从 CSV 文件中提取数据（融合表和 kml 解决方法）

在使用 C# 的 Android 版 Xamarin 谷歌地图中，​​您可以基于此创建多边形tutorial:

    public void OnMapReady(GoogleMap googleMap)
    {
        mMap = googleMap;
        PolylineOptions geometry = new PolylineOptions()
        .Add(new LatLng(37.35, -37.0123))
        .Add(new LatLng(37.35, -37.0123))
        .Add(new LatLng(37.35, -37.0123));


        Polyline polyline = mMap.AddPolyline(geometry);

    }

不过，我已经从谷歌地图的 Fusion Table Layer 下载了一个 CSV 文件，因为我认为这可能是处理多边形/折线数据的最简单的选项。输出如下所示：

    description,name,label,geometry
    ,Highland,61,"<Polygon><outerBoundaryIs><LinearRing><coordinates>-5.657018,57.3352 -5.656396,57.334463 -5.655076,57.334556 -5.653439,57.334477 -5.652366,57.334724 -5.650064,57.334477 -5.648096,57.335082 -5.646846,57.335388 -5.644733,57.335539 -5.643309,57.335428 -5.641981,57.335448 -5.640451,57.33578 -5.633217,57.339118 -5.627278,57.338921 -5.617161,57.337649 -5.607948,57.341015 -5.595812,57.343583 -5.586043,57.345373 -5.583581,57.350648 -5.576851,57.353609 -5.570088,57.354017 -5.560732,57.354102 -5.555254,57.354033 -5.549713,57.353146 -5.547766,57.352275 -5.538932,57.352255 -5.525891,57.356217 -5.514888,57.361865 -5.504272,57.366027 -5.494515,57.374515 -5.469829,57.383765 -5.458661,57.389781 -5.453695,57.395033 -5.454057,57.402943 -5.449189,57.40731 -5.440583,57.411447 -5.436133,57.414616 -5.438312,57.415474 -5.438628,57.417955 -5.440956,57.417909 -5.444013,57.414976 -5.450778,57.421362 -5.455035,57.422333 -5.462081,57.420719 -5.468775,57.416975 -5.475205,57.41135 -5.475976,57.409117 -5.47705,57.407092 -5.478101,57.406056 -5.478901,57.40536 -5.479489,57.404534 -5.480051,57.403782 -5.481036,57.403107 -5.484538,57.402102 -5.485647,57.401856 -5.487358,57.401287 -5.488709,57.400962 -5.490175,57.400616 -5.491116,57.400176 -5.493832,57.399318 -5.495279,57.399134 -5.496726,57.39771 -5.498724,57.396836 -5.49974,57.396314 -5.501317,57.39627 -5.502869,57.395426</coordinates></LinearRing></innerBoundaryIs></Polygon>"
    ,Strathclyde,63,"<Polygon><outerBoundaryIs><LinearRing><coordinates>-5.603129,56.313564 -5.603163,56.312536 -5.603643,56.311794 -5.601467,56.311875 -5.601038,56.312481 -5.600697,56.313489 -5.60071,56.31535 -5.60159,56.316107 -5.600729,56.316598 -5.598625,56.316058 -5.596203,56.317477 -5.597024,56.318119 -5.596095,56.318739 -5.595432,56.320116 -5.589343,56.322469 -5.584888,56.325178 -5.582907,56.327169 -5.581414,56.327472 -5.581435,56.326663 -5.582355,56.325602 -5.581515,56.323891 -5.576993,56.331062 -5.57886,56.331475 -5.57676,56.334449 -5.572748,56.335689 -5.569012,56.338143 -5.564802,56.342113 -5.555237,56.346668 -5.551214,56.347448 -5.547651,56.346391 -5.54444,56.344945 -5.541247,56.345945 -5.539099,56.349674 -5.533874,56.34763 -5.525195,56.342888 -5.523518,56.345066 -5.52345,56.346605 -5.526417,56.354361 -5.535455,56.353681 -5.537463,56.35508 -5.536035,56.356271 -5.538923,56.357205 -5.53891,56.359336 -5.539952,56.361491 -5.538102,56.36372 -5.535934,56.36567 -5.53392,56.367705 -5.531369,56.369729 -5.529853,56.371022 -5.532371,56.371274 -5.534177,56.371708 -5.532846,56.373256 -5.529845,56.37496 -5.527675,56.375327 -5.528531,56.375995 -5.526732,56.376343 -5.525442,56.377809 -5.524739,56.379843 -5.526069,56.380561</coordinates></LinearRing></innerBoundaryIs></Polygon>"

我将 KML 文件上传到Google Maps Fusion Table Layer，然后它创建了map。然后我就去了File>Download>CSV它给了我上面的例子。

我已将此 csv 文件添加到我的 xamarin android google 地图应用程序的资产文件夹中，我的问题是因为LatLng采用两个双精度数作为输入，有没有办法可以将 csv 文件中的上述数据输入到此方法中，如果可以，如何输入？

不知道如何做read the above csv然后提取<coordinates>然后将这些坐标添加为新坐标LatLng在上面的示例代码中？

如果您注意到坐标被分为纬度和经度，然后是下一个latlng由一个分隔space -5.657018,57.3352 -5.656396,57.334463.

