Flutter:类型 'Future<bool>' 不是类型转换中类型 'bool' 的子类型

Flutter: type 'Future<bool>' is not a subtype of type 'bool' in type cast

我正在尝试根据返回的值显示一个小部件。但是出现以下错误。

type 'Future<bool>' is not a subtype of type 'bool' in type cast

这是导致错误的源代码:

  Future<bool> fetchCourses() async {
    List courses = [];
    final loggedInUser = FirebaseAuth.instance.currentUser;
    if (loggedInUser != null) {
      final userCollection = await FirebaseFirestore.instance.collection('users').doc(loggedInUser.uid).get();
      courses = userCollection.get('coursesEnrolled');
    }
    if (courses.length == 0) {
      return false;
    } else {
      return true;
    }
  }
.
.
.
bool hasCourses = fetchCourses() as bool;
.
.
.
hasCourses ? ListAllUserEnrolledCourses() : Container(),
bool hasCourses = await fetchCourses();

你需要等待它完成,但不需要施放它。

fetchCourses()returns一个Future<bool>,用FutureBuilder解析Future.

FutureBuilder<bool>(
  future: fetchCourses(),
  builder: (_, snapshot) {
    if (snapshot.hasData) {
      return snapshot.data ? ListAllUserEnrolledCourses() : Container();
    }
    return Text('Loading...');
  },
),