XamlCompositionBrushBase 類別

定義

public ref class XamlCompositionBrushBase : Brush

/// [Windows.Foundation.Metadata.ContractVersion(Microsoft.UI.Xaml.WinUIContract, 65536)]
/// [Windows.Foundation.Metadata.MarshalingBehavior(Windows.Foundation.Metadata.MarshalingType.Agile)]
/// [Windows.Foundation.Metadata.Threading(Windows.Foundation.Metadata.ThreadingModel.Both)]
class XamlCompositionBrushBase : Brush

[Windows.Foundation.Metadata.ContractVersion(typeof(Microsoft.UI.Xaml.WinUIContract), 65536)]
[Windows.Foundation.Metadata.MarshalingBehavior(Windows.Foundation.Metadata.MarshalingType.Agile)]
[Windows.Foundation.Metadata.Threading(Windows.Foundation.Metadata.ThreadingModel.Both)]
public class XamlCompositionBrushBase : Brush

Public Class XamlCompositionBrushBase
Inherits Brush

繼承

Object Platform::Object IInspectable DependencyObject Brush XamlCompositionBrushBase

衍生

Microsoft.UI.Xaml.Media.AcrylicBrush

Microsoft.UI.Xaml.Media.RadialGradientBrush

Microsoft.UI.Xaml.Media.RevealBrush

屬性

ContractVersionAttribute MarshalingBehaviorAttribute ThreadingAttribute

範例

這個範例展示了一個自訂畫筆的定義，該筆刷會用 Win2D 模糊效果和 CompositionBackdropBrush 套用 UIElement 後方的模糊複製品：

public sealed class BackdropBlurBrush : XamlCompositionBrushBase
{
    public static readonly DependencyProperty BlurAmountProperty = DependencyProperty.Register(
        "BlurAmount",
        typeof(double),
        typeof(BackdropBlurBrush),
        new PropertyMetadata(0.0, new PropertyChangedCallback(OnBlurAmountChanged)
        )
    );

    public double BlurAmount
    {
        get { return (double)GetValue(BlurAmountProperty); }
        set { SetValue(BlurAmountProperty, value); }
    }

    private static void OnBlurAmountChanged(DependencyObject d, DependencyPropertyChangedEventArgs e)
    {
        var brush = (BackdropBlurBrush)d;
        // Unbox and set a new blur amount if the CompositionBrush exists.
        brush.CompositionBrush?.Properties.InsertScalar("Blur.BlurAmount", (float)(double)e.NewValue);            
    }

    public BackdropBlurBrush()
    {
    }

    protected override void OnConnected()
    {
        // Delay creating composition resources until they're required.
        if (CompositionBrush == null)
        {
            var backdrop = Window.Current.Compositor.CreateBackdropBrush();                

            // Use a Win2D blur affect applied to a CompositionBackdropBrush.
            var graphicsEffect = new GaussianBlurEffect
            {
                Name = "Blur",
                BlurAmount = (float)this.BlurAmount,
                Source = new CompositionEffectSourceParameter("backdrop")
            };

            var effectFactory = Window.Current.Compositor.CreateEffectFactory(graphicsEffect, new[] { "Blur.BlurAmount" });
            var effectBrush = effectFactory.CreateBrush();

            effectBrush.SetSourceParameter("backdrop", backdrop);

            CompositionBrush = effectBrush;
        }
    }

    protected override void OnDisconnected()
    {
        // Dispose of composition resources when no longer in use.
        if (CompositionBrush != null)
        {
            CompositionBrush.Dispose();
            CompositionBrush = null;
        }
    }
}

以下的 C++/WinRT 程式碼範例中，你需要在專案中新增一個 Midl 檔案（.idl）。

// BackdropBlurBrush.idl
namespace MyApp
{
    [default_interface]
    runtimeclass BackdropBlurBrush : Windows.UI.Xaml.Media.XamlCompositionBrushBase
    {
        BackdropBlurBrush();
        static Windows.UI.Xaml.DependencyProperty BlurAmountProperty{ get; };
        Double BlurAmount;
    }
}

