Jaa

ImageButton Drop Shadows on Android

  • Artikkeli

This Android platform-specific is used to enable a drop shadow on a ImageButton. It's consumed in XAML by setting the ImageButton.IsShadowEnabled bindable property to true, along with a number of additional optional bindable properties that control the drop shadow:

<ContentPage ...
             xmlns:android="clr-namespace:Xamarin.Forms.PlatformConfiguration.AndroidSpecific;assembly=Xamarin.Forms.Core">
    <StackLayout Margin="20">
       <ImageButton ...
                    Source="XamarinLogo.png"
                    BackgroundColor="GhostWhite"
                    android:ImageButton.IsShadowEnabled="true"
                    android:ImageButton.ShadowColor="Gray"
                    android:ImageButton.ShadowRadius="12">
            <android:ImageButton.ShadowOffset>
                <Size>
                    <x:Arguments>
                        <x:Double>10</x:Double>
                        <x:Double>10</x:Double>
                    </x:Arguments>
                </Size>
            </android:ImageButton.ShadowOffset>
        </ImageButton>
        ...
    </StackLayout>
</ContentPage>

Alternatively, it can be consumed from C# using the fluent API:

using Xamarin.Forms.PlatformConfiguration;
using Xamarin.Forms.PlatformConfiguration.AndroidSpecific;
...

var imageButton = new Xamarin.Forms.ImageButton { Source = "XamarinLogo.png", BackgroundColor = Color.GhostWhite, ... };
imageButton.On<Android>()
           .SetIsShadowEnabled(true)
           .SetShadowColor(Color.Gray)
           .SetShadowOffset(new Size(10, 10))
           .SetShadowRadius(12);

Important

A drop shadow is drawn as part of the ImageButton background, and the background is only drawn if the BackgroundColor property is set. Therefore, a drop shadow will not be drawn if the ImageButton.BackgroundColor property isn't set.

The ImageButton.On<Android> method specifies that this platform-specific will only run on Android. The ImageButton.SetIsShadowEnabled method, in the Xamarin.Forms.PlatformConfiguration.AndroidSpecific namespace, is used to control whether a drop shadow is enabled on the ImageButton. In addition, the following methods can be invoked to control the drop shadow:

  • SetShadowColor – sets the color of the drop shadow. The default color is Color.Default.
  • SetShadowOffset – sets the offset of the drop shadow. The offset changes the direction the shadow is cast, and is specified as a Size value. The Size structure values are expressed in device-independent units, with the first value being the distance to the left (negative value) or right (positive value), and the second value being the distance above (negative value) or below (positive value). The default value of this property is (0.0, 0.0), which results in the shadow being cast around every side of the ImageButton.
  • SetShadowRadius– sets the blur radius used to render the drop shadow. The default radius value is 10.0.

Note

The state of a drop shadow can be queried by calling the GetIsShadowEnabled, GetShadowColor, GetShadowOffset, and GetShadowRadius methods.

The result is that a drop shadow can be enabled on a ImageButton:

ImageButton with drop shadow