【Silverlight】Bing Maps开发应用与技巧二：自定义图钉标注控件和动态ToolPanel

　　在Bing Maps Silverlight Control中以及为我们提供了地图图钉控件Pushpin，我曾经在《使用图钉层（Pushpin layer）及地图图层（MapLayer）》一文中介绍过他的使用方法，本篇主要介绍如何自定义图钉标注控件以及对他的一些扩展，比如实现图钉的动态ToolPanel。

　　关于图钉的UI外观的设计这里就不详细介绍了，通过Blend可以快速的构建UI界面。首先介绍下我的实现思想，通过Path构建图钉标注控件的UI外观，控件整体布局使用Grid布局，分别在Grid容器里设计好图钉UI外观效果和需要动态提示的ToolPanel(使用Border布局设计)，默认将ToolPanel隐藏，在后台代码中通过鼠标事件进行控制其是否出现；另外还布局了一个TextBlock控件，用于出现图钉标注上的内容。下面是定义好的图钉风格的样式：

<Style x:Name="PushpinStyle" TargetType="Controls:PushPinControl">
    <Setter Property="Template">
        <Setter.Value>
            <ControlTemplate TargetType="Controls:PushPinControl">
                <Grid x:Name="grdRoot" Height="Auto" Width="Auto" HorizontalAlignment="Stretch" RenderTransformOrigin="0,0">
                    <Grid.RenderTransform>
                        <TransformGroup>
                            <ScaleTransform x:Name="_ScaleTransform" ScaleX="1" ScaleY="1"/>
                            <SkewTransform/>
                            <RotateTransform/>
                            <TranslateTransform/>
                        </TransformGroup>
                    </Grid.RenderTransform>
                    <Path Stretch="Fill" Opacity="1" RenderTransformOrigin="0.501,0.281" Data="M0,-250L6.09909264359567,
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                          StrokeThickness="2.5" Margin="-28.398,-30.999,0,0" Width="35" Height="30.754" VerticalAlignment="Top" 
                          Fill="#59000000" HorizontalAlignment="Left" d:LayoutOverrides="Width, Height" IsHitTestVisible="False">
                        <Path.RenderTransform>
                            <TransformGroup>
                                <ScaleTransform ScaleX="1" ScaleY="1"/>
                                <SkewTransform AngleX="-57.547" AngleY="0"/>
                                <RotateTransform Angle="0"/>
                                <TranslateTransform X="45.252" Y="0"/>
                            </TransformGroup>
                        </Path.RenderTransform>
                    </Path>
                    <Path Stretch="Fill" Stroke="#FF000000" Opacity="1" RenderTransformOrigin="0.501,0.281" 
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                          StrokeThickness="2.5" HorizontalAlignment="Left" Margin="-18,-63.25,0,0" x:Name="shpPushpin" 
                          Width="35" d:LayoutOverrides="Width" Height="63" 
                          VerticalAlignment="Top" Cursor="Hand">
                        <Path.RenderTransform>
                            <TransformGroup>
                                <ScaleTransform ScaleX="1" ScaleY="1"/>
                                <SkewTransform AngleX="0" AngleY="0"/>
                                <RotateTransform Angle="0"/>
                                <TranslateTransform X="0" Y="0"/>
                            </TransformGroup>
                        </Path.RenderTransform>
                        <Path.Fill>
                            <LinearGradientBrush EndPoint="0.5,1" StartPoint="0.5,0">
                                <GradientStop Color="#FFFFF77F" Offset="0"/>
                                <GradientStop Color="#FFFCF14E" Offset="1"/>
                            </LinearGradientBrush>
                        </Path.Fill>
                    </Path>
                    <TextBlock TextWrapping="Wrap" d:LayoutOverrides="Height, GridBox" RenderTransformOrigin="0.51,0.491" VerticalAlignment="Top" 
                           TextAlignment="Center" Margin="-15.55,-60,0,0" x:Name="txtTitle"
                           Width="30" FontSize="24" Visibility="Visible" FontFamily="Verdana" HorizontalAlignment="Left" IsHitTestVisible="False" >
                            <TextBlock.RenderTransform>
                                <TransformGroup>
                                    <ScaleTransform/>
                                    <SkewTransform AngleX="0" AngleY="0"/>
                                    <RotateTransform Angle="0"/>
                                    <TranslateTransform X="0" Y="0"/>
                                </TransformGroup>
                            </TextBlock.RenderTransform>
                    </TextBlock>
                    <Border x:Name="ToolPanel" VerticalAlignment="Stretch" Background="#A82D2D2D" CornerRadius="8,8,8,8" Visibility="Collapsed" 
                        BorderBrush="#FF626262" BorderThickness="2,2,2,2" ScrollViewer.HorizontalScrollBarVisibility="Visible" 
                        RenderTransformOrigin="0.5,0.5" Grid.Row="0" Width="300" Height="200">
                        <Border.RenderTransform>
                            <TransformGroup>
                                <ScaleTransform/>
                                <SkewTransform/>
                                <RotateTransform/>
                                <TranslateTransform X="20" Y="-75"/>
                            </TransformGroup>
                        </Border.RenderTransform>
                        <StackPanel VerticalAlignment="Top" Margin="5,10, 5, 10">
                            <Grid Height="29" VerticalAlignment="Top">
                                <TextBlock Height="25" Width="346" Text="标题内容" TextWrapping="Wrap" Foreground="#FFF0E7E7" FontSize="16" 
                                    HorizontalAlignment="Left" Margin="12,3,0,1"/>
                            </Grid>
                            <StackPanel VerticalAlignment="Top">
                                <Border x:Name="ContentBorder" Background="#FF000000" CornerRadius="8,8,8,8" VerticalAlignment="Top"
                                        Margin="0,3,0,3" Padding="0,8,0,8" Opacity="0.68" MinHeight="200">
                                    <TextBlock Text="显示内容" Foreground="White" Margin="3" ></TextBlock>
                                </Border>
                            </StackPanel>
                        </StackPanel>
                    </Border>
                </Grid>
            </ControlTemplate>
        </Setter.Value>
    </Setter>
</Style>

