asynchronous - Flutter : Failed assertion: line 146: '' : is not true 中的 Dart future 问题

Question

我正在为我的应用程序构建一个用户身份验证模块，但我遇到了一些异步代码的问题。

首先，这是抛出的错误:

E/flutter (17162): [ERROR:flutter/shell/common/shell.cc(188)] Dart Error: Unhandled exception: E/flutter (17162): 'dart:async/future_impl.dart': Failed assertion: line 146: 'optimized out': is not true. E/flutter (17162): #0 _AssertionError._doThrowNew (dart:core/runtime/liberrors_patch.dart:40:39) E/flutter (17162): #1 _AssertionError._throwNew (dart:core/runtime/liberrors_patch.dart:36:5) E/flutter (17162): #2 _FutureListener.handleError (dart:async/future_impl.dart:146:14) E/flutter (17162): #3 Future._propagateToListeners.handleError (dart:async/future_impl.dart:654:47) E/flutter (17162): #4 Future._propagateToListeners (dart:async/future_impl.dart:675:24) E/flutter (17162): #5 Future._completeError (dart:async/future_impl.dart:494:5) E/flutter (17162): #6 _SyncCompleter._completeError (dart:async/future_impl.dart:55:12) E/flutter (17162): #7 _Completer.completeError (dart:async/future_impl.dart:27:5) E/flutter (17162): #8 _AsyncAwaitCompleter.completeError (dart:async/runtime/libasync_patch.dart:40:18) E/flutter (17162): #9 FirebaseAuth.signInWithEmailAndPassword (package:firebase_auth/firebase_auth.dart) E/flutter (17162): E/flutter (17162): #10 Session.login. (package:mood_map/utilities/session.dart:31:24) E/flutter (17162): #11 _RootZone.runUnary (dart:async/zone.dart:1379:54) E/flutter (17162): #12 _FutureListener.handleValue (dart:async/future_impl.dart:129:18) E/flutter (17162): #13 Future._propagateToListeners.handleValueCallback (dart:async/future_impl.dart:642:45) E/flutter (17162): #14 Future._propagateToListeners (dart:async/future_impl.dart:671:32) E/flutter (17162): #15 Future._complete (dart:async/future_impl.dart:476:7) E/flutter (17162): #16 _SyncCompleter.complete (dart:async/future_impl.dart:51:12) E/flutter (17162): #17 _AsyncAwaitCompleter.complete (dart:async/runtime/libasync_patch.dart:28:18) E/flutter (17162): #18 _completeOnAsyncReturn (dart:async/runtime/libasync_patch.dart:295:13) E/flutter (17162): #19 Session._checkUserAlreadyExists (package:mood_map/utilities/session.dart) E/flutter (17162): E/flutter (17162): #20 Session.login (package:mood_map/utilities/session.dart:27:11)

这里是涉及的功能:

static final FirebaseAuth _authenticator = FirebaseAuth.instance;

static void login(BuildContext context, String email, String password) async {

email = email.trim();
password = password.trim();

//Check if the user already exists
await _checkUserAlreadyExists(email).then((exists) {

  if(exists) {

    _authenticator.signInWithEmailAndPassword(email: email, password: password)
        .then((FirebaseUser user) { _loginSuccess(); })
        .catchError((Error e) { _loginFailure(context); });

  } else {

    Utilities.showMessageDialog(context, "That user doesn't exist. Please create an account below.");

  }

});

} 

----------------------------------------------------------------------

static Future createUserAccount(BuildContext context, email, String password) async {

//Check if the user already exists
await _checkUserAlreadyExists(email).then((exists) {

  if(exists) {

    Utilities.showMessageDialog(context, "That user already exists. Please login or select another account.");
    AppNavigator.navigateToLoginScreen();

  } else {

    _authenticator.createUserWithEmailAndPassword(email: email, password: password)
        .then((FirebaseUser user) { _createUserSuccess(); })
        .catchError((Error e) { _createUserFailure(context); });

  }

});

}

简而言之，对 _authenticator.signonWithEmailAndPassword() 的调用失败。我知道 _authenticator 实例正在使用其他函数，所以我知道这不是 Firebase 本身的问题。

我担心我从另一个异步函数 _checkIfUserAlreadyExists() 中调用另一个异步函数 _authenticator.signonWithEmailAndPassword() 做错了事。从我读过的内容来看，这似乎可以在 .then() block 中执行，但错误消息似乎非常坚持认为这与函数调用的异步性质的设置有关。

想法？

Answer 1

如果您使用 .then() 子句，请不要使用 await。

.then() 和 await 是处理 Future 的两种不同方式，但不应用于相同的 future 实例。