c# - 将绑定(bind)值设置为 Xamarin Forms 中行为的参数

Question

如何在 Xamarin Forms 中将绑定(bind)值设置为行为的参数？

当我这样做时，我得到:错误。找不到“InputValue”的属性、可绑定(bind)属性或事件，或者值和属性之间的类型不匹配。

XAML:

<Label Grid.Column="0" x:Name="player" FontSize="Small" VerticalOptions="CenterAndExpand" HorizontalOptions="CenterAndExpand"
                                       Text="{Binding FormattedName}" >
                                    <Label.Behaviors>
                                        <local:ColorTextLabelBehavior MaxInputValue="100" MinInputValue="0" InputValue="{Binding Happiness}" />
                                    </Label.Behaviors>
                                </Label>

C#:

public class ColorTextLabelBehavior : Behavior<Label>
{
    public static readonly BindableProperty MaxValue = BindableProperty.Create("MaxValue", typeof(int), typeof(ColorTextLabelBehavior), defaultValue: 100);
    public static readonly BindableProperty MinValue = BindableProperty.Create("MinValue", typeof(int), typeof(ColorTextLabelBehavior), defaultValue: 0);
    public static readonly BindableProperty ActualValue = BindableProperty.Create("ActualValue", typeof(int), typeof(ColorTextLabelBehavior), defaultValue: 100);

    public int MaxInputValue
    {
        get { return (int)GetValue(MaxValue); }
        set { SetValue(MaxValue, value); }
    }
    public int MinInputValue
    {
        get { return (int)GetValue(MinValue); }
        set { SetValue(MinValue, value); }
    }
    public int InputValue
    {
        get { return (int)GetValue(ActualValue); }
        set { SetValue(ActualValue, value); }
    }

    void HandleTextChanged(object sender, PropertyChangedEventArgs e)
    {
        try
        {
            float percent = ((float)InputValue - (float)MinInputValue) / ((float)MaxInputValue - (float)MinInputValue);
            double resultRed = Color.Red.R + percent * (Color.Green.R - Color.Red.R);
            double resultGreen = Color.Red.G + percent * (Color.Green.G - Color.Red.G);
            double resultBlue = Color.Red.B + percent * (Color.Green.B - Color.Red.B);
            ((Label)sender).TextColor = new Color(resultRed, resultGreen, resultBlue);
        }
        catch (Exception)
        {

        }
    }

    protected override void OnAttachedTo(BindableObject bindable)
    {
        bindable.PropertyChanged += HandleTextChanged;
    }

    protected override void OnDetachingFrom(BindableObject bindable)
    {
        bindable.PropertyChanged += HandleTextChanged;
    }
}

如果我对“InputValue”的值进行硬编码，这是可行的，但我希望能够发送绑定(bind)，以便它自动为文本着色。

请注意，如果重要的话，这是在 ListView 中。

请帮忙，我一直坚持这个，找不到任何答案。我也愿意接受其他实现方案。

谢谢!!

Answer 1

我认为准确的命名很重要，BindableProperty 必须在实际属性的名称末尾附加“Property”。来自docs :

The naming convention for bindable properties is that the bindable property identifier must match the property name specified in the Create method, with "Property" appended to it.

所以我相信你想要这样的东西:

public static readonly BindableProperty MaxInputValueProperty = BindableProperty.Create(nameof(MaxInputValue), typeof(int), typeof(ColorTextLabelBehavior), defaultValue: 100);
public static readonly BindableProperty MinInputValueProperty = BindableProperty.Create(nameof(MinInputValue), typeof(int), typeof(ColorTextLabelBehavior), defaultValue: 0);
public static readonly BindableProperty InputValueProperty = BindableProperty.Create(nameof(InputValue), typeof(int), typeof(ColorTextLabelBehavior), defaultValue: 100);

public int MaxInputValue
{
    get { return (int)GetValue(MaxValue); }
    set { SetValue(MaxValue, value); }
}
public int MinInputValue
{
    get { return (int)GetValue(MinValue); }
    set { SetValue(MinValue, value); }
}
public int InputValue
{
    get { return (int)GetValue(ActualValue); }
    set { SetValue(ActualValue, value); }
}