如何将Android Task转换为Kotlin Deferred?

问题描述

Firebase匿名登录返回任务(基本上是 Google承诺实现):

Firebase anonymous sign in returns a task (which is basically Google promise implementation):

val task:Task<AuthResult> = FirebaseAuth.getInstance().signInAnonymously()

如何创建signInAnonymous包装器，其中:

How it would be possible create a signInAnonymous wrapper where:

• 这是一个suspend函数，等待task完成

• suspend fun signInAnonymous(): Unit

它返回一个Deferred对象，异步传递结果

It returns a Deferred object, delivering the result asynchronously

• fun signInAnonymous() : Deferred

推荐答案

基于此GitHub库，这是一种将Task转换为通常"的方式基于回调的协程异步调用:

Based on this GitHub library, here's a way to transform a Task into a suspending function in the "usual" way to adapt callback based async calls to coroutines:

suspend fun <T> Task<T>.await(): T = suspendCoroutine { continuation ->
    addOnCompleteListener { task ->
        if (task.isSuccessful) {
            continuation.resume(task.result)
        } else {
            continuation.resumeWithException(task.exception ?: RuntimeException("Unknown task exception"))
        }
    }
}

您当然也可以将其包装在Deferred中，在这里CompletableDeferred会派上用场:

You can also wrap it in a Deferred of course, CompletableDeferred comes in handy here:

fun <T> Task<T>.asDeferred(): Deferred<T> {
    val deferred = CompletableDeferred<T>()

    deferred.invokeOnCompletion {
        if (deferred.isCancelled) {
            // optional, handle coroutine cancellation however you'd like here
        }
    }

    this.addOnSuccessListener { result -> deferred.complete(result) }
    this.addOnFailureListener { exception -> deferred.completeExceptionally(exception) }

    return deferred
}

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