withContext总是返回false

Question

ViewModel类：

            // Update the userInformation and returns Boolean if the operation succeed
            val res = viewModelScope.async {
                accountRepository.update(
                    userId,
                    firstName,
                    lastName,
                    birthDate,
                    photoUrl
                )
            }

            // This should execute
            // But the result is always false and go to the else part.
            if (res.await()) {
                ...
            } else {
                // But it always goes here
                ...
            }

我的存储库中的update函数正在执行中，我可以看到Firestore中的更改，没有问题。但是结果总是错误的，在我看来，ViewModel给出了一个错误的状态，我不喜欢它。我认为问题在withContext部分。我不完全理解它，但也许你可以给我关于如何解决这个问题的见解。我

这是我的AccountRepository类的代码：

// Account Repository
// Update the user information
suspend fun update(
    userId: String,
    firstName: String,
    lastName: String,
    birthDate: String,
    avatarUrl: String
): Boolean {
    return withContext(dispatcher) {
        // This will be true for now
        var isSuccess = true

        // Parsing the date string "01/01/2000" to a date object
        val date = SimpleDateFormat("MM/dd/yyyy", Locale.ENGLISH).parse(birthDate)

        // Creating an instance of calendar object
        val calendarDate = Calendar.getInstance()
        // Set the time with the date variable
        calendarDate.time = date!!

        // Check if the user is in the right age to use the application
        // User should be 12 years old and above to access this app
        if (Calendar.getInstance().get(Calendar.YEAR)
            .minus(calendarDate.get(Calendar.YEAR)) >= 12
        ) {

            // Create a map to update fields in the firebase
            val updateUserMap = mapOf<String, Any>(
                "avatarUrl" to avatarUrl,
                "firstName" to firstName,
                "lastName" to lastName,
                "birthDate" to birthDate,
                "dateModified" to Utils.getTimeInMillisUTC()
            )

            // Execute the query in fireStore
            // I'm using ktx gradle library
            // This line executes. It reflects the changes in the fireStore
            val result = userCollectionRef
                .document(userId)
                .set(updateUserMap, SetOptions.merge())
                .await()

            // The variable will be changed to false when the result is null
            // Meaning that the query is not successful
            if (result == null) {
                isSuccess = false
            }
        }
        // Return the variable after all operations
        isSuccess
    }
}

Answer 1

当结果为null时，变量将更改为false，这意味着查询不成功。

我想这就是你错的地方。从文档来看，document.set()只返回一个在查询结束时将完成的任务，但它并没有说null将被用作失败的标志。

另外，您使用的等待函数将Task故障表示为抛出的异常(在协同中非常常见，我们通常将挂起函数中的故障与其他函数中的故障一样处理)。

如果您想要处理错误，您可能应该使用try-catch而不是if (result == null)。