问题描述
在 Dart 用户界面中，我有一个按钮 [提交] 来启动一个长异步请求.[submit] 处理程序返回一个 Future.接下来，按钮 [提交] 被按钮 [取消] 替换，以允许取消整个操作.在 [cancel] 处理程序中，我想取消长时间操作.如何取消提交处理程序返回的 Future?我没有找到这样做的方法.
In a Dart UI, I have a button [submit] to launch a long async request. The [submit] handler returns a Future. Next, the button [submit] is replaced by a button [cancel] to allow the cancellation of the whole operation. In the [cancel] handler, I would like to cancel the long operation. How can I cancel the Future returned by the submit handler? I found no method to do that.
推荐答案
据我所知，没有办法取消 Future.但是有一种方法可以取消 Stream 订阅，也许可以帮到您.
As far as I know, there isn't a way to cancel a Future. But there is a way to cancel a Stream subscription, and maybe that can help you.
在按钮上调用 onSubmit 会返回一个 StreamSubscription 对象.您可以显式存储该对象，然后对其调用 cancel() 以取消流订阅:
Calling onSubmit on a button returns a StreamSubscription object. You can explicitly store that object and then call cancel() on it to cancel the stream subscription:
StreamSubscription subscription = someDOMElement.onSubmit.listen((data) {
// you code here
if (someCondition == true) {
subscription.cancel();
}
});
稍后，作为对某些用户操作的回应，也许您可以取消订阅:
Later, as a response to some user action, perhaps, you can cancel the subscription:
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