#1,155 – A Circular Progress Indicator

Using the earlier custom pie shape control as a base, we can now create a custom control that serves as a circular progress indicator.

Here’s the code for the circular progress control:

    public class CircularProgress : Shape
    {
        static CircularProgress()
        {
            Brush myGreenBrush = new SolidColorBrush(Color.FromArgb(255, 6, 176, 37));
            myGreenBrush.Freeze();

            StrokeProperty.OverrideMetadata(
                typeof(CircularProgress),
                new FrameworkPropertyMetadata(myGreenBrush));
            FillProperty.OverrideMetadata(
                typeof(CircularProgress),
                new FrameworkPropertyMetadata(myGreenBrush));
        }

        // Value (0-100)
        public double Value
        {
            get { return (double)GetValue(ValueProperty); }
            set { SetValue(ValueProperty, value); }
        }

        // DependencyProperty - Value (0 - 100)
        private static FrameworkPropertyMetadata valueMetadata =
                new FrameworkPropertyMetadata(
                    0.0,     // Default value
                    FrameworkPropertyMetadataOptions.AffectsRender,
                    null,    // Property changed callback
                    new CoerceValueCallback(CoerceValue));   // Coerce value callback

        public static readonly DependencyProperty ValueProperty =
            DependencyProperty.Register("Value", typeof(double), typeof(CircularProgress), valueMetadata);

        private static object CoerceValue(DependencyObject depObj, object baseVal)
        {
            double val = (double)baseVal;
            val = Math.Min(val, 99.999);
            val = Math.Max(val, 0.0);
            return val;
        }

        protected override Geometry DefiningGeometry
        {
            get
            {
                double startAngle = 90.0;
                double endAngle = 90.0 - ((Value / 100.0) * 360.0);

                double maxWidth = Math.Max(0.0, RenderSize.Width - StrokeThickness);
                double maxHeight = Math.Max(0.0, RenderSize.Height - StrokeThickness);

                double xStart = maxWidth / 2.0 * Math.Cos(startAngle * Math.PI / 180.0);
                double yStart = maxHeight / 2.0 * Math.Sin(startAngle * Math.PI / 180.0);

                double xEnd = maxWidth / 2.0 * Math.Cos(endAngle * Math.PI / 180.0);
                double yEnd = maxHeight / 2.0 * Math.Sin(endAngle * Math.PI / 180.0);

                StreamGeometry geom = new StreamGeometry();
                using (StreamGeometryContext ctx = geom.Open())
                {
                    ctx.BeginFigure(
                        new Point((RenderSize.Width / 2.0) + xStart,
                                  (RenderSize.Height / 2.0) - yStart),
                        true,   // Filled
                        true);  // Closed
                    ctx.ArcTo(
                        new Point((RenderSize.Width / 2.0) + xEnd,
                                  (RenderSize.Height / 2.0) - yEnd),
                        new Size(maxWidth / 2.0, maxHeight / 2),
                        0.0,     // rotationAngle
                        (startAngle - endAngle) > 180,   // greater than 180 deg?
                        SweepDirection.Clockwise,
                        true,    // isStroked
                        false);
                    ctx.LineTo(new Point((RenderSize.Width / 2.0), (RenderSize.Height / 2.0)), true, false);
                }

                return geom;
            }
        }
    }

Here’s an example of using this control in XAML. The example also includes a traditional progress bar, so that we can compare them.

    <StackPanel>
        <loc:CircularProgress
                 Height="100" Width="100" Margin="5"
                 Value="{Binding PctComplete}"
                 HorizontalAlignment="Center"/>
        <ProgressBar x:Name="prog2" Maximum="100"
                     Value="{Binding PctComplete}"
                     Height="25" Margin="10"/>
        <Button Content="Start Timer" Click="Button_Click"
                HorizontalAlignment="Center"
                Padding="12,7"/>
    </StackPanel>

Finally, here’s the code-behind, including the PctComplete property that we bind to and code that kicks off a timer that updates the property periodically.

    public partial class MainWindow : Window, INotifyPropertyChanged
    {
        public MainWindow()
        {
            this.DataContext = this;
            InitializeComponent();
        }

        public event PropertyChangedEventHandler PropertyChanged = delegate { };

        protected virtual void OnPropertyChanged(string prop)
        {
            PropertyChanged(this, new PropertyChangedEventArgs(prop));
        }

        private double pctComplete = 0.0;
        public double PctComplete
        {
            get { return pctComplete; }
            set
            {
                if (pctComplete != value)
                {
                    pctComplete = value;
                    OnPropertyChanged("PctComplete");
                }
            }
        }

        private void Button_Click(object sender, RoutedEventArgs e)
        {
            PctComplete = 0.0;

            DispatcherTimer timer = new DispatcherTimer();
            timer.Tick += (s, ea) =>
            {
                PctComplete += 1.0;
                if (PctComplete >= 100.0)
                    timer.Stop();
            };
            timer.Interval = new TimeSpan(0, 0, 0, 0, 30);  // 2/sec
            timer.Start();
        }
    }

Here’s the control in action:

1155-001

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About Sean
Software developer in the Twin Cities area, passionate about software development and sailing.

2 Responses to #1,155 – A Circular Progress Indicator

  1. Pingback: Dew Drop – September 10, 2014 (#1852) | Morning Dew

  2. Seema says:

    #1,155 – A Circular Progress Indicator has been a wonderful example. I am a newbie to WPF and I am using this a tutorial.

    I am unable use this part of the code. In fact I fail to understand. Please explain How exactly does this part of the code work? What does tag do in XAML?

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