c# - Reactiveui 绑定(bind)不适用于 SeekBar.Progress

Question

我正在尝试学习 reactiveui，所以我想为 android 制作简单的小费计算器应用程序。 View 模型是:

public class TipCalcViewModel : ReactiveObject
{
    [IgnoreDataMember] private double _subtotal;

    [DataMember]
    public double Subtotal
    {
        get { return _subtotal; }
        set { this.RaiseAndSetIfChanged(ref _subtotal, value); }
    }

    [IgnoreDataMember] private int _percentage;

    [DataMember]
    public int Percentage
    {
        get { return _percentage; }
        set { this.RaiseAndSetIfChanged(ref _percentage, value); }
    }

    [IgnoreDataMember] private readonly ObservableAsPropertyHelper<double> _tipAmount;

    [DataMember]
    public double TipAmount
    {
        get { return _tipAmount.Value; }
    }

    [IgnoreDataMember] private readonly ObservableAsPropertyHelper<double> _total;

    [DataMember]
    public double Total
    {
        get { return _total.Value; }
    }

    public TipCalcViewModel(ITipCalcService service)
    {
        _tipAmount = this.WhenAnyValue(
            x => x.Subtotal,
            y => y.Percentage,
            service.CalculateTipAmount)
            .ToProperty(this, vm => vm.TipAmount);

        _total = this.WhenAnyValue(
            x => x.Subtotal,
            y => y.Percentage,
            service.CalculateTotal)
            .ToProperty(this, vm => vm.Total);
    }
}

Activity 看起来像这样:

public class TipCalcActivity : ReactiveActivity<TipCalcViewModel>
{
    public EditText SubTotal { get { return this.GetControl<EditText>(); } }
    public SeekBar Percentage { get { return this.GetControl<SeekBar>(); } }
    public TextView PercentageText { get { return this.GetControl<TextView>(); } }
    public TextView TipAmount { get { return this.GetControl<TextView>(); } }
    public TextView Total { get { return this.GetControl<TextView>(); } }

    protected override void OnCreate(Bundle bundle)
    {
        base.OnCreate(bundle);

        // Set our view from the "main" layout resource
        SetContentView(Resource.Layout.Main);
        var service = new TipCalcService();
        ViewModel = new TipCalcViewModel(service);

        this.Bind(ViewModel, vm => vm.Subtotal, v => v.SubTotal.Text);
        //this.Bind(ViewModel, vm => vm.Percentage, v => v.Percentage.Progress);
        this.OneWayBind(ViewModel, vm => vm.Percentage, v => v.PercentageText.Text);
        this.OneWayBind(ViewModel, vm => vm.TipAmount, v => v.TipAmount.Text);
        this.OneWayBind(ViewModel, vm => vm.Total, v => v.Total.Text);

        var disposable = Observable.FromEventPattern<SeekBar.ProgressChangedEventArgs>(
            h => Percentage.ProgressChanged += h,
            h => Percentage.ProgressChanged -= h)
            .Throttle(TimeSpan.FromMilliseconds(500))
            .DistinctUntilChanged()
            .ObserveOn(RxApp.MainThreadScheduler)
            .Subscribe(x => 
                ViewModel.Percentage = x.EventArgs.Progress);
    }
}

所以问题:

• 如果我使用上面注释的绑定(bind)，则不会发生任何事情。因此 progress 属性正在正确更改，但从未设置 ViewModel 的 Percentage 属性。绑定(bind)从 View 模型到 View 工作，但不是其他方式(EditText 绑定(bind)在两个方向上都工作正常)。如何解决这个问题？

• 如果我从 ProgressChanged 事件创建可观察对象，我设法让它工作。但即使我不得不做这样的事情，我也不确定这是否是正确的方法。另外，当 Activity 被手动销毁时，我是否必须处理订阅？

• 最后一件事。如果我想学习这个框架，最好的开始方式是什么？

Answer 1

SeekBar 很可能不在受支持的现成控件列表中； Android 没有内置的方式来观察 View 属性，因此我们必须将它们硬编码为一次性的。如果您编写类似以下内容，则可以完成这项工作:

var progressChanged = Observable.FromEventPattern<SeekBar.ProgressChangedEventArgs>(
        h => Percentage.ProgressChanged += h,
        h => Percentage.ProgressChanged -= h);

this.Bind(ViewModel, 
    vm => vm.Percentage, 
    v => v.Percentage.Progress, 
    signalViewUpdate: progressChanged);