code (version 1.45.1)
      • VS Code at C:\Users\koros\AppData\Local\Programs\Microsoft VS Code
      • Flutter extension version 3.10.2
  
  [√] Connected device (1 available)
      • SM A520F • 52003aa8f4ea64d5 • android-arm64 • Android 8.0.0 (API 26) (emulator)
  
  • No issues found!
  </code></pre>