Como animar um ponto usando quadros-chave

  • Artigo

Este exemplo mostra como usar a PointAnimationUsingKeyFrames classe para animar um Pointarquivo .

Exemplo

O exemplo a seguir move uma elipse ao longo de um caminho triangular. O exemplo usa a classe para animar a PointAnimationUsingKeyFramesCenter propriedade de um EllipseGeometryarquivo . Essa animação usa três quadros-chave da seguinte maneira:

  1. Durante a primeira metade do segundo, usa uma instância da classe para mover a elipse ao longo de LinearPointKeyFrame um caminho a uma taxa constante de sua posição inicial. Quadros-chave lineares como LinearPointKeyFrame criar uma interpolação linear suave entre valores.

  2. Durante o final do próximo meio segundo, usa uma instância da DiscretePointKeyFrame classe para mover repentinamente a elipse ao longo do caminho para a próxima posição. Quadros-chave discretos como DiscretePointKeyFrame criar saltos repentinos entre valores.

  3. Durante os dois segundos finais, usa uma instância da SplinePointKeyFrame classe para mover a elipse de volta à sua posição inicial. Quadros de chave spline como SplinePointKeyFrame criar uma transição variável entre valores de acordo com os valores da KeySpline propriedade. Neste exemplo, a animação começa lentamente e acelera exponencialmente na direção do final do segmento de tempo.

using System;
using System.Windows;
using System.Windows.Controls;
using System.Windows.Shapes;
using System.Windows.Media.Animation;
using System.Windows.Media;

namespace Microsoft.Samples.KeyFrameExamples
{
    /// <summary>
    /// This example shows how to use the PointAnimationUsingKeyFrames class
    /// to animate the position of an object.
    /// </summary>
    public class PointAnimationUsingKeyFramesExample : Page
    {
        public PointAnimationUsingKeyFramesExample()
        {
            Title = "PointAnimationUsingKeyFrames Example";
            Background = Brushes.White;
            Margin = new Thickness(20);

            // Create a NameScope for this page so that
            // Storyboards can be used.
            NameScope.SetNameScope(this, new NameScope());

            // Create an EllipseGeometry.
            EllipseGeometry myAnimatedEllipseGeometry =
                new EllipseGeometry(new Point(200,100), 15, 15);

            // Assign the EllipseGeometry a name so that
            // it can be targeted by a Storyboard.
            this.RegisterName(
                "MyAnimatedEllipseGeometry", myAnimatedEllipseGeometry);

            // Create a Path element to display the geometry.
            Path aPath = new Path();
            aPath.Fill = Brushes.Blue;
            aPath.Data = myAnimatedEllipseGeometry;

            // Create a Canvas to contain the path.
            Canvas containerCanvas = new Canvas();
            containerCanvas.Width = 500;
            containerCanvas.Height = 400;
            containerCanvas.Children.Add(aPath);

            // Create a PointAnimationUsingKeyFrames to
            // animate the EllipseGeometry.
            PointAnimationUsingKeyFrames centerPointAnimation
                = new PointAnimationUsingKeyFrames();
            centerPointAnimation.Duration = TimeSpan.FromSeconds(5);

            // Animate from the starting position to (100,300)
            // over the first half-second using linear
            // interpolation.
            centerPointAnimation.KeyFrames.Add(
                new LinearPointKeyFrame(
                    new Point(100, 300), // Target value (KeyValue)
                    KeyTime.FromTimeSpan(TimeSpan.FromSeconds(0.5))) // KeyTime
                );

            // Animate from (100,300) (the value of the previous key frame)
            // to (400,300) at 1 second using discrete interpolation.
            // Because the interpolation is discrete, the ellipse will appear
            // to "jump" to (400,300) at 1 second.
            centerPointAnimation.KeyFrames.Add(
                new DiscretePointKeyFrame(
                    new Point(400, 300), // Target value (KeyValue)
                    KeyTime.FromTimeSpan(TimeSpan.FromSeconds(1))) // KeyTime
                );

