UWP倒计时

前台代码：

                    <Grid Width="400" Height="400">
                        <Ellipse Stroke="Gray" StrokeThickness="15"/>
                        <Ellipse x:Name="MyEllipse" Stroke="DeepSkyBlue" StrokeThickness="15"  RenderTransformOrigin="0.5,0.5">
                            <Ellipse.RenderTransform>
                                <RotateTransform Angle="-90"/>
                            </Ellipse.RenderTransform>
                        </Ellipse>
                        <TextBlock x:Name="txt" Foreground="Black" FontSize="50" HorizontalAlignment="Center" VerticalAlignment="Center" ></TextBlock>
                    </Grid>

后台代码：

            int i = 0;
            int TimeCount = 90;//倒计时秒数
            DispatcherTimer timer = new DispatcherTimer() { Interval = new TimeSpan(0, 0, 1) };
            timer.Tick += new EventHandler<object>(async (sender, e) =>
            {
                await Dispatcher.TryRunAsync(CoreDispatcherPriority.Normal, new DispatchedHandler(() =>
                {
                    i += 1;
                    double temp = (385 * Math.PI) * i / TimeCount / 15;
                    MyEllipse.StrokeDashArray = new DoubleCollection() { temp, 1000 };
                    txt.Text = ((TimeCount - i)/60).ToString("00")+":"+((TimeCount - i) % 60).ToString("00");
                    if (i == TimeCount)
                        timer.Stop();
                }));
            });
            timer.Start();

参考文章 ：http://www.cnblogs.com/ms-uap/p/4641419.html