我面临一个错误FAILURE:构建失败并出现异常

Question

我有这个错误:

-/C:/src/flutter/flutter/packages/flutter/lib/src/services/asset_bundle.dart:240:12: Error: A value of type 'ByteData?' can't be returned from an async function with return type 'Future<ByteData>' because 'ByteData?' is nullable and 'Future<ByteData>' isn't.
- 'ByteData' is from 'dart:typed_data'.
- 'Future' is from 'dart:async'.
return asset;
^

FAILURE: Build failed with an exception.
* Where:
Script 'C:srcflutterflutterpackagesflutter_toolsgradleflutter.gradle' line: 1156
* What went wrong:
Execution failed for task ':app:compileFlutterBuildDebug'.
> Process 'command 'C:srcflutterflutterbinflutter.bat'' finished with non-zero exit value 1
* Try:
> Run with --stack trace 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
BUILD FAILED in 48s
Exception: Gradle task assembly debug failed with exit code 1

Answer 1

这是一个可空性问题。
在您的情况下，一个函数试图返回Future<ByteData?>，而它应该返回Future<ByteData>。这个问号很重要。它表明ByteData?可能为空，而ByteData可能不为空。如果上下文已经确定返回的值不为空，则只需将返回语句修改为

...
return result!;

感叹号确保结果值不是零,把一个错误在运行时如果是null。
当然，如果这个函数的结果可能是null，那么将它的签名重写为Future<ByteData?>

会更合适。