wp7屏幕地图

实际大小超出屏幕范围时，显示屏幕对应的位置，如图

具体代码如下：

<Grid x:Name="LayoutRoot">
        <Border BorderBrush="AliceBlue" HorizontalAlignment="Right" BorderThickness="5" VerticalAlignment="Top"  Height="330" Width="250" >
            <Canvas>
                <Image Canvas.Left="0" Canvas.Top="0" Name="img" Height="320" Width="240" Stretch="Fill"/>
                <Rectangle Name="rcLocation" Canvas.Left="0" Canvas.Top="0" Canvas.ZIndex="1" Stroke="Red"  Height="10" Width="180"/>
            </Canvas>
        </Border>
        <ScrollViewer  Name="sc" HorizontalScrollBarVisibility="Hidden" VerticalScrollBarVisibility="Hidden">
            <StackPanel Width="600" Name="content">
                <TextBlock Text="windows phone："/>
                <TextBox Width="200" HorizontalAlignment="Left"/>
                <TextBlock Text="windows phone："/>
                <TextBox Width="200" HorizontalAlignment="Left"/>
                <TextBlock Text="windows phone："/>
                <TextBox Width="200" HorizontalAlignment="Left"/>
                <TextBlock Text="windows phone："/>
                <TextBox/>
                <TextBlock Text="windows phone："/>
                <TextBox/>
                <TextBlock Text="windows phone："/>
                <TextBox/>
                <TextBlock Text="windows phone："/>
                <TextBox/>
                <TextBlock Text="windows phone："/>
                <TextBox/>
                <TextBlock Text="windows phone："/>
                <TextBox/>
                <TextBlock Text="windows phone："/>
                <TextBox/>
                <TextBlock Text="windows phone："/>
                <TextBox/>
                <TextBlock Text="windows phone："/>
                <TextBox/>
                <TextBlock Text="windows phone："/>
                <TextBox/>
            </StackPanel>
        </ScrollViewer>
    </Grid>

public partial class MainPage : PhoneApplicationPage
    {
        // Constructor
        public MainPage()
        {
            InitializeComponent();
            this.Loaded += new RoutedEventHandler(MainPage_Loaded);
        }

        ScrollBar hScrollBar, vScrollBar;

        void MainPage_Loaded(object sender, RoutedEventArgs e)
        {
            CompositionTarget.Rendering += new EventHandler(CompositionTarget_Rendering);

            hScrollBar = GetScrollBar(sc, true);
            vScrollBar = GetScrollBar(sc, false);
            hScrollBar.ValueChanged += new RoutedPropertyChangedEventHandler<double>(hScrollBar_ValueChanged);
            vScrollBar.ValueChanged += new RoutedPropertyChangedEventHandler<double>(vScrollBar_ValueChanged);

            rcLocation.Height = content.ActualHeight >= 800 ? 800 / content.ActualHeight * 320 : 320;
            rcLocation.Width = content.ActualWidth >= 480 ? 480 / content.ActualWidth * 240 : 240;
        }

        /// <summary>
        /// 垂直滚动条
        /// </summary>
        void vScrollBar_ValueChanged(object sender, RoutedPropertyChangedEventArgs<double> e)
        {
            this.rcLocation.SetValue(Canvas.TopProperty, e.NewValue / content.ActualHeight * 320);
        }

        /// <summary>
        /// 水平滚动条
        /// </summary>
        void hScrollBar_ValueChanged(object sender, RoutedPropertyChangedEventArgs<double> e)
        {
            this.rcLocation.SetValue(Canvas.LeftProperty, e.NewValue / content.ActualWidth * 320);
        }


        void CompositionTarget_Rendering(object sender, EventArgs e)
        {
            WriteableBitmap bit = new WriteableBitmap(content, null);
            img.Source = bit;
        }

        private ScrollBar GetScrollBar(ScrollViewer viewer, bool isHor)
        {
            var a = VisualTreeHelper.GetChild(viewer, 0);
            var b = VisualTreeHelper.GetChild(a, 0);
            var c = VisualTreeHelper.GetChild(b, 0);

            if (isHor)
                return VisualTreeHelper.GetChild(b, 2) as ScrollBar;//水平
            else
                return VisualTreeHelper.GetChild(b, 1) as ScrollBar;//垂直           
        }
    }