Flutter集成Firebase后assembleRelease构建APK失败求助

我正在开发首个Flutter+Firebase应用，未集成Firebase前曾成功构建过一次。目前开发进度已完成90%，但无法构建APK，也无法修复构建时出现的错误，特此求助。

构建命令及错误输出 #

C:\Users\Asus\flutter\bin\flutter.bat --no-color build apk

Building without sound null safety
For more information see https://dart.dev/null-safety/unsound-null-safety

Running Gradle task 'assembleRelease'...                        
../../flutter/.pub-cache/hosted/pub.dartlang.org/charts_flutter-0.12.0/lib/src/chart_container.dart:205:27: Warning: Operand of null-aware operation '!' has type 'SchedulerBinding' which excludes null.
 - 'SchedulerBinding' is from 'package:flutter/src/scheduler/binding.dart' ('../../flutter/packages/flutter/lib/src/scheduler/binding.dart').
    if (!SchedulerBinding.instance!.hasScheduledFrame) {
                          ^
../../flutter/.pub-cache/hosted/pub.dartlang.org/charts_flutter-0.12.0/lib/src/chart_container.dart:206:24: Warning: Operand of null-aware operation '!' has type 'SchedulerBinding' which excludes null.
 - 'SchedulerBinding' is from 'package:flutter/src/scheduler/binding.dart' ('../../flutter/packages/flutter/lib/src/scheduler/binding.dart').
      SchedulerBinding.instance!.scheduleFrame();
                       ^
../../flutter/.pub-cache/hosted/pub.dartlang.org/charts_flutter-0.12.0/lib/src/chart_container.dart:209:22: Warning: Operand of null-aware operation '!' has type 'SchedulerBinding' which excludes null.
 - 'SchedulerBinding' is from 'package:flutter/src/scheduler/binding.dart' ('../../flutter/packages/flutter/lib/src/scheduler/binding.dart').
    SchedulerBinding.instance!.addPostFrameCallback(startAnimationController);
                     ^
../../flutter/.pub-cache/hosted/pub.dartlang.org/charts_flutter-0.12.0/lib/src/chart_container.dart:232:22: Warning: Operand of null-aware operation '!' has type 'SchedulerBinding' which excludes null.
 - 'SchedulerBinding' is from 'package:flutter/src/scheduler/binding.dart' ('../../flutter/packages/flutter/lib/src/scheduler/binding.dart').
    SchedulerBinding.instance!.addPostFrameCallback(doRebuild);
                 ^

问题分析与解决办法 #

这些警告来自charts_flutter:0.12.0包，原因是该版本代码在新版本Flutter中使用了不必要的空断言符!——新版本Flutter里SchedulerBinding.instance已被标记为非空类型，无需再加!。

解决步骤：

• 优先升级charts_flutter到最新稳定版，新版本大概率已修复空安全适配问题。修改pubspec.yaml中的依赖版本后执行flutter pub get。
• 若升级包后问题仍存在或无法升级（如依赖冲突），可使用dependency_overrides强制拉取修复后的源码：
  1. 在pubspec.yaml末尾添加：

     dependency_overrides:
       charts_flutter:
         git:
           url: https://github.com/google/charts.git
           path: charts_flutter
           ref: main
     

  2. 执行flutter pub get重新拉取依赖。
• 若构建仍失败，尝试先执行flutter clean清理缓存，再重新运行flutter build apk。

内容的提问来源于stack exchange，提问作者Djèlì Bi Berci