颤振错误：无法在“SchedulerBinding”上调用方法“addPostFrameCallback”？因为它可能为空

Question

每当我尝试运行我的 Flutter 应用程序时，我都会收到此错误，它本来正在运行，但我不知道为什么现在却没有运行。我什至重置到之前的提交，但它仍然无法运行。

../../../development/flutter/.pub-cache/hosted/pub.dartlang.org/get-4.6.3/lib/get_navigation/src/extension_navigation.dart:357:33: Error: Method 'addPostFrameCallback' cannot be called on 'SchedulerBinding?' because it is potentially null.
 - 'SchedulerBinding' is from 'package:flutter/src/scheduler/binding.dart' ('../../../development/flutter/packages/flutter/lib/src/scheduler/binding.dart').
Try calling using ?. instead.
      SchedulerBinding.instance.addPostFrameCallback((_) {
                                ^^^^^^^^^^^^^^^^^^^^
../../../development/flutter/.pub-cache/hosted/pub.dartlang.org/get-4.6.3/lib/get_navigation/src/extension_navigation.dart:468:33: Error: Method 'addPostFrameCallback' cannot be called on 'SchedulerBinding?' because it is potentially null.
 - 'SchedulerBinding' is from 'package:flutter/src/scheduler/binding.dart' ('../../../development/flutter/packages/flutter/lib/src/scheduler/binding.dart').
Try calling using ?. instead.
      SchedulerBinding.instance.addPostFrameCallback((_) {
                                ^^^^^^^^^^^^^^^^^^^^
../../../development/flutter/.pub-cache/hosted/pub.dartlang.org/get-4.6.3/lib/get_navigation/src/snackbar/snackbar.dart:452:31: Error: Method 'addPostFrameCallback' cannot be called on 'SchedulerBinding?' because it is potentially null.
 - 'SchedulerBinding' is from 'package:flutter/src/scheduler/binding.dart' ('../../../development/flutter/packages/flutter/lib/src/scheduler/binding.dart').
Try calling using ?. instead.
    SchedulerBinding.instance.addPostFrameCallback(
                              ^^^^^^^^^^^^^^^^^^^^
../../../development/flutter/.pub-cache/hosted/pub.dartlang.org/get-4.6.3/lib/get_state_manager/src/rx_flutter/rx_notifier.dart:130:31: Error: Method 'addPostFrameCallback' cannot be called on 'SchedulerBinding?' because it is potentially null.
 - 'SchedulerBinding' is from 'package:flutter/src/scheduler/binding.dart' ('../../../development/flutter/packages/flutter/lib/src/scheduler/binding.dart').
Try calling using ?. instead.
    SchedulerBinding.instance.addPostFrameCallback((_) => onReady());
                              ^^^^^^^^^^^^^^^^^^^^
../../../development/flutter/.pub-cache/hosted/pub.dartlang.org/get-4.6.3/lib/get_state_manager/src/simple/get_controllers.dart:90:29: Error: Method 'addObserver' cannot be called on 'WidgetsBinding?' because it is potentially null.
 - 'WidgetsBinding' is from 'package:flutter/src/widgets/binding.dart' ('../../../development/flutter/packages/flutter/lib/src/widgets/binding.dart').
Try calling using ?. instead.
    WidgetsBinding.instance.addObserver(this);
                            ^^^^^^^^^^^
../../../development/flutter/.pub-cache/hosted/pub.dartlang.org/get-4.6.3/lib/get_state_manager/src/simple/get_controllers.dart:96:29: Error: Method 'removeObserver' cannot be called on 'WidgetsBinding?' because it is potentially null.
 - 'WidgetsBinding' is from 'package:flutter/src/widgets/binding.dart' ('../../../development/flutter/packages/flutter/lib/src/widgets/binding.dart').
Try calling using ?. instead.
    WidgetsBinding.instance.removeObserver(this);
                            ^^^^^^^^^^^^^^
../../../development/flutter/.pub-cache/hosted/pub.dartlang.org/get-4.6.3/lib/get_navigation/src/router_report.dart:53:31: Error: Method 'addPostFrameCallback' cannot be called on 'WidgetsBinding?' because it is potentially null.
 - 'WidgetsBinding' is from 'package:flutter/src/widgets/binding.dart' ('../../../development/flutter/packages/flutter/lib/src/widgets/binding.dart').
Try calling using ?. instead.
      WidgetsBinding.instance.addPostFrameCallback((_) {
                              ^^^^^^^^^^^^^^^^^^^^

失败：构建失败并出现异常。

* Where:
Script '/home/ibrahimdev/development/flutter/packages/flutter_tools/gradle/flutter.gradle' line: 1102

* What went wrong:
Execution failed for task ':app:compileFlutterBuildDebug'.
> Process 'command '/home/ibrahimdev/development/flutter/bin/flutter'' finished with non-zero exit value 1

* Try:
Run with --stacktrace option to get the stack trace. Run with --info or --debug option to get more log output. Run with --scan to get full insights.

* Get more help at https://help.gradle.org

18 秒内构建失败

Answer 1

Flutter 3.0.0 上次升级时，空安全属性发生了一些变化。有几种解决方法。

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1-) 如果您升级了最新的 Flutter 版本，并且错误出在 Flutter Core 代码中，您必须尝试；

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- dart fix --apply\n

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（参考：https ://docs.flutter.dev/development/tools/sdk/release-notes/release-notes-3.0.0 ）

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如果此解决方案不能修复任何错误，您可以降级 Flutter 版本；

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- flutter downgrade v2.10.5\n

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2-) 如果您没有升级或者错误出在第三方包中；

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1. 该包的开发者可能已将此包升级到最新版本的 Flutter。您可以使用以下方式升级软件包：

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   flutter pub upgrade --major-versions\n

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2. 如果开发人员尚未升级，您必须转到此包的 Github 存储库并查看问题选项卡。也许有人提出了一个问题，开发人员回答了正确的运行版本。例如，GetX与Flutter 2.10.5的最新兼容版本是4.6.1。因此，要应用此版本，您只需使用版本约束（删除 \xcb\x86）。

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更新

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get: \xcb\x864.6.1\n

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到

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get: 4.6.1\n

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在你的 pubspec 中。

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（参考：https: //github.com/jonataslaw/getx/issues/2356）

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