我正在玩Reactive UI,我希望在完成一个过程后显示一条消息,并在一段时间(4秒)后隐藏此消息。如果消息的持续时间比隐藏时间快,则应重置超时,以便在显示/更新最后一条消息后4秒后始终隐藏消息。如果最后一条消息与之前的消息相同,也应该延长隐藏时间。
目前我有这个代码,它做了我想要的,但它看起来太麻烦了我。我只是尝试使用RxUI,所以大部分时间我都不知道自己在做什么。有没有更好的方法来实现这个目标?
public class MainViewModel: ReactiveObject
{
// Message to be shown.
private string message;
public string Message { get => message; set => this.RaiseAndSetIfChanged(ref message, value);
// Flag for the UI, if the message panel should be visible.
private ObservableAsPropertyHelper<bool> isMessageVisible;
public bool IsMessageVisible => isMessageVisible.Value;
// Command that runs async process, the result is the message to be shown.
public ReactiveCommand<Unit, string> Run { get; private set; }
public MainViewModel()
{
var msg = this.WhenAnyValue(x => x.Message, x => !string.IsNullOrEmpty(x));
// If message changes, after 4 seconds return false, causing hiding the message panel.
var hide = msg.Select(x => false).Throttle(TimeSpan.FromSeconds(4), RxApp.MainThreadScheduler);
// Merge both sequences into one output property.
Observable.Merge(msg, hide).ToProperty(this, x => x.IsMessageVisible, out isMessageVisible);
Run = ReactiveCommand.CreateFromObservable(() => Observable.StartAsync(Process));
// Merge various message sources and set message property. Set Message = null to force property change.
Observable.Merge(Run, Run.ThrownExceptions.Select(x => x.Message)).Subscribe(x => { Message = null; Message = x; });
}
...
}
答案 0 :(得分:4)
就个人而言,我这样声明isMessageVisible
:
isMessageVisible = this
.WhenAnyValue(x => x.Message, x => !string.IsNullOrEmpty(x))
.Select(showMessage => Observable.Return(showMessage).Concat(Observable.Return(false).Delay(4, RxApp.MainThreadScheduler)))
.Switch()
.ToProperty(this, x => x.IsMessageVisible);
它将所有逻辑放在一个管道中,我认为它更具可读性。
除了重写isMessageVisible
之外,我还会首先更改消息的显示方式。
我删除isMessageVisible
并且只拥有Message
属性。当string.IsNullOrEmpty(Message) == true
在用户界面中隐藏消息时,以及string.IsNullOrEmpty(Message) == false
显示用户界面时。这与RxUI绑定类似:
this.OneWayBind(ViewModel, vm => vm.Message, v => v.Message.Text, message => !string.IsNullOrWhitespace(message));
然后我在视图模型中执行此操作:
public class MainViewModel: ReactiveObject
{
// Message to be shown.
private ObservableAsPropertyHelper<string> message;
public string Message => message.Value;
// Command that runs async process, the result is the message to be shown.
public ReactiveCommand<Unit, string> Run { get; private set; }
public MainViewModel()
{
Run = ReactiveCommand.CreateFromObservable(() => Observable.StartAsync(Process));
// Merge various message sources and set message property.
message = Observable.Merge(Run, Run.ThrownExceptions.Select(x => x.Message))
.Select(msg => Observable.Return(msg).Concat(Observable.Return("").Delay(4, RxApp.MainThreadScheduler))) // 1
.Switch() // 2
.ToProperty(this, x => x.Message);
}
}
Select
返回的最新观察结果。如果发送了新消息,则先前的observable将不会发送空字符串如果您有多个命令返回消息,您可以添加一个便利功能来减少代码量:
private IObservable<string> CreateMessageStream(params ReactiveCommand<Unit, string> commands)
=> Observable.Merge(commands.SelectMany(command => new IObservable<string>[] { command, command.ThrownExceptions.Select(x => x.Message) }))
.Select(msg => Observable.Return(msg).Concat(Observable.Return("").Delay(4, RxApp.MainThreadScheduler)))
.Switch()
然后你可以像这样声明message
:
message = CreateMessageStream(Run, Walk, Crawl)
.ToProperty(this, x => x.Message);
Run
,Walk
和Crawl
都是ReactiveCommand
s。