EN
Este conteúdo não está disponível em seu idioma, mas aqui está a versão em inglês.

LinearGradientBrush class

Applies to Windows and Windows Phone

Paints an area with a linear gradient.

Inheritance

Object
  DependencyObject
    Brush
      GradientBrush
        LinearGradientBrush

Syntax


public sealed class LinearGradientBrush : GradientBrush


<LinearGradientBrush ...>
  oneOrMoreGradientStops
</LinearGradientBrush

XAML Values

oneOrMoreGradientStops

One or more GradientStop object elements. Object elements defined here become members of the collection when code accesses the GradientStops property at run time.

Attributes

[MarshalingBehavior(Agile)]
[Threading(Both)]
[Version(0x06020000)]
[WebHostHidden()]

Members

The LinearGradientBrush class has these types of members:

Constructors

The LinearGradientBrush class has these constructors.

ConstructorDescription
LinearGradientBrush() Initializes a new instance of the LinearGradientBrush class.
LinearGradientBrush(GradientStopCollection, Double) Initializes a new instance of the LinearGradientBrush class that has the specified GradientStopCollection and angle.

 

Methods

The LinearGradientBrush class has these methods. It also inherits methods from the Object class.

MethodDescription
ClearValue Clears the local value of a dependency property. (Inherited from DependencyObject)
GetAnimationBaseValue Returns any base value established for a dependency property, which would apply in cases where an animation is not active. (Inherited from DependencyObject)
GetValue Returns the current effective value of a dependency property from a DependencyObject. (Inherited from DependencyObject)
ReadLocalValue Returns the local value of a dependency property, if a local value is set. (Inherited from DependencyObject)
SetValue Sets the local value of a dependency property on a DependencyObject. (Inherited from DependencyObject)

 

Properties

The LinearGradientBrush class has these properties.

PropertyAccess typeDescription

ColorInterpolationMode

Read/writeGets or sets a ColorInterpolationMode enumeration value that specifies how the gradient's colors are interpolated. (Inherited from GradientBrush)

Dispatcher

Read-onlyGets the CoreDispatcher that this object is associated with. (Inherited from DependencyObject)

EndPoint

Read/writeGets or sets the ending two-dimensional coordinates of the linear gradient.

EndPointProperty

Read-onlyIdentifies the EndPoint dependency property.

GradientStops

Read/writeGets or sets the brush's gradient stops. (Inherited from GradientBrush)

MappingMode

Read/writeGets or sets a BrushMappingMode enumeration value that specifies whether the positioning coordinates of the gradient brush are absolute or relative to the output area. (Inherited from GradientBrush)

Opacity

Read/writeGets or sets the degree of opacity of a Brush. (Inherited from Brush)

RelativeTransform

Read/writeGets or sets the transformation that is applied to the brush using relative coordinates. (Inherited from Brush)

SpreadMethod

Read/writeGets or sets the type of spread method that specifies how to draw a gradient that starts or ends inside the bounds of the object to be painted. (Inherited from GradientBrush)

StartPoint

Read/writeGets or sets the starting two-dimensional coordinates of the linear gradient.

StartPointProperty

Read-onlyIdentifies the StartPoint dependency property.

Transform

Read/writeGets or sets the transformation that is applied to the brush. (Inherited from Brush)

 

Remarks

LinearGradientBrush is a type of Brush that is used for many possible UI properties that use a Brush to fill some or all of an object's visual area in app UI. Examples of some of the most commonly-used properties that use a Brush value include: Control.Background, Control.Foreground, Shape.Fill, Control.BorderBrush, Panel.Background, TextBlock.Foreground. LinearGradientBrush is an alternative to the more commonly used SolidColorBrush type.

The StartPoint and EndPoint properties of LinearGradientBrush describe two points in a relative coordinate space. This creates an orientation for the gradient, and typically this specifies a horizontal gradient, or a vertical gradient. A diagonal gradient can also be used. A LinearGradientBrush typically has two or more GradientStop values for the GradientStops property (an ordered collection). Each GradientStop specifies a Color and an Offset. Offset represents a position between 0 (the StartPoint) and 1 (the EndPoint) along the gradient, and the actual pixel length of the brush and its gradient are adjusted based on the UI where you apply your LinearGradientBrush as a value. For more info on how Offset values are defined and how Offset, StartPoint and EndPoint are related, see Quickstart: Using brushes. It's common to use

You can use the Transparent value for one of the GradientStop colors. Although this doesn't visually apply any changes to UI (it's transparent), that point is detectable for hit-testing purposes. For more info on hit testing, see "Hit testing" section of Responding to mouse interactions.

The GradientStop values of a LinearGradientBrush can be animated as part of transitions or decorative animations. Use one of the dedicated animation types that can animate a Color value. This usually involves having .(GradientStop.Color) be a part of a longer property path for a Storyboard.TargetProperty value. For more info on property targeting and how to animate properties that use Brush values, see Storyboarded animations.

Brushes as XAML resources

Each of the Brush types that can be declared in XAML (SolidColorBrush, LinearGradientBrush, ImageBrush) is intended to be defined as a resource, so that you can reuse that brush as a resource throughout your app. The XAML syntax shown for Brush types is appropriate for defining the brush as a resource. When you declare a brush as a resource, you also need an x:Key attribute that you'll later use to refer to that resource from other UI definitions. For more info on XAML resources and how to use x:Key, see ResourceDictionary and XAML resource references.

The advantage of declaring brushes as resources is that it reduces the number of runtime objects that are needed to construct a UI: the brush is now shared as a common resource that's providing values for multiple parts of the object graph.

If you look at the existing control template definitions for Windows Runtime XAML controls, you'll see that the templates use brush resources extensively (although these are usually SolidColorBrush, not LinearGradientBrush). Many of these resources are system resources, and they use the ThemeResource markup extension for the resource reference rather than StaticResource. For more info on how to use system resource brushes in your own control template XAML, see XAML theme resources reference.

Examples

This example creates a linear gradient with four colors and uses it to paint a Rectangle.


<StackPanel>
  <!-- This rectangle is painted with a vertical linear gradient. -->
  <Rectangle Width="200" Height="100">
    <Rectangle.Fill>
      <LinearGradientBrush StartPoint="0.5,0" EndPoint="0.5,1">
        <GradientStop Color="Yellow" Offset="0.0" />
        <GradientStop Color="Red" Offset="0.25" />
        <GradientStop Color="Blue" Offset="0.75" />
        <GradientStop Color="LimeGreen" Offset="1.0" />
      </LinearGradientBrush>
    </Rectangle.Fill>
  </Rectangle>
</StackPanel>


This illustration shows the resulting gradient. The gradient axis is marked with a dashed line and the gradient stops are marked with circles.

Gradient axis for a vertical gradient

Requirements

Minimum supported client

Windows 8 [Windows Store apps only]

Minimum supported server

Windows Server 2012 [Windows Store apps only]

Minimum supported phone

Windows Phone 8.1 [Windows Runtime apps only]

Namespace

Windows.UI.Xaml.Media
Windows::UI::Xaml::Media [C++]

Metadata

Windows.winmd

See also

GradientBrush
SolidColorBrush
Quickstart: Using brushes
ResourceDictionary and XAML resource references

 

 

Mostrar:
© 2014 Microsoft