调用Continuation.resumeX()失败一定是个问题吗？

Question

我使用suspendCoroutine是为了避免在Dialogs中使用回调。然而，在Android Dialogs中，当对话框被关闭时(通过在对话框区域之外单击)，没有明显的地方可以调用Continuation.resume()。如果您尝试在Dialog.setOnDismissListener()中调用，则必须跟踪按钮侦听器中是否已经调用了resume。

suspend fun displayDialog() = suspendCoroutine<String?> { continuation ->
    val builder = AlertDialog.Builder(context)
    builder.setCancelable(true)
    builder.setNegativeButton(android.R.string.cancel) { _, _ ->
        continuation.resume(null)
    }
    builder.setPositiveButton(android.R.string.ok) { _, _ ->
        continuation.resume("it's ok")
    }
    val dialog = builder.show()
    dialog.setOnDismissListener {
        // if the user clicked on OK, then resume has already been called
        // and we get an IllegalStateException
        continuation.resume(null)
    }
}

那么，跟踪resume是否已经被调用(以避免第二次调用它)，或者只是不去关心resume(null)调用(在onDismissListener中)是更好呢？

Answer 1

Continuation是一个低级原语，应该只恢复一次，所以您必须跟踪在使用它时是否已经调用了resume。或者，您可以使用更高级别的通信原语，例如具有多用途complete函数的CompletableDeferred：

suspend fun displayDialog(): String? {
    val deferred = CompletableDeferred<String?>()
    val builder = AlertDialog.Builder(context)
    builder.setCancelable(true)
    builder.setNegativeButton(android.R.string.cancel) { _, _ ->
        deferred.complete(null)
    }
    builder.setPositiveButton(android.R.string.ok) { _, _ ->
        deferred.complete("it's ok")
    }
    val dialog = builder.show()
    dialog.setOnDismissListener {
        deferred.complete(null)
    }
    return deferred.await()
}