当只有一个图钉时，如何确定 Bing 地图的正确缩放级别？

Question

我在地图上添加了一些图钉，然后“调整大小”或“右缩放”它，以便所有图钉都显示出来，但远边缘的图钉几乎不在边界内，如下所示：

但是，如果只有一个图钉（如下面的爱荷华州的例子，它只有一场内战），而不是尽可能接近零，它会一直缩小到 Skylab，像这样：

这是我用来“调整大小”地图的代码：

private void RightsizeZoomLevelForAllPushpins()
{
    try
    {
        // Set the view so that all pushpins are displayed, with a bit of a margin around them
        // from https://stackoverflow.com/questions/65779504/how-to-set-the-zoom-level-of-bing-map-to-just-wide-enough-to-display-all-pushpin/65781319#65781319
        var map = this.userControl11.myMap;
        var locations = map.Children.OfType<Pushpin>().Select(x => x.Location);
        //Margin
        var w = new Pushpin().Width;
        var h = new Pushpin().Height;
        var margin = new Thickness(w / 2, h, w / 2, 0);

        //Set view
        map.SetView(locations, margin, 0);
        currentZoomLevel = Convert.ToInt32(map.ZoomLevel);
        UncheckAllZoomLevelToolstripMenuItems();
        SetZoomMenuItem();
    }
    catch (Exception ex)
    {
        System.Windows.Forms.MessageBox.Show(ex.Message);
    }
}

如何让一键式地图不仅居中而且尽可能放大？

更新

在对 Count 的两个引用添加括号，并在 else 块中添加一个“if”以便它可以编译后，我仍然收到以下代码的两个错误：

private void RightsizeZoomLevelForAllPushpins()
{
    try
    {
        // Set the view so that all pushpins are displayed, with a bit of a margin around them
        var map = this.userControl11.myMap;
        var locations = map.Children.OfType<Pushpin>().Select(x => x.Location);

        if (locations.Count() == 1)
        {
            map.setView(locations[0], singlePinZoom);                
        }
        else if (locations.Count() > 1) 
        {
            //Margin
            var w = new Pushpin().Width;
            var h = new Pushpin().Height;
            var margin = new Thickness(w / 2, h, w / 2, 0);

            //Set view
            map.SetView(locations, margin, 0);
        }    
        currentZoomLevel = Convert.ToInt32(map.ZoomLevel);
        UncheckAllZoomLevelToolstripMenuItems();
        SetZoomMenuItem();
    }
    catch (Exception ex)
    {
        System.Windows.Forms.MessageBox.Show(ex.Message);
    }
}

他们是：

1>C:\Users\bclay\source\repos\MyMaps\MyMaps\Form1.cs(155,33,155,45): error CS0021: Cannot apply indexing with [] to an expression of type 'IEnumerable<Location>'
1>C:\Users\bclay\source\repos\MyMaps\MyMaps\Form1.cs(155,25,155,32): error CS1061: 'Map' does not contain a definition for 'setView' and no accessible extension method 'setView' accepting a first argument of type 'Map' could be found (are you missing a using directive or an assembly reference?)

顺便说一句，在我编译项目之前，我在 Visual Studio 中看不到任何错误（它在输入错误时停止查找错误）。我不知道为什么...我没有更改任何设置...