// pch.h
// You'll need to install the Microsoft Win2D NuGet package for this code example.
#include <winrt/Microsoft.Graphics.Canvas.Effects.h>
#include <winrt/Windows.Graphics.Effects.h>

// BackdropBlurBrush.h.
struct BackdropBlurBrush : BackdropBlurBrushT<BackdropBlurBrush>
{
    BackdropBlurBrush() = default;

    static Windows::UI::Xaml::DependencyProperty BlurAmountProperty() { return m_blurAmountProperty; }

    double BlurAmount()
    {
        return winrt::unbox_value<double>(GetValue(m_blurAmountProperty));
    }

    void BlurAmount(double value)
    {
        SetValue(m_blurAmountProperty, winrt::box_value(value));
    }

    void OnConnected();
    void OnDisconnected();

    static void OnBlurAmountChanged(Windows::UI::Xaml::DependencyObject const& d, Windows::UI::Xaml::DependencyPropertyChangedEventArgs const& e);

private:
    static Windows::UI::Xaml::DependencyProperty m_blurAmountProperty;
};

// WindowBlurBrush.cpp.
Windows::UI::Xaml::DependencyProperty BackdropBlurBrush::m_blurAmountProperty =
    Windows::UI::Xaml::DependencyProperty::Register(
        L"BlurAmount",
        winrt::xaml_typename<double>(),
        winrt::xaml_typename<MyApp::BackdropBlurBrush>(),
        Windows::UI::Xaml::PropertyMetadata{ winrt::box_value(0.), Windows::UI::Xaml::PropertyChangedCallback{ &BackdropBlurBrush::OnBlurAmountChanged } }
);

void BackdropBlurBrush::OnBlurAmountChanged(Windows::UI::Xaml::DependencyObject const& d, Windows::UI::Xaml::DependencyPropertyChangedEventArgs const& e)
{
    auto brush{ d.as<MyApp::BackdropBlurBrush>() };
    // Unbox and set a new blur amount if the CompositionBrush exists.
    if (brush.CompositionBrush() != nullptr)
    {
        brush.CompositionBrush().Properties().InsertScalar(L"Blur.BlurAmount", (float)winrt::unbox_value<double>(e.NewValue()));
    }
}

void BackdropBlurBrush::OnConnected()
{
    // Delay creating composition resources until they're required.
    if (!CompositionBrush())
    {
        auto backdrop{ Windows::UI::Xaml::Window::Current().Compositor().CreateBackdropBrush() };

        // Use a Win2D blur affect applied to a CompositionBackdropBrush.
        Microsoft::Graphics::Canvas::Effects::GaussianBlurEffect graphicsEffect{};
        graphicsEffect.Name(L"Blur");
        graphicsEffect.BlurAmount(this->BlurAmount());
        graphicsEffect.Source(Windows::UI::Composition::CompositionEffectSourceParameter(L"backdrop"));

        auto effectFactory{ Windows::UI::Xaml::Window::Current().Compositor().CreateEffectFactory(graphicsEffect, { L"Blur.BlurAmount" }) };
        auto effectBrush{ effectFactory.CreateBrush() };

        effectBrush.SetSourceParameter(L"backdrop", backdrop);

        CompositionBrush(effectBrush);
    }
}

void BackdropBlurBrush::OnDisconnected()
{
    // Dispose of composition resources when no longer in use.
    if (CompositionBrush())
    {
        CompositionBrush(nullptr);
    }
}

// WindowBlurBrush.h:
public ref class BackdropBlurBrush sealed :
    public Windows::UI::Xaml::Media::XamlCompositionBrushBase
{
public:
    BackdropBlurBrush();

    static property Windows::UI::Xaml::DependencyProperty^ BlurAmountProperty
    {
        Windows::UI::Xaml::DependencyProperty^ get() { return m_blurAmountProperty; }
    };

    property double BlurAmount
    {
        double get() 
        {
            return static_cast<double>(GetValue(BlurAmountProperty));
        }
        void set(double value) 
        {
            SetValue(BlurAmountProperty, value);
        }
    };

protected:
    virtual void OnConnected() override;
    virtual void OnDisconnected() override;	
    private:
    static Windows::UI::Xaml::DependencyProperty^ m_blurAmountProperty;
    static void OnBlurAmountChanged(Windows::UI::Xaml::DependencyObject^ d, Windows::UI::Xaml::DependencyPropertyChangedEventArgs^ e);
};

