本文講述如何實現(xiàn)控件的屬性如何可以被 Binding

官方例子

[RenderWith(typeof(_ActivityIndicatorRenderer))]
    public class ActivityIndicator : View, IElementConfiguration<ActivityIndicator>
    {
        //這就是值類型綁定的實現(xiàn)
        public static readonly BindableProperty IsRunningProperty = BindableProperty.Create
        ("IsRunning", typeof(bool), typeof(ActivityIndicator), default(bool));

        public static readonly BindableProperty ColorProperty = BindableProperty.Create
        ("Color", typeof(Color), typeof(ActivityIndicator), Color.Default);

        readonly Lazy<PlatformConfigurationRegistry<ActivityIndicator>> _platformConfigurationRegistry;

        public ActivityIndicator()
        {
            _platformConfigurationRegistry = new Lazy<PlatformConfigurationRegistry<ActivityIndicator>>(() => new PlatformConfigurationRegistry<ActivityIndicator>(this));
        }

        public Color Color
        {
            get { return (Color)GetValue(ColorProperty); }
            set { SetValue(ColorProperty, value); }
        }
        //與之對對應(yīng)的屬性
        public bool IsRunning
        {
            get { return (bool)GetValue(IsRunningProperty); }
            set { SetValue(IsRunningProperty, value); }
        }
        public IPlatformElementConfiguration<T, ActivityIndicator> On<T>() where T : IConfigPlatform
        {
            return _platformConfigurationRegistry.Value.On<T>();
        }
    }

Ps：這個官方例子是有問題的如输。

下面講一下如何綁定事件，其實 Xamarin Forms 綁定事件用的是 Command央勒，方法也不難不见。

public class MyEntry:Entry
{
    public ICommand MyCommand
    {
        get => (ICommand )GetValue(MyCommandProperty);
        set => SetValue(MyCommandProperty, value);
    }

    /// <summary>
    /// MyCommandProperty的Mvvm實現(xiàn)
    /// </summary>
    public static readonly BindableProperty MyCommandProperty = Create
    (
        nameof(回調(diào)方法),
        typeof(ICommand),
        typeof(MyEntry)
    ); //注意這里變量名的命名規(guī)則是MyCommand + Property，前者隨便崔步，后者固定語法

    private void 回調(diào)方法()
    {
        MyCommand?.Execute(null);
    }
}
//這樣這個MyEntry的MyCommand就可以被Mvvm綁定了稳吮。

用法：

View

<MyEntry MyCommand={ Binding ThisCommand ></MyEntry>

ViewModel

public class Model:某個mvvm框架的BasePage
{
    public Command ThisCommand
    {
        get
        {
            retrun new Command(()=>
            {
                //做點什么
            });
        }
    }
}