update

[dackArrogant]

../../../../../Documents/flutter/.pub-cache/hosted/pub.flutter-io.cn/flare_flutter-3.0.2/lib/flare_render_box.dart:167:26: Warning: Operand of null-aware operation '?.' has type 'SchedulerBinding' which excludes null.
- 'SchedulerBinding' is from 'package:flutter/src/scheduler/binding.dart' ('../../../../../Documents/flutter/packages/flutter/lib/src/scheduler/binding.dart').
SchedulerBinding.instance?.cancelFrameCallbackWithId(_frameCallbackID);

[tsinis]

../../../../../Documents/flutter/.pub-cache/hosted/pub.flutter-io.cn/flare_flutter-3.0.2/lib/flare_render_box.dart:167:26: Warning: Operand of null-aware operation '?.' has type 'SchedulerBinding' which excludes null. - 'SchedulerBinding' is from 'package:flutter/src/scheduler/binding.dart' ('../../../../../Documents/flutter/packages/flutter/lib/src/scheduler/binding.dart'). SchedulerBinding.instance?.cancelFrameCallbackWithId(_frameCallbackID);

It seems like this package is not maintained anymore, you will probably have to move to Rive 2 soon. Otherwise, you can use it like that. Basically provide dependency from the update PR.