Flutter：抛出了 NoSuchMethodError。在 null 上调用了 getter 'type'

Question

您好，我目前正在使用 Flutter 开发移动应用。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，会抛出 NoSuchMethodError 说明在继续之前在红屏上的 null 上调用了 getter 一秒钟。但对象不为空。我不知道还能做什么。任何人都可以帮助我:( 2s 异常让我烦恼......

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，您在 null 上调用 type，这意味着在某些时候 profile 为 null，而您正试图在其上调用 type。您只需要在尝试使用之前检查profile 是否不为空