Sudo 代码（这可能需要也可能不需要 xamarin 或 android 经验，可能只需要 C#/Linq）:

Read CSV var sr = new StreamReader(Read csv from Asset folder);
Remove description,name,label,geometry
Foreach line in CSV
  Extract Item that contains double qoutes
     Foreach Item Remove Qoutes and <Polygon><outerBoundaryIs><LinearRing><coordinates> from start and end
         Foreach item seperated by a space Extract coordinates
       (This will now leave a long list of 37.35,-37.0123 coordinates for each line)
        Place in something like this maybe?:

    public class Row
    {
        public double Lat { get; set; }
        public double Lng { get; set; }

        public Row(string str)
        {
            string[] separator = { "," };
            var arr = str.Split(separator, StringSplitOptions.None);
            Lat = Convert.ToDouble(arr[0]);
            Lng = Convert.ToDouble(arr[1]);
        }
    }


    private void OnMapReady()
    var rows = new List<Row>();

      Foreach name/new line
         PolylineOptions geometry = new PolylineOptions()
           ForEach (item in rows) //not sure how polyline options will take a foreach
            .Add(New LatLng(item.Lat, item.Lng))
         Polyline polyline = mMap.AddPolyline(geometry);

由于无法将 Xamarin Android 中的 Fusion Table Layers 与 Google Maps API v2 一起使用，这可能为那些需要将地图拆分为区域的人提供快速且更简单的解决方法。

如果我理解正确的话，问题是如何解析上面的 CSV 文件。

每行（除了第一行带标题的行）都可以用以下类表示：

class MapEntry
{
    public string Description { get; set; }
    public string Name { get; set; }
    public string Label { get; set; }
    public IEnumerable<LatLng> InnerCoordinates { get; set; }
    public IEnumerable<LatLng> OuterCoordinates { get; set; }
}

请注意Inner and Outer坐标。它们在 XML 中表示为outerBoundaryIs（必填）和innerBoundaryIs（可选）元素。

附注：Highland您帖子中的行不正确 - 您似乎修剪了该行的一部分，导致 XML 不正确（<outerBoundaryIs>...</innerBoundaryIs>).

这是进行解析的代码：

static IEnumerable<MapEntry> ParseMap(string csvFile)
{
    return from line in File.ReadLines(csvFile).Skip(1)
           let tokens = line.Split(new[] { ',' }, 4)
           let xmlToken = tokens[3]
           let xmlText = xmlToken.Substring(1, xmlToken.Length - 2)
           let xmlRoot = XElement.Parse(xmlText)
           select new MapEntry
           {
               Description = tokens[0],
               Name = tokens[1],
               Label = tokens[2],
               InnerCoordinates = GetCoordinates(xmlRoot.Element("innerBoundaryIs")),
               OuterCoordinates = GetCoordinates(xmlRoot.Element("outerBoundaryIs")),
           };
}

static IEnumerable<LatLng> GetCoordinates(XElement node)
{
    if (node == null) return Enumerable.Empty<LatLng>();
    var element = node.Element("LinearRing").Element("coordinates");
    return from token in element.Value.Split(' ')
           let values = token.Split(',')
           select new LatLng(XmlConvert.ToDouble(values[0]), XmlConvert.ToDouble(values[1]));
}

我认为代码是不言自明的。唯一需要提及的细节是：

let tokens = line.Split(new[] { ',' }, 4)

这里我们使用string.Split overload这使我们能够指定要返回的子字符串的最大数量，从而避免处理 XML 令牌内的逗号的陷阱。

and:

let xmlText = xmlToken.Substring(1, xmlToken.Length - 2)

它从 XML 标记中删除引号。

最后，为您的案例提供一个示例用法：

foreach (var entry in ParseMap(csv_file_full_path))
{
    PolylineOptions geometry = new PolylineOptions()
    foreach (var item in entry.OuterCoordinates)
        geometry.Add(item)
    Polyline polyline = mMap.AddPolyline(geometry);
}

UPDATE:为了让 Xamarin 满意（如评论中所述），请替换File.ReadLines调用以下助手：

static IEnumerable<string> ReadLines(string path)
{
    var sr = new StreamReader(Assets.Open(path));
    try
    {
        string line;
        while ((line = sr.ReadLine()) != null)
            yield return line; 
    }
    finally { sr.Dispose(); }
}