我正在尝试 Hook 流 (IObservable
),以便在 UWP 项目中通过 ToggleSwitch
进行控制。期望是当开关处于 On
状态时我开始流式传输,并在它处于 Off
状态时停止。
所以想到的是
1. 创建两个命令,一个启动流,另一个停止流。
2. 创建两个 Observable,用于监视开关状态和条件合适时的 InvokeCommand
。
View 模型
public class MainPageViewModel : ViewModelBase
{
public ReactiveCommand<Unit, (long, float)> StreamCommand { get; }
public ReactiveCommand<Unit, Unit> StopCommand { get; }
public IObservable<(long, float)> FlowStream { get; set; }
private bool _isStreamOn;
public bool IsStreamOn
{
get => _isStreamOn;
set => this.RaiseAndSetIfChanged(ref _isStreamOn, value);
}
public MainPageViewModel()
{
var stream = GetStream();
var canSwitchOn = this.WhenAnyValue(x => x.IsStreamOn);
var canSwitchOff = this.WhenAnyValue(x => x.IsStreamOn, isOn => isOn != true);
FlowStream = StreamCommand = ReactiveCommand.CreateFromObservable(
() =>
{
stream.Start();
return Observable.FromEventPattern<StreamDataEventArgs<(long, INumeric, INumeric, INumeric)>>(
h => stream.DataAvailable += h,
h => stream.DataAvailable -= h)
.SelectMany(e => e.EventArgs.Data)
.Select(item => item));
}, canSwitchOn);
StopCommand = ReactiveCommand.Create(
() =>
{
stream.Stop();
IsStreamOn = false;
}, canSwitchOff);
canSwitchOff.InvokeCommand(StopCommand);
canSwitchOn.InvokeCommand(StreamCommand);
}
}
查看
public sealed partial class MainPage : Page, IViewFor<MainPageViewModel>
{
public MainPage()
{
InitializeComponent();
NavigationCacheMode = Windows.UI.Xaml.Navigation.NavigationCacheMode.Enabled;
ViewModel = new MainPageViewModel();
this.WhenActivated(subscription =>
{
subscription(this.OneWayBind(this.ViewModel,
vm => vm.StreamCommand,
v => v.chart.SeriesCollection[0].Stream)); // Chart take care of displaying data
subscription(this.Bind(this.ViewModel,
vm => vm.IsStreamOn,
v => v.streamToggle.IsOn));
});
}
object IViewFor.ViewModel
{
get { return ViewModel; }
set { ViewModel = (MainPageViewModel)value; }
}
public MainPageViewModel ViewModel
{
get { return (MainPageViewModel)GetValue(ViewModelProperty); }
set { SetValue(ViewModelProperty, value); }
}
public static readonly DependencyProperty ViewModelProperty =
DependencyProperty.Register("ViewModel", typeof(MainPageViewModel), typeof(MainPage), null);
}
但是,InvokeCommand
失败了,因为它需要 ReactiveCommands 获取 bool 值,而不是 Unit
。
知道如何在满足特定条件时调用命令吗?
最佳答案
如果您想根据 IObservable<(long, float)> FlowStream
打开和关闭流 ( IObservable<bool> IsStreamOn
) observable 那么你可以这样做:
IObservable<(long, float)> outputStream =
IsStreamOn
.Select(flag => flag ? FlowStream : Observable.Never<(long, float)>())
.Switch();
所以每次IsStreamOn
产生 true
你开始从 FlowStream
获取值,否则值停止。
这假设FlowStream
火爆。如果没有,请执行以下操作:
IObservable<(long, float)> outputStream =
FlowStream
.Publish(fs =>
IsStreamOn
.Select(flag => flag ? fs : Observable.Never<(long, float)>())
.Switch());
这是一个简单的测试:
void Main()
{
IObservable<long> outputStream =
FlowStream
.Publish(fs =>
IsStreamOn
.Select(flag => flag ? fs : Observable.Never<long>())
.Switch());
using (outputStream.Subscribe(Console.WriteLine))
{
IsStreamOn.OnNext(true);
Thread.Sleep(TimeSpan.FromSeconds(2.5));
IsStreamOn.OnNext(false);
Thread.Sleep(TimeSpan.FromSeconds(3.0));
IsStreamOn.OnNext(true);
Thread.Sleep(TimeSpan.FromSeconds(3.0));
}
}
IObservable<long> FlowStream = Observable.Interval(TimeSpan.FromSeconds(1.0));
Subject<bool> IsStreamOn = new Subject<bool>();
这会产生:
0 1 5 6 7
Given the comments re actually calling .Start()
and .Stop()
then try something like this:
IObservable<(long, float)> outputStream =
Observable
.Create<(long, float)>(o =>
{
var stream = GetStream();
return
FlowStream
.Publish(fs =>
IsStreamOn
.Do(flag => { if (flag) stream.Start(); else stream.Stop(); })
.Select(flag => flag ? fs : Observable.Never<(long, float)>())
.Switch())
.Subscribe(o);
});
关于mvvm - 使用 ReactiveUI 通过 ToggleSwitch 控制(启动/停止)IObservable,我们在Stack Overflow上找到一个类似的问题: https://stackoverflow.com/questions/46398628/