Procedura: modificare la velocità di un orologio senza cambiare la velocità della relativa sequenza temporale

Aggiornamento: novembre 2007

La proprietà SpeedRatio di un oggetto ClockController consente di modificare la velocità di un oggetto Clock senza alterare la proprietà SpeedRatio dell'oggetto Timeline dell'orologio. Nell'esempio seguente viene utilizzato un oggetto ClockController per modificare in modo interattivo SpeedRatio di un orologio. L'evento CurrentGlobalSpeedInvalidated e la proprietà CurrentGlobalSpeed dell'orologio sono utilizzati per visualizzare la velocità globale corrente dell'orologio tutte le volte che l'oggetto SpeedRatio interattivo viene modificato.

Esempio

/*
  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;

        }

    }
}