如何返回失败的任务导致继续执行任务? [英] How to return failed task result in continuation task?

问题描述

我正在Kotlin使用Google的Task API，并且面临下一种情况:

I am using Google's Task API in Kotlin and am faced with the next situation:

...
val deleteTask = getItem(id)?.continueWithTask { task ->
    if (task.isSuccessful)
        task.result?.toObject(ItemModel::class.java)?.let { deleteFiles(it.media) }
}

deleteTask?.continueWithTask { task ->
    if (task.isSuccessful) doSomething()
} ?: doSomething()
...

其中getItem(id)返回Firebase.firestore获取任务(Task<DocumentSnapshot>?)，而deleteFiles(it.media)检索Firebase.storage删除任务(Task<Void>?).如果出现以下情况，应调用doSomething():删除任务成功或根本不需要删除(deleteFiles(it.media)将返回null).

Where getItem(id) returns the Firebase.firestore get task (Task<DocumentSnapshot>?) and deleteFiles(it.media) retuens the Firebase.storage delete task (Task<Void>?). doSomething() should be called if either: the delete task succeed or no delete was needed at all (deleteFiles(it.media) would return null).

问题是当get任务失败时:在那种情况下，我希望deleteTask是一个非null的任务(因为null对于我来说是一个有效的情况，如所解释的)，并带有isSuccessful = false(所以不会被调用)，但是我找不到创建虚拟失败任务的方法.我曾考虑过要返回get任务(if (task.isSuccessful) ... else task)，但它给出了类型不匹配"信息.错误(由于Task<DocumentSnapshot>?和Task<Void>?是不同的类型，这很有意义...).

The problem is when the get task fails: In that case, I would like the deleteTask to be a non-null Task (as null is a valid case for me as explained) with isSuccessful = false (so doSomething() won't be called), but I couldn't find a way to create a dummy failed task. I thought about returning the get task (if (task.isSuccessful) ... else task), but it gives a "Type mismatch" error (which makes sense as Task<DocumentSnapshot>? and Task<Void>? are different types...).

那么，如何返回失败的任务导致继续执行任务?

So, How can I return a failed task result in a continuation task?

(有关为什么我需要这样做的更多信息:此处我用更多的细节解释了我的具体情况，但是据我从那里得到的答案了解，这些细节只会分散问题的注意力...)

(For more information on why I need this: here I explained my specific case with more details, but as I understood from the answer I got there, the details only distract from the question...)

推荐答案

好，我刚刚找到了想要的东西: Tasks API具有Tasks对象，该对象具有以下功能:forCanceled()& forResult().在我仅调查Task类并且不了解Tasks对象之前...有关更多信息，请参见

Ok, I just found what I've been looking for: Tasks API has a Tasks object which has functions: forCanceled() & forResult(). Before I only investigated the Task class and didn't know of the Tasks object... For more information, see here.

这篇关于如何返回失败的任务导致继续执行任务?的文章就介绍到这了，希望我们推荐的答案对大家有所帮助，也希望大家多多支持IT屋！