            // Animate from (400,300) (the value of the previous key frame) to (200,100)
            // over two seconds, starting at 1 second (the key time of the
            // last key frame) and ending at 3 seconds.
            centerPointAnimation.KeyFrames.Add(
                new SplinePointKeyFrame(
                    new Point(200, 100), // Target value (KeyValue)
                    KeyTime.FromTimeSpan(TimeSpan.FromSeconds(3)), // KeyTime
                    new KeySpline(0.6, 0.0, 0.9, 0.0) // KeySpline
                    )
                );

            // Set the animation to repeat forever.
            centerPointAnimation.RepeatBehavior = RepeatBehavior.Forever;

            // Set the animation to target the Center property
            // of the object named "MyAnimatedEllipseGeometry".
            Storyboard.SetTargetName(centerPointAnimation, "MyAnimatedEllipseGeometry");
            Storyboard.SetTargetProperty(
                centerPointAnimation, new PropertyPath(EllipseGeometry.CenterProperty));

            // Create a storyboard to apply the animation.
            Storyboard ellipseStoryboard = new Storyboard();
            ellipseStoryboard.Children.Add(centerPointAnimation);

            // Start the storyboard when the Path loads.
            aPath.Loaded += delegate(object sender, RoutedEventArgs e)
            {
                ellipseStoryboard.Begin(this);
            };

            Content = containerCanvas;
        }
    }
}


Imports System.Windows
Imports System.Windows.Controls
Imports System.Windows.Shapes
Imports System.Windows.Media.Animation
Imports System.Windows.Media

Namespace Microsoft.Samples.KeyFrameExamples
    ''' <summary>
    ''' This example shows how to use the PointAnimationUsingKeyFrames class
    ''' to animate the position of an object.
    ''' </summary>
    Public Class PointAnimationUsingKeyFramesExample
        Inherits Page
        Public Sub New()
            Title = "PointAnimationUsingKeyFrames Example"
            Background = Brushes.White
            Margin = New Thickness(20)

            ' Create a NameScope for this page so that
            ' Storyboards can be used.
            NameScope.SetNameScope(Me, New NameScope())

            ' Create an EllipseGeometry.
            Dim myAnimatedEllipseGeometry As New EllipseGeometry(New Point(200,100), 15, 15)

            ' Assign the EllipseGeometry a name so that
            ' it can be targeted by a Storyboard.
            Me.RegisterName("MyAnimatedEllipseGeometry", myAnimatedEllipseGeometry)

            ' Create a Path element to display the geometry.
            Dim aPath As New Path()
            aPath.Fill = Brushes.Blue
            aPath.Data = myAnimatedEllipseGeometry

            ' Create a Canvas to contain the path.
            Dim containerCanvas As New Canvas()
            containerCanvas.Width = 500
            containerCanvas.Height = 400
            containerCanvas.Children.Add(aPath)

            ' Create a PointAnimationUsingKeyFrames to
            ' animate the EllipseGeometry.
            Dim centerPointAnimation As New PointAnimationUsingKeyFrames()
            centerPointAnimation.Duration = TimeSpan.FromSeconds(5)

            ' Animate from the starting position to (100,300)
            ' over the first half-second using linear
            ' interpolation.
            centerPointAnimation.KeyFrames.Add(New LinearPointKeyFrame(New Point(100, 300), KeyTime.FromTimeSpan(TimeSpan.FromSeconds(0.5)))) ' KeyTime -  Target value (KeyValue)

            ' Animate from (100,300) (the value of the previous key frame) 
            ' to (400,300) at 1 second using discrete interpolation.
            ' Because the interpolation is discrete, the ellipse will appear
            ' to "jump" to (400,300) at 1 second.
            centerPointAnimation.KeyFrames.Add(New DiscretePointKeyFrame(New Point(400, 300), KeyTime.FromTimeSpan(TimeSpan.FromSeconds(1)))) ' KeyTime -  Target value (KeyValue)

