自定义控件公开子Binadable属性

Question

The situation is the following:

I have created a custom control which contains among other children a ImageView. I want to be able to bind a property (IsVisible) of this child view from XAML when using the custom control but am not sure how I can expose this property in the parent custom control.

I want to set something like this (where IsLeftImageVisible should be the exposed child control property):

<controls:StepIndicator IsLeftImageVisible="{Binding IsValid}" />

For now i've done something like this, but I don't really like it:

public static readonly BindableProperty IsLeftButtonVisibleProperty = 
    BindableProperty.Create<StepIndicator, bool>
       (x => x.IsLeftImageVisible, true, propertyChanged: ((
        bindable, value, newValue) =>
    {
        var control = (StepIndicator)bindable;
        control.ImageLeft.IsVisible = newValue;
    }));

    public bool IsLeftImageVisible
    {
        get { return (bool)GetValue(IsLeftImageVisibleProperty); }
        set { SetValue(IsLeftImageVisibleProperty, value); }
    }

Is there a way to do this more elgantly?

Answer 1

Alternative way of doing this:

• Change LeftImage to private field
• Use OnElementPropertyChanged (from renderer) or OnPropertyChanged (from shared class)

From renderer:

protected override void OnElementPropertyChanged(object sender, PropertyChangedEventArgs e)
{
    if (e.PropertyName == StepIndicator.IsLeftButtonVisibleProperty.PropertyName)
    {
        // do something
    }
}

From shared class:

protected override void OnPropertyChanged(string propertyName)
{
    base.OnPropertyChanged(propertyName);
    if (propertyName == StepIndicator.IsLeftButtonVisibleProperty.PropertyName)
    {
        this.imageLeft.IsVisible = newValue;
    }
}

Or subscribe to PropertyChanged event:

PropertyChanged += (sender, e) => {
    if (e.PropertyName == StepIndicator.IsLeftButtonVisibleProperty.PropertyName) { // do something }
};