从视图设置时自定义控件可绑定属性未命中

Question

我创建了一个控件，它有一个可绑定的属性，但是当我尝试设置它的值时，它没有设置，当我检查它的设置器时，它在调试时没有被命中，不确定我做错了什么。

public decimal MetricValue
        {
            get => (decimal)GetValue(MetricValueProperty);
            set => SetValue(MetricValueProperty, value);
        }

        public static readonly BindableProperty MetricValueProperty =
            BindableProperty.Create(
                propertyName: nameof(MetricValue),
                returnType: typeof(decimal),
                declaringType: typeof(HeightSelection),
                defaultBindingMode: BindingMode.TwoWay,
                propertyChanged: MetricValuePropertyChanged);

我也有一个 propertychanged，它没有被提升

 <controls:customControl
                                        CurrentSystemOfMeasure="{Binding CurrentSystemOfMeasure}"
                                        MetricValue="{Binding CurrentHeight}"
                                        TextAlignment="Start"
                                        OnHeightSelectedCommand="{Binding HeightSelectionCommand}"
                                        IsValid="True" />

任何输入都会有所帮助

Answer 1

您是否在 xaml 视图中设置了上下文？

这是我的方式：

 public static readonly BindableProperty CancelButtonVisibleAvailableProperty = BindableProperty.Create(
        propertyName: "CancelButtonVisible",
        returnType: typeof(bool),
        declaringType: typeof(SelphiDetailPhotosView),
        defaultValue: true);

    public bool CancelButtonVisible
    {
        get { return (bool)GetValue(CancelButtonVisibleAvailableProperty); }
        set { SetValue(CancelButtonVisibleAvailableProperty, value); }
    }

ContentView 需要 ax:name 在属性 IsVisible 中设置上下文在您的情况下，您需要在 label 的 Text 属性中设置上下文以显示十进制值

我已经设置了引用我的自定义视图selphiDetailPhotosView的上下文

   <Button IsVisible="{Binding Source={x:Reference selphiDetailPhotosView}, Path=CancelButtonVisible}"
                        Margin="27,0,27,18"
                        BackgroundColor="{StaticResource PlatinumColor}"
                        Command="{Binding CancelCommand}"
                        Text="Cancelar"
                        TextColor="White"
                        TextTransform="None" />



<ContentView
xmlns="http://xamarin.com/schemas/2014/forms"
xmlns:x="http://schemas.microsoft.com/winfx/2009/xaml"
x:Class="confia.Views.Views.OnBoardingAndLivenessSharedViews.SelphiDetailPhotosView"
   xmlns:svg="clr-namespace:FFImageLoading.Svg.Forms;assembly=FFImageLoading.Svg.Forms"
xmlns:transformation="clr-namespace:FFImageLoading.Transformations;assembly=FFImageLoading.Transformations"
xmlns:views="clr-namespace:confia.Views.Views"
  xmlns:converters="clr-namespace:confia.Views.Converters"
x:Name="selphiDetailPhotosView"
>

最后在您的 ContentPage 中调用您的自定义控件并与您的 ViewModel 绑定

<customControl:SelphiDetailPhotosView CancelButtonVisible="{Binding CanCancel}"/>

Answer 2

我已经复制了你的场景，这对我有用。

CodeBehind 自定义控件

 public partial class CustomControl : ContentView
{
    public CustomControl()
    {
        InitializeComponent();
    }

    public static readonly BindableProperty MetricValueProperty = BindableProperty.Create(
       propertyName: nameof(MetricValue),
       returnType: typeof(decimal),
       declaringType: typeof(CustomControl),
       defaultBindingMode: BindingMode.TwoWay,
       defaultValue: 0m);

    public decimal MetricValue
    {
        get { return (decimal)this.GetValue(MetricValueProperty); }
        set { this.SetValue(MetricValueProperty, value); }
    }
}

CustomControl Xaml

<ContentView
xmlns="http://xamarin.com/schemas/2014/forms"
xmlns:x="http://schemas.microsoft.com/winfx/2009/xaml"
x:Class="ferreplace.Views.Controls.CustomControl"
x:Name="this"
>
<ContentView.Content>
    <StackLayout HorizontalOptions="CenterAndExpand" >
        <Label Text="Metric Value" FontSize="40"/>
        <Label FontSize="20" Text="{Binding Source={x:Reference  this}, Path=MetricValue}" ></Label>
    </StackLayout>
</ContentView.Content>

ContentPage 调用自定义控件

<ContentPage xmlns="http://xamarin.com/schemas/2014/forms"
             xmlns:x="http://schemas.microsoft.com/winfx/2009/xaml"
             xmlns:controls="clr-namespace:ferreplace.Views.Controls"
             x:Class="ferreplace.MainPage">
 <StackLayout>
      <controls:CustomControl MetricValue="{Binding MetricValueBinding}"/>
    </StackLayout>
</ContentPage>

视图模型

 public class MainPageViewModel: BindableBase, IInitializeAsync
{

    private decimal _metricValueBinding;
    public decimal MetricValueBinding
    {
        get
        {
            return _metricValueBinding;
        }
        set
        {
            SetProperty(ref _metricValueBinding, value);
        }
    }

    public MainPageViewModel()
    {
    }

    public async Task InitializeAsync(INavigationParameters parameters)
    {
        MetricValueBinding = 30m;
    }
}

十进制绑定结果也许您在可绑定属性创建中忘记了默认值