// WindowBlurBrush.cpp:
DependencyProperty^ BackdropBlurBrush::m_blurAmountProperty = DependencyProperty::Register(
    "BlurAmount",
    Platform::String::typeid,
    BackdropBlurBrush::typeid,
    ref new PropertyMetadata(0.0, ref new PropertyChangedCallback(OnBlurAmountChanged))
);

BackdropBlurBrush::BackdropBlurBrush()
{
}

void BackdropBlurBrush::OnBlurAmountChanged(DependencyObject^ d, DependencyPropertyChangedEventArgs^ e)
{
    auto brush = static_cast<BackdropBlurBrush^>(d);
    // Unbox and set a new blur amount if the CompositionBrush exists
    if (brush->CompositionBrush != nullptr)
    {
        brush->CompositionBrush->Properties->InsertScalar("Blur.BlurAmount", (float)static_cast<double>(e->NewValue));
    }
}

void BackdropBlurBrush::OnConnected()
{
    // Delay creating composition resources until they're required
    if (CompositionBrush == nullptr)
    {
        auto backdrop = Window::Current->Compositor->CreateBackdropBrush();

        // Use a Win2D blur affect applied to a CompositionBackdropBrush
        auto graphicsEffect = ref new GaussianBlurEffect();
        graphicsEffect->Name = "Blur";
        graphicsEffect->BlurAmount = static_cast<float>(this->BlurAmount);
        graphicsEffect->Source = ref new CompositionEffectSourceParameter("backdrop");

        auto animatableProperties = ref new Platform::Collections::Vector<Platform::String^>();
        animatableProperties->Append("Blur.BlurAmount");

        auto effectFactory = Window::Current->Compositor->CreateEffectFactory(graphicsEffect, animatableProperties);
        auto effectBrush = effectFactory->CreateBrush();

        effectBrush->SetSourceParameter("backdrop", backdrop);

        CompositionBrush = effectBrush;
    }
}

void BackdropBlurBrush::OnDisconnected()
{
    // Dispose of composition resources when no longer in use
    if (CompositionBrush != nullptr)
    {
        delete CompositionBrush;
        CompositionBrush = nullptr;
    }
}

上述筆刷可以像其他 XAML 筆刷類型一樣用於繪製 UIElement，例如：

對於 C++/WinRT，也要加上 #include "BackdropBlurBrush.h"MainPage.h。

<Ellipse Width="100" Height="100">
    <Ellipse.Fill>
        <local:BackdropBlurBrush BlurAmount="10" />
    </Ellipse.Fill>
</Ellipse>

備註

你可以使用 XamlCompositionBrushBase 來建立自訂筆刷。

例如，它可以用來建立一個刷子，使用 CompositionEffectBrush 為 XAML UIElement 套用效果，或用 SceneLightingEffect 控制被 XamlLight 照亮時元素的反射特性，或是將一連串效果串連起來，產生更複雜的效果。

在製作畫筆時，通常建議等到畫筆被使用時再開始製作 CompositionBrush 及相關資源。 OnConnected 方法是在螢幕上首次使用筆刷來繪製元素時呼叫，因此你可以覆寫 OnConnected ，只在需要時安全建立資源。 這表示你可以在 ResourceDictionary 中建立一個筆刷實例，然後再從 UI 定義的其他部分引用該筆刷資源，只有在筆刷實際使用時才支付創建合成資源的成本。

當作文資源不再使用時，處理掉它們也是個好習慣。 當畫面上某個刷子實例不再使用時，會呼叫 OnDisconnected 方法，這樣你可以覆寫 OnDisconnected 來安全地處理資源。 如果刷子在斷開後又被使用，則會再次呼叫 OnConnected 。

另請參閱

• 使用 XAML 筆刷
• 使用 XAML 的合成視覺圖層
• 構圖筆刷