　　接下来要做的就是实现图标注控件的定义以及动态控制ToolPanel控件的显示与否了，主要思路就是通过引用上面定义的样式，以模板的方式从样式里获取到相应的控件元素进行动态控制，详细见如下代码：

/// <summary>
/// 自定义图钉控件
/// </summary>
public class PushPinControl : ContentControl
{
    private string Text;

    public PushPinControl(String text)
    {
        //设置图钉标注控件的标注内容
        this.Text = text == "" ? "M" : text;
        DefaultStyleKey = typeof(PushPinControl);
        //为当前对象引用样式，从全局资源里读取
        this.Style = Application.Current.Resources["PushpinStyle"] as Style;
    }

    public override void OnApplyTemplate()
    {
        base.OnApplyTemplate();

        //从样式模板中获取TextBlock控件
        var textBlock = GetTemplateChild("txtTitle") as TextBlock;
        textBlock.Text = this.Text;
        //从样式模板中获取ToolPanel(既Border布局实现的，详细见样式的定义)控件
        var ToolPanelBorder = GetTemplateChild("ToolPanel") as Border;
        //通过事件动态控制ToolPanel的显示和隐藏
        this.MouseEnter += (mes, meo) => { ToolPanelBorder.Visibility = Visibility.Visible; };
        this.MouseLeave += (mls, mlo) => { ToolPanelBorder.Visibility = Visibility.Collapsed; };
    }
}

 　　　　　　　

　　到这里就成功的完成了图钉标注控件的自定义了，接下来看看如何使用这个自定义的图钉标注控件，详见如下代码块：

private void AddPushPin()
{
    //添加Bing Maps Silverlight Control自带的图钉
    //var pushpin = new Pushpin();
    //pushpin.Location = new Location(29.5076372217973, 106.489384971208);
    //添加自定义的图钉
    var pushpin = new PushPinControl("D");
    MapLayer.AddChild(pushpin, new Location(29.5076372217973, 106.489384971208));
}

　　　　　　　

　　或许会有人问道，如何动态的实现ToolPanel里显示的内容？要实现这个功能也是非常简单的，首先我们来分析下上面定义的样式里对ToolPanel部分的定义：

<Border x:Name="ToolPanel" VerticalAlignment="Stretch" Background="#A82D2D2D" CornerRadius="8,8,8,8" Visibility="Collapsed" 
    BorderBrush="#FF626262" BorderThickness="2,2,2,2" ScrollViewer.HorizontalScrollBarVisibility="Visible" 
    RenderTransformOrigin="0.5,0.5" Grid.Row="0" Width="300" Height="200">
    <Border.RenderTransform>
        <TransformGroup>
            <ScaleTransform/>
            <SkewTransform/>
            <RotateTransform/>
            <TranslateTransform X="20" Y="-75"/>
        </TransformGroup>
    </Border.RenderTransform>
    <StackPanel VerticalAlignment="Top" Margin="5,10, 5, 10">
        <Grid Height="29" VerticalAlignment="Top">
            <TextBlock Height="25" Width="346" Text="标题内容" TextWrapping="Wrap" Foreground="#FFF0E7E7" FontSize="16" 
                HorizontalAlignment="Left" Margin="12,3,0,1"/>
        </Grid>
        <StackPanel VerticalAlignment="Top">
            <Border x:Name="ContentBorder" Background="#FF000000" CornerRadius="8,8,8,8" VerticalAlignment="Top"
                    Margin="0,3,0,3" Padding="0,8,0,8" Opacity="0.68" MinHeight="200">
                <TextBlock Text="显示内容" Foreground="White" Margin="3" ></TextBlock>
            </Border>
        </StackPanel>
    </StackPanel>
</Border>