更新 2

这是我现在使用的代码，它不只考虑一个图钉，但确实有效（注意“SetView”在这里不会抛出异常）：

private void RightsizeZoomLevelForAllPushpins()
    {
        const int LEFT_TOP_RIGHT_MARGIN_ADDITION = 16;
        const int BOTTOM_MARGIN_ADDITION = 48;
        try
        {
            // Set the view so that all pushpins are displayed, with a bit of a margin around them
            // from https://stackoverflow.com/questions/65779504/how-to-set-the-zoom-level-of-bing-map-to-just-wide-enough-to-display-all-pushpin/65781319#65781319
            var map = this.userControl11.myMap;
            var locations = map.Children.OfType<Pushpin>().Select(x => x.Location);
            //Margin
            var w = new Pushpin().Width;
            var h = new Pushpin().Height;
            var margin = new Thickness((w / 2) + LEFT_TOP_RIGHT_MARGIN_ADDITION, 
                                        h + LEFT_TOP_RIGHT_MARGIN_ADDITION, 
                                        (w / 2) + LEFT_TOP_RIGHT_MARGIN_ADDITION, 
                                        0 + BOTTOM_MARGIN_ADDITION);
            //Set view
            map.SetView(locations, margin, 0);
            currentZoomLevel = Convert.ToInt32(map.ZoomLevel);
            UncheckAllZoomLevelToolstripMenuItems();
            SetZoomMenuItem();
        }
        catch (Exception ex)
        {
            System.Windows.Forms.MessageBox.Show(ex.Message);
        }
    }

Answer 1

单个图钉没有单一的缩放级别，最佳缩放级别取决于您的场景或图钉的含义，以及地图的大小，因为缩放和地图大小都决定了可视区域.例如，如果您的图钉代表一所房子，您可能希望地图放大得比它代表城市时更大。

也就是说，这里是您的代码的修改版本，它将处理单针场景并使用您选择的静态缩放级别：

private double singlePinZoom = 15;

private void RightsizeZoomLevelForAllPushpins()
{
    try
    {
        // Set the view so that all pushpins are displayed, with a bit of a margin around them
        var map = this.userControl11.myMap;
        var locations = map.Children.OfType<Pushpin>().Select(x => x.Location);

        if(locations.Count() > 0) {
            //Margin
            var w = new Pushpin().Width;
            var h = new Pushpin().Height;
            var margin = new Thickness(w / 2, h, w / 2, 0);

            //Set view
            map.SetView(locations, margin, 0);
        } else(locations.Count == 1) {
            map.setView(locations[0], singlePinZoom);
        }   
        
        currentZoomLevel = Convert.ToInt32(map.ZoomLevel);
        UncheckAllZoomLevelToolstripMenuItems();
        SetZoomMenuItem();
    }
    catch (Exception ex)
    {
        System.Windows.Forms.MessageBox.Show(ex.Message);
    }
}

Answer 2

另一篇文章中的答案与这个想法相同，但不幸的是有一些语法错误，并且 if/else 的逻辑是错误的。正如我在 cmets 中提到的，您应该注意以下几点：

1. locations 在你的代码中是IEnumerable<Location> 并且它没有Count 属性，你可以在它上面使用Count() 扩展方法。
2. locations 没有类似数组的索引器，您不能使用 locations[0] 获取第一个元素，而是需要使用 locations.First()。
3. 如果您首先检查Count()>0，then Count()==1 将永远不会命中。所以你需要改变条件，例如先locations.Count() ==1，然后locations.Count() >1。
4. 确保添加useing System.Linq;，以便您可以使用Count() 和First() 方法。

这是您的代码的修改版本：

private void RightsizeZoomLevelForAllPushpins()
{
    try
    {
        var map = this.userControl11.myMap;
        var locations = map.Children.OfType<Pushpin>().Select(x => x.Location);
        if(locations.Count()==1)
        {
            //Your preferred zoom level
            var zoomLevel = 12; 

            //Set view
            map.SetView(locations.First(), zoomLevel );
        }
        else if (locations.Count()>1)
        {
            //Margin
            var w = new Pushpin().Width;
            var h = new Pushpin().Height;
            var margin = new Thickness(w / 2, h, w / 2, 0);

            //Set view
            map.SetView(locations, margin, 0);
        }
        else
        {
            //Not necessary
            System.Windows.Forms.MessageBox.Show("No pushpin.");
        }
        currentZoomLevel = Convert.ToInt32(map.ZoomLevel);
        UncheckAllZoomLevelToolstripMenuItems();
        SetZoomMenuItem();
    }
    catch (Exception ex)
    {
        //Not necessary
        System.Windows.Forms.MessageBox.Show(ex.Message);
    }
}