            ' Animate from (400,300) (the value of the previous key frame) to (200,100)
            ' over two seconds, starting at 1 second (the key time of the
            ' last key frame) and ending at 3 seconds.
            centerPointAnimation.KeyFrames.Add(New SplinePointKeyFrame(New Point(200, 100), KeyTime.FromTimeSpan(TimeSpan.FromSeconds(3)), New KeySpline(0.6, 0.0, 0.9, 0.0))) ' KeySpline -  KeyTime -  Target value (KeyValue)

            ' Set the animation to repeat forever. 
            centerPointAnimation.RepeatBehavior = RepeatBehavior.Forever

            ' Set the animation to target the Center property
            ' of the object named "MyAnimatedEllipseGeometry".
            Storyboard.SetTargetName(centerPointAnimation, "MyAnimatedEllipseGeometry")
            Storyboard.SetTargetProperty(centerPointAnimation, New PropertyPath(EllipseGeometry.CenterProperty))

            ' Create a storyboard to apply the animation.
            Dim ellipseStoryboard As New Storyboard()
            ellipseStoryboard.Children.Add(centerPointAnimation)

            ' Start the storyboard when the Path loads.
            AddHandler aPath.Loaded, Sub(sender As Object, e As RoutedEventArgs) ellipseStoryboard.Begin(Me)

            Content = containerCanvas
        End Sub

    End Class
End Namespace

<Page 
  xmlns="http://schemas.microsoft.com/winfx/2006/xaml/presentation" 
  xmlns:x="http://schemas.microsoft.com/winfx/2006/xaml"
  Background="White" Margin="20">
  <Canvas Width="400" Height="400">
    <Path Fill="Blue">
      <Path.Data>

        <!-- Describes an ellipse. -->
        <EllipseGeometry x:Name="MyAnimatedEllipseGeometry"
          Center="200,100" RadiusX="15" RadiusY="15" />
      </Path.Data>
      <Path.Triggers>
        <EventTrigger RoutedEvent="Path.Loaded">
          <BeginStoryboard>
            <Storyboard>

              <!-- Animating the Center property uses 3 KeyFrames, which animate
                   the ellipse allong a triangular path. -->
              <PointAnimationUsingKeyFrames
                Storyboard.TargetProperty="Center"
                Storyboard.TargetName="MyAnimatedEllipseGeometry"
                Duration="0:0:5" RepeatBehavior="Forever">

                <!-- Over the first half second, Using a LinearPointKeyFrame, the ellipse 
                     moves steadily from its starting position along the first line of the 
                     trianglar path.  -->
                <LinearPointKeyFrame 
                  KeyTime="0:0:0.5"
                  Value="100,300" />

                <!-- Using a DiscretePointKeyFrame, the ellipse suddenly changes position
                     after the first second of the animation. -->
                <DiscretePointKeyFrame 
                  KeyTime="0:0:1"
                  Value="400,300" />

                <!-- Using a SplinePointKeyFrame, the ellipse moves back to its starting
                     position. It moves slowly at first and then speeds up. This key frame 
                     takes 2 seconds to complete. -->
                <SplinePointKeyFrame 
                  KeySpline="0.6,0.0 0.9,0.00" 
                  KeyTime="0:0:3"
                  Value="200,100" />
              </PointAnimationUsingKeyFrames>
            </Storyboard>
          </BeginStoryboard>
        </EventTrigger>
      </Path.Triggers>
    </Path>
  </Canvas>
</Page>

Para ver o exemplo completo, consulte Exemplo de animação de quadro-chave.

Para consistência com outros exemplos de animação, as versões de código deste exemplo usam um Storyboard objeto para aplicar o PointAnimationUsingKeyFrames. No entanto, ao aplicar uma única animação no código, é mais simples usar o BeginAnimation método em vez de usar um Storyboardarquivo . Para obter um exemplo, consulte Animar uma propriedade sem usar um storyboard.

Confira também