Flutter：抛出 NoSuchMethodError。 getter 'type' 被调用为 null

Question

您好，我目前正在使用 Flutter 开发移动应用程序。我的程序有两种类型的用户，所以我需要根据数据类型来调整用户。因此，在检查用户数据时，抛出了一个 NoSuchMethodError，指出 getter 在红屏上被调用了一秒钟，然后再继续。但该对象不为空。我不知道还能做什么。任何人都可以帮助我:( 2s 异常让我很烦...

final profile = Provider.of<Profile>(context);

if (profile.type == null) {
  return Center(
    child: CircularProgressIndicator(
      backgroundColor: Colors.white,
    ),
  );
} else {
  return MaterialApp(
    home: profile.type ? SessionWrapperTutor() : SessionWrapperTutee(), //here the problem occur
  );

这是错误

════════ Exception caught by widgets library ═══════════════════════════════════

The following NoSuchMethodError was thrown building HomeWrapper(dirty, dependencies: [InheritedProvider<Profile>], state: _HomeWrapperState#91be8):

The getter 'type' was called on null.
Receiver: null
Tried calling: type

The relevant error-causing widget was HomeWrapper
When the exception was thrown, this was the stack

#0      Object.noSuchMethod
#1      _HomeWrapperState.build
#2      StatefulElement.build
#3      ComponentElement.performRebuild
#4      StatefulElement.performRebuild

Answer 1

正如异常告诉您的那样，您正在对 null 调用 type，这意味着在某个时刻 profile 为 null，并且您正试图对其调用 type。您只需要在尝试使用它之前检查 profile 是否不为 null

Flutter：抛出 NoSuchMethodError。 getter 'type' 被调用为 null

Flutter: NoSuchMethodError was thrown. The getter 'type' was called on null

dart

firebase

flutter

flutter-dependencies

flutter-provider