UWP实现时钟

UWP现在的开发确实很方便，不过资料真的好少啊。。。

前些天看到同学有实实现自定义的时钟，这东东挺简单的，就自己也写个，没成想，遇到个坑，费了好长时间，记下来一下。

效果图：

画个圆，三条线就好。XAML代码如下：

 <Grid Background="{ThemeResource ApplicationPageBackgroundThemeBrush}">
            <Ellipse x:Name="ellipse" Stroke="Black"/>
            <Line x:Name="line_Second" Stroke="Red" StrokeThickness="3"/>
            <Line x:Name="line_Minute" Stroke="Blue" StrokeThickness="2"/>
            <Line x:Name="line_Hour" Stroke="Black" StrokeThickness="1"/>
</Grid>

C#代码：

 public sealed partial class MainPage : Page
    {
        DispatcherTimer timer;//定义定时器
        double ScreenHeight;
        double ScreenWidth;
        double ellipseWidth;
        const double PI = 3.1415926;
        const double lineLength_Second=250;
        const double lineLenght_Minute = 200;
        const double lineLenght_Hour = 150;
        static int second;
        static int minute;
        static int hour;

        public MainPage()
        {
            this.InitializeComponent();
            timer = new DispatcherTimer();
            timer.Interval = new TimeSpan(0, 0, 1);
            timer.Tick += Timer_Tick;//每秒触发这个事件，以刷新指针
            timer.Start();
        }

        private void Timer_Tick(object sender, object e)
        {
            line_Second.X1 = Window.Current.Bounds.Width / 2;
            line_Second.Y1 = Window.Current.Bounds.Height / 2;

            line_Minute.X1= Window.Current.Bounds.Width / 2;
            line_Minute.Y1=Window.Current.Bounds.Height / 2;

            line_Hour.X1= Window.Current.Bounds.Width / 2;
            line_Hour.Y1= Window.Current.Bounds.Height / 2;

            //秒针
            second = DateTime.Now.Second;
            double radius_second =  PI * second / 30;
            line_Second.X2 = lineLength_Second * Math.Sin(radius_second)+ line_Second.X1;
            line_Second.Y2 = line_Second.Y1- lineLength_Second * Math.Cos(radius_second);

            //分针
            minute = DateTime.Now.Minute;
            double radius_minute=  PI * minute / 30;
            line_Minute.X2 = lineLenght_Minute * Math.Sin(radius_minute) + line_Minute.X1;
            line_Minute.Y2 = line_Minute.Y1-lineLenght_Minute * Math.Cos(radius_minute);

            //时针
            hour = DateTime.Now.Hour;
            double radius_hour = hour*PI/6+radius_minute/12;
            line_Hour.X2 = lineLenght_Hour * Math.Sin(radius_hour) + line_Hour.X1;
            line_Hour.Y2 = line_Hour.Y1 - lineLenght_Hour * Math.Cos(radius_hour);
        }

        protected override void OnNavigatedTo(NavigationEventArgs e)
        {
            base.OnNavigatedTo(e);

            //获取窗口实际长宽，以下就是为了适用不同窗体，
            //圆甚至直线的长度也要随窗体变化
            ScreenHeight = Window.Current.Bounds.Height;
            ScreenWidth = Window.Current.Bounds.Width;

            ellipseWidth = ScreenWidth > ScreenHeight ? ScreenHeight - 20 : ScreenWidth - 20;
            ellipse.Height = ellipseWidth;
            ellipse.Width = ellipseWidth;
        }
    }

基础不太好，结果好久才把指针搞对，原因是我对UWP的角度的0°位置不清楚：

窗体左上角为坐标原点，而角度的0°位置如图，调了好久，我还以为写错了，原来是坐标系搞错了，哎