Cómo: Cambiar la velocidad de un reloj sin cambiar la velocidad de su escala de tiempo

Actualización: noviembre 2007

La propiedad SpeedRatio de un objeto ClockController permite cambiar la velocidad de un objeto Clock sin modificar la propiedad SpeedRatio de la escala de tiempo (Timeline) del reloj. En el ejemplo siguiente, se utiliza un controlador ClockController para modificar interactivamente la propiedad SpeedRatio de un reloj. El evento CurrentGlobalSpeedInvalidated y la propiedad CurrentGlobalSpeed del reloj se utilizan para mostrar la velocidad global actual del reloj cada vez que se cambia su SpeedRatio interactiva.

Ejemplo

/*
  This example shows how to interactively control 
  the speed of a clock
*/
using System;
using System.Windows;
using System.Windows.Controls;
using System.Windows.Media;
using System.Windows.Shapes;
using System.Windows.Media.Animation;

namespace Microsoft.Samples.Animation.TimingBehaviors
{
    public class ClockControllerSpeedRatioExample : Page
    {

        private AnimationClock myControllableClock;
        private Button speedRatioButton;
        private TextBox speedRatioSettingTextBox;
        private double doubleParseResult = 1;
        private TextBlock currentGlobalSpeedTextBlock;

        public ClockControllerSpeedRatioExample()
        {
            StackPanel mainPanel = new StackPanel();

            // Create a rectangle to animate.
            Rectangle animatedRectangle = new Rectangle();
            animatedRectangle.Width = 100;
            animatedRectangle.Height = 100;
            animatedRectangle.Fill = Brushes.Orange;
            mainPanel.Children.Add(animatedRectangle);
            // Create a DoubleAnimation to
            // animate its width.
            DoubleAnimation widthAnimation = 
                new DoubleAnimation(
                    100,
                    500, 
                    new Duration(TimeSpan.FromSeconds(5)));
            //widthAnimation.RepeatBehavior = RepeatBehavior.Forever;
            widthAnimation.AutoReverse = true;
            widthAnimation.SpeedRatio = 0.5;

            // Create a clock from the animation.
            myControllableClock = widthAnimation.CreateClock();

            // Apply the clock to the rectangle's Width property.
            animatedRectangle.ApplyAnimationClock(
                Rectangle.WidthProperty, myControllableClock);    

            //
            // Create some controls the enable the user to
            // interactively control the SpeedRatio of the clock. 
            //            
            StackPanel speedRatioDetailsPanel = new StackPanel();
            speedRatioDetailsPanel.Margin = new Thickness(0,20,0,20);
            speedRatioDetailsPanel.Orientation = Orientation.Horizontal;
            Label speedRatioLabel = new Label();
            speedRatioLabel.Content = "Speed Ratio:";
            speedRatioDetailsPanel.Children.Add(speedRatioLabel);

            // Create a text box so that the user can
            // specify the amount by which to seek.
            speedRatioSettingTextBox = new TextBox();
            speedRatioSettingTextBox.Text = 
                myControllableClock.Controller.SpeedRatio.ToString();
            speedRatioSettingTextBox.VerticalAlignment = VerticalAlignment.Top;
            speedRatioSettingTextBox.TextChanged += 
                new TextChangedEventHandler(seekAmountTextBox_TextChanged);
            speedRatioDetailsPanel.Children.Add(speedRatioSettingTextBox);          

            // Create a button to apply SpeedRatio changes.
            speedRatioButton = new Button();
            speedRatioButton.Content = "Apply Speed Ratio";
            speedRatioButton.Click += new RoutedEventHandler(speedRatioButton_Clicked);  
            speedRatioDetailsPanel.Children.Add(speedRatioButton);

            mainPanel.Children.Add(speedRatioDetailsPanel);

            // Display the clock's global speed information.
            Label myLabel = new Label();
            myLabel.Content = "CurrentGlobalSpeed ";
            mainPanel.Children.Add(myLabel);
            currentGlobalSpeedTextBlock = new TextBlock();
            currentGlobalSpeedTextBlock.Text = 
                myControllableClock.CurrentGlobalSpeed.ToString();
            mainPanel.Children.Add(currentGlobalSpeedTextBlock);

            // List for speed changes.
            myControllableClock.CurrentGlobalSpeedInvalidated += 
                new EventHandler(myControllableClock_currentGlobalSpeedInvalidated);

            this.Content = mainPanel;
        }


        // Updates the clock's SpeedRatio.
        private void speedRatioButton_Clicked(object sender, RoutedEventArgs e)
        {

            // This statement triggers a CurrentGlobalSpeedInvalidated
            // event.
            myControllableClock.Controller.SpeedRatio = doubleParseResult; 

        }

        // Displays the current global speed.
        private void myControllableClock_currentGlobalSpeedInvalidated(object sender, EventArgs e)
        {

            currentGlobalSpeedTextBlock.Text = 
                myControllableClock.CurrentGlobalSpeed.ToString()
                + " Event triggered at: " 
                + DateTime.Now.ToString();   

        }        

        // Verifies that speedRatioSettingTextBox has valid text content.
        // If it doesn't, the speedRatioButton is disabled.
        private void seekAmountTextBox_TextChanged(object sender, TextChangedEventArgs e)
        {

            TextBox theTextBox = (TextBox)e.Source;
            if (theTextBox.Text == null || theTextBox.Text.Length < 1
                || Double.TryParse(theTextBox.Text, 
                    System.Globalization.NumberStyles.Any, 
                    null, out doubleParseResult) == false)
                speedRatioButton.IsEnabled = false;
            else 
                speedRatioButton.IsEnabled = true;

        }

    }
}