　　使用了Border进行圆角布局，在其内部通过StackPanel垂直布局实现了ToolPanel的的标题和内容两大部分，内容部分并通过Border进行设计，取名为ContentBorder，这是为了实现动态呈现显示内容而设计，整体Border通过TranslateTransform进行一个偏移的处理，也就是让ToolPanel始终显示在图钉标注的右边相应的位置，详细见本文前面提供的截图。

　　从上面的实现知道ToolPanel是在鼠标的MouseEnter事件执行的时候才会显示的，当鼠标离开就会将其可见性设置为隐藏。了解了这个原理后就可以想到，是否可以从MouseEnter事件中通过某种方法去处理？事件是个非常强大的技术点，这里我们就可以通过事件，将显示内容的Border容器派发处理，通过事件的监听来动态更新其显示内容。首先需要扩展一个事件类：

public delegate void PushpinContentChangedHandler(object sender,PushpinContentChangedEvantAgrs e);

public class PushpinContentChangedEvantAgrs : EventArgs
{
    public Border ContentBorder { get; set; }

    public PushpinContentChangedEvantAgrs() { }

    public PushpinContentChangedEvantAgrs(Border ContentBorder)
    {
        this.ContentBorder = ContentBorder;
    }
}

     接下来为自定义的图钉标注类定义一个事件，事件类型就为上面所定义好的委托类型，传递的事件为PushpinContentChangedEventArgs.

/// <summary>
/// 自定义图钉控件
/// </summary>
public class PushPinControl : ContentControl
{
    public event PushpinContentChangedHandler ContentChangedEvent;

 

    现在需要做的就是在当前对象的MouseEnter事件中去触发这个事件，将样式里所定义好的用于显示内容的Border对象获取出来，通过事件参数传递派发出去，让事件监听段可以通过该事件获取事件参数进行ToolPanel内容的呈现更新。所有我们需要改写PushPinControl的OnApplyTemplate方法：

public override void OnApplyTemplate()
{
    base.OnApplyTemplate();

    //从样式模板中获取TextBlock控件
    var textBlock = GetTemplateChild("txtTitle") as TextBlock;
    textBlock.Text = this.Text;
    //从样式模板中获取ToolPanel(既Border布局实现的，详细见样式的定义)控件
    var ToolPanelBorder = GetTemplateChild("ToolPanel") as Border;
    //获取内容Border对象，通过事件将该对象派发出去，在使用段可以通过监听这个事件而获取到内容Border
    var ContentBorder = GetTemplateChild("ContentBorder") as Border;
    //通过事件动态控制ToolPanel的显示和隐藏
    this.MouseEnter += (mes, meo) => 
    { 
        ToolPanelBorder.Visibility = Visibility.Visible;  
        if (ContentChangedEvent != null)
        {
            ContentChangedEvent(this, new PushpinContentChangedEvantAgrs(ContentBorder));
        }
    };
    this.MouseLeave += (mls, mlo) => { ToolPanelBorder.Visibility = Visibility.Collapsed; };
}

 　　通过ContentChangedEvent事件的监听动态的去改变ToolPanel里的显示内容就可以达到我们的目的了，比如我们动态的将ToolPanel里的显示内容更改为一张图片，上面使用自定义图钉标注的代码将变成下面这样的。

private void AddPushPin()
{
    //添加Bing Maps Silverlight Control自带的图钉
    //var pushpin = new Pushpin();
    //pushpin.Location = new Location(29.5076372217973, 106.489384971208);
    //添加自定义的图钉
    var pushpin = new PushPinControl("D");
    pushpin.ContentChangedEvent += (sender, o) =>
        {
            //构造Image对象 用于显示在ToolPanel中
            var image = new Image { Width = 100, Height = 100, Margin = new Thickness(8) };
            image.Source = new BitmapImage(new Uri("Resources/Smbecker.png", UriKind.RelativeOrAbsolute));
            Border border = o.ContentBorder;

            border.Child = image;
        };
    MapLayer.AddChild(pushpin, new Location(29.5076372217973, 106.489384971208));
}

　　　　　　　　 

　　之前有网友问到如何实现可拖拽的图钉标注控件，鉴于篇幅的原因这里就不做介绍，不清楚的朋友可以留言讨论。本篇就介绍到这里，欢迎大家前来交流、讨论、拍砖。

　　更多学习资料：

　　MSDN:http://msdn.microsoft.com/en-us/library/ee681890.aspx

　　官方：http://www.microsoft.com/maps

　　中国Bing Maps:http://cn.bing.com/ditu/

　　官方SDK：http://www.microsoft.com/maps/isdk/silverlight/

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  作      者：Beniao                                 微软Bing Maps开发QQ群：75662563

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