Rx Show Loading（进度条或类似的东西）如果 Web 请求花费的时间太长

Question

我正在开发 Xamarin.Ios 小词典应用程序，它向服务器发送一个 GET 请求，它 returns 通过键（词）输入值，文本输入在 SearchBar 上，我在它的 TextChanged 上可以观察到事件，好事是我设法通过 observables 发送请求，但如果请求花费超过 1 或 2 秒，我想显示 LoadingView ......我尝试了 Buffer() 但它没有工作，所以这是代码谢谢!!

var dataStream = Observable.FromEventPattern<UISearchBarTextChangedEventArgs>(ev => searchBar.TextChanged += ev,
                        ev => searchBar.TextChanged -= ev)
    .Select(o => o.EventArgs.SearchText)
    .DistinctUntilChanged()
    .Throttle(TimeSpan.FromMilliseconds(300))
    .ObserveOn(SynchronizationContext.Current)
    .Select(t =>
    {
        #if DEBUG
            Console.WriteLine(t);
        #endif
        var instance = TranslateWebClient.Instance;//this is WebClient From where Get Request is made
        var data = instance.GetWordAsync(t);
        return data.ToObservable().ObserveOn(SynchronizationContext.Current);
    })
.Switch();

dataStream.Subscribe(o =>
{
    if (o == null || o.Count() == 0)
    {
        wordsTableView.DataSource = null;
        wordsTableView.ReloadData();
        return;
    }
    _words = o;
    initDataToUI();
}, ex =>
{
    if (ex is WebClient.NoInternetException)
    {
        //handle exception
    }
});

Answer 1

所以我认为这样的事情会奏效。添加此枚举，或使用类似的东西（如果可用）：

enum LoadState
{
    InitialState,
    RequestSent,
    ResponseLate,
    ResponseReceived
}

...然后将您的 dataStream 声明更改为以下内容：

var requestStream = Observable.FromEventPattern<UISearchBarTextChangedEventArgs>(ev => searchBar.TextChanged += ev,
                        ev => searchBar.TextChanged -= ev)
    .Select(o => o.EventArgs.SearchText)
    .DistinctUntilChanged()
    .Throttle(TimeSpan.FromMilliseconds(300))
    .ObserveOn(SynchronizationContext.Current)
    .Select(t =>
    {
#if DEBUG
        Console.WriteLine(t);
#endif
    var instance = TranslateWebClient.Instance;//this is WebClient From where Get Request is made
    var data = instance.GetWordAsync(t);
        return data.ToObservable().ObserveOn(SynchronizationContext.Current);
    })
    .Publish()
    .RefCount();

requestStream
    .SelectMany(o => Observable.Merge(
        Observable.Return(LoadState.RequestSent),
        Observable.Timer(TimeSpan.FromSeconds(1)).Select(_ => LoadState.ResponseLate),
        o.Select(_ => LoadState.ResponseReceived))
    )
    .Scan(LoadState.InitialState, 
        (previousState, newState) => previousState == LoadState.ResponseReceived && newState == LoadState.ResponseLate 
            ? LoadState.ResponseReceived 
            : newState
    )
    .Subscribe(state =>
    {
        if(state == LoadState.ResponseLate)
            ; //enable loading UI
        else
            ; //disable loading UI
    });

var dataStream = requestStream.Switch();

说明：requestStream 发出代表每个 Web 请求的可观察对象。我认为新的订阅符合你心目中的业务规则：当延迟达到 1 秒或更长时间时显示等待 UI，然后如果他们提出新请求或收到回复。

Rx Show Loading（进度条或类似的东西）如果 Web 请求花费的时间太长

Rx Show Loading(Progress Bar or something like that) If Web request takes too long

c#

reactive-programming

xamarin.ios

system.reactive

xamarin