试试Fluter 3的游戏功能，嗨挺好玩的
Flutter 3 需要常用映射的地址为 中国镜像站点
export PUB_HOSTED_URL=pub.flutter-io.cn
export FLUTTER_STORAGE_BASE_URL=storage.flutter-io.cn
错误提示 warning 页面是空白的
`flutter run -d chrome Launching lib/main.dart on Chrome in debug mode... ../../tools/flutter/.pub-cache/hosted/mirrors.tuna.tsinghua.edu.cn%2547dart-pub%2547/flame_audio-1.0.2/lib/b gm.dart:38:20: Warning: Operand of null-aware operation '?.' has type 'WidgetsBinding' which excludes null.
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'WidgetsBinding' is from 'package:flutter/src/widgets/binding.dart' ('../../tools/flutter/packages/flutter/lib/src/widgets/binding.dart'). WidgetsBinding.instance?.addObserver(this); ^ ../../tools/flutter/.pub-cache/hosted/mirrors.tuna.tsinghua.edu.cn%2547dart-pub%2547/flame_audio-1.0.2/lib/b gm.dart:46:20: Warning: Operand of null-aware operation '?.' has type 'WidgetsBinding' which excludes null.
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'WidgetsBinding' is from 'package:flutter/src/widgets/binding.dart' ('../../tools/flutter/packages/flutter/lib/src/widgets/binding.dart'). WidgetsBinding.instance?.removeObserver(this); ^ ../../tools/flutter/.pub-cache/hosted/mirrors.tuna.tsinghua.edu.cn%2547dart-pub%2547/flame-1.1.1/lib/src/gam e/game_render_box.dart:13:20: Warning: Operand of null-aware operation '!' has type 'WidgetsBinding' which excludes null.
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'WidgetsBinding' is from 'package:flutter/src/widgets/binding.dart' ('../../tools/flutter/packages/flutter/lib/src/widgets/binding.dart'). WidgetsBinding.instance!.addTimingsCallback(game.onTimingsCallback); ^ ../../tools/flutter/.pub-cache/hosted/mirrors.tuna.tsinghua.edu.cn%2547dart-pub%2547/flame-1.1.1/lib/src/gam e/game_render_box.dart:68:20: Warning: Operand of null-aware operation '!' has type 'WidgetsBinding' which excludes null.
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'WidgetsBinding' is from 'package:flutter/src/widgets/binding.dart' ('../../tools/flutter/packages/flutter/lib/src/widgets/binding.dart'). WidgetsBinding.instance!.addObserver(this); ^ ../../tools/flutter/.pub-cache/hosted/mirrors.tuna.tsinghua.edu.cn%2547dart-pub%2547/flame-1.1.1/lib/src/gam e/game_render_box.dart:72:20: Warning: Operand of null-aware operation '!' has type 'WidgetsBinding' which excludes null.
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'WidgetsBinding' is from 'package:flutter/src/widgets/binding.dart' ('../../tools/flutter/packages/flutter/lib/src/widgets/binding.dart'). WidgetsBinding.instance!.removeObserver(this);
`
