It would help if you provide a small complete application that demonstrates the problem you've run into. Thanks!

@HansMuller Here is a small test project: https://github.com/leisim/dialogapp

@HansMuller is this a flutter issue or am I doing anything wrong?

@leisim https://github.com/NMateu/flutter_transparent_app

Some explanation:

1. To make an android app transparent you must edit a app style https://github.com/NMateu/flutter_transparent_app/blob/master/android/app/src/main/res/values/styles.xml
2. Apply this theme in manifest https://github.com/NMateu/flutter_transparent_app/blob/master/android/app/src/main/AndroidManifest.xml#L16
3. Enable Flutter transparent view in MainActivity https://github.com/NMateu/flutter_transparent_app/blob/master/android/app/src/main/java/com/example/flutter_transparent_app/MainActivity.java#L14

After this your Android activity is transparent. Until you use MaterialApp or WidgetApp in the flutter code, it will remain so.

To show dialog in flutter I must use a showGeneralDialog function because showDialog uses a MediaQuery which is dependent of MaterialApp or WidgetApp https://github.com/NMateu/flutter_transparent_app/blob/master/lib/main.dart#L78

The last condition to display the dialog is to wrap AlertDialog in MaterialApp widget https://github.com/NMateu/flutter_transparent_app/blob/master/lib/main.dart#L84

@HansMuller is there any reason why MaterialApp or WidgetApp cannot be transparent? It would be much easier...

@NMateu Thank you that really helps me. But it would be nice if it was less complicated to use material widgets...

Thanks @NMateu for your detailed explanation. Your sample project was very helpful in allowing me to setup a transparent FlutterView correctly. Many thanks!

@leisim I think it can be done with just

    return MaterialApp(
      builder: (context, child) {
        return Scaffold(
          backgroundColor: Colors.transparent, // <------ this
...

@phanirithvij Unfortunately the background is just black if I try that...

@leisim I mean after following this #28844 (comment).

This is a demo app similar to @NMateu's flutter_transparent_app.

https://github.com/phanirithvij/invisible_flutter