runtime 100.1 中加载天地图/百度/高德/腾讯等底图（二）

       在上一篇runtime 100.1 中加载天地图/百度/高德/腾讯等底图（一）中介绍了加载天地图和高德地图作为底图，这一篇中将介绍如何编写自定义的切片图层。
       编写自定义的切片图层，将使用到ImageTiledLayer类，这里我使用的是可以传回url的类ServiceImageTiledLayer，ImageTiledLayer是根据缩放级别，动态传回ImageTileData数据渲染，加载到地图上，ServiceImageTiledLayer继承自ImageTiledLayer，扩展了一个方法：

Task<Uri> GetTileUriAsync(int level, int row, int column, CancellationToken cancellationToken)

这个方法会根据当前的缩放级别，动态的去指定的url请求图片数据，和WebTiledLayer不同的是，可以继承ServiceImageTiledLayer重写GetTileUriAsync方法，实现不标准url模板的数据请求，比如百度/腾讯等地图数据，下面直接贴代码

    #region 百度地图

    public class BaiduMapLayer : Esri.ArcGISRuntime.Mapping.ServiceImageTiledLayer

    {

        string baidulayerType;

        public BaiduMapLayer(string type = "road")

               : base(CreateTileInfo(), new Envelope(-20037508.3427892, -20037508.3427892, 20037508.3427892, 20037508.3427892, SpatialReferences.WebMercator))

        {

            baidulayerType = type;

        }



        private static Esri.ArcGISRuntime.ArcGISServices.TileInfo CreateTileInfo()

        {

            var levels = new Esri.ArcGISRuntime.ArcGISServices.LevelOfDetail[19];

            double resolution = 20037508.3427892 * 2 / 256;

            double scale = resolution * 96 * 39.37;

            for (int i = 0; i < levels.Length; i++)

            {

                levels[i] = new Esri.ArcGISRuntime.ArcGISServices.LevelOfDetail(i, resolution, scale);

                resolution /= 2;

                scale /= 2;

            }

            return new Esri.ArcGISRuntime.ArcGISServices.TileInfo(96, TileImageFormat.Png, levels, new MapPoint(-20037508.3427892, 20037508.3427892, new SpatialReference(102100)),

                 SpatialReferences.WebMercator, 256, 256);

        }



        private static string subdomains = { "a", "b", "c" };



        protected override Task<Uri> GetTileUriAsync(int level, int row, int col, CancellationToken cancellationToken)

        {



            var zoom = level - 1;

            var offsetX = (int)Math.Pow(2, zoom);

            var offsetY = offsetX - 1;

            var numX = col - offsetX;

            var numY = (-row) + offsetY;

            var num = (col + row) % 8 + 1;

            var url = "";

            switch (this.baidulayerType)

            {

                case "road":

                    url = "http://online" + num + ".map.bdimg.com/tile/?qt=tile&x=" + numX + "&y=" + numY + "&z=" + level + "&styles=pl&udt=20170706";

                    break;

                case "st":

                    url = "http://shangetu3.map.bdimg.com/it/u=x=" + numX + ";y=" + numY + ";z=" + level + ";v=009;type=sate&fm=46&app=webearth2&v=009&udt=20170704";

                    break;

                default:

                    url = "http://online" + num + ".map.bdimg.com/tile/?qt=tile&x=" + numX + "&y=" + numY + "&z=" + level + "&styles=pl&udt=20170706";

                    break;

            }

            return Task.FromResult(new Uri(url, UriKind.Absolute));

        }

    }

    #endregion[/i]

[i]#region 腾讯地图

    public class TencentMapLayer : Esri.ArcGISRuntime.Mapping.ServiceImageTiledLayer

    {

        string tencentlayerType;

        public TencentMapLayer(string layerType = "road")

               : base(CreateTileInfo(), new Envelope(-20037508.3427892, -20037508.3427892, 20037508.3427892, 20037508.3427892, SpatialReferences.WebMercator))

        {

            tencentlayerType = layerType;

        }



        private static Esri.ArcGISRuntime.ArcGISServices.TileInfo CreateTileInfo()

        {

            var levels = new Esri.ArcGISRuntime.ArcGISServices.LevelOfDetail[19];

            double resolution = 20037508.3427892 * 2 / 256;

            double scale = resolution * 96 * 39.37;

            for (int i = 0; i < levels.Length; i++)

            {

                levels[i] = new Esri.ArcGISRuntime.ArcGISServices.LevelOfDetail(i, resolution, scale);

                resolution /= 2;

                scale /= 2;

            }

            return new Esri.ArcGISRuntime.ArcGISServices.TileInfo(96, TileImageFormat.Png, levels, new MapPoint(-20037508.3427892, 20037508.3427892, SpatialReferences.WebMercator),

                 SpatialReferences.WebMercator, 256, 256);

        }







        protected override Task<Uri> GetTileUriAsync(int level, int row, int column, CancellationToken cancellationToken)

        {



            row = (int)Math.Pow(2, level) - 1 - row;

            var url = "";

            switch (this.tencentlayerType)

            {

                case "road":

                    url = $"http://rt0.map.gtimg.com/realtimerender?z={level}&x={column}&y={row}&type=vector&style=0";

                    break;

                case "st":

                    url = $"http://p0.map.gtimg.com/sateTiles/{level}/{Math.Floor((Decimal)column / 16)}/{Math.Floor((Decimal)row / 16)}/{column}_{row}.jpg?version=228";

                    break;

                case "a":

                    url = $"http://rt2.map.gtimg.com/tile?z={level}&x={column}&y={row}&styleid=2&version=232";

                    break;

                default:

                    break;

            }

            return Task.FromResult(new Uri(url, UriKind.Absolute));

        }

    }

    #endregion[/i][/i]

[i][i]    #region openstreet

    public class OpenStreetMapLayer : Esri.ArcGISRuntime.Mapping.ServiceImageTiledLayer

    {

        public OpenStreetMapLayer()

               : base(CreateTileInfo(), new Envelope(-20037508.3427892, -20037508.3427892, 20037508.3427892, 20037508.3427892, SpatialReferences.WebMercator))

        {

        }



        private static Esri.ArcGISRuntime.ArcGISServices.TileInfo CreateTileInfo()

        {

            var levels = new Esri.ArcGISRuntime.ArcGISServices.LevelOfDetail[19];

            double resolution = 20037508.3427892 * 2 / 256;

            double scale = resolution * 96 * 39.37;

            for (int i = 0; i < levels.Length; i++)

            {

                levels[i] = new Esri.ArcGISRuntime.ArcGISServices.LevelOfDetail(i, resolution, scale);

                resolution /= 2;

                scale /= 2;

            }

            return new Esri.ArcGISRuntime.ArcGISServices.TileInfo(96, TileImageFormat.Png, levels, new MapPoint(-20037508.3427892, 20037508.3427892, SpatialReferences.WebMercator),

                 SpatialReferences.WebMercator, 256, 256);

        }



        private static string subdomains = { "a", "b", "c" };



        protected override Task<Uri> GetTileUriAsync(int level, int row, int column, CancellationToken cancellationToken)

        {

            return Task.FromResult(new Uri($"http://{ subdomains[(level + column + row) % subdomains.Length]}.tile.openstreetmap.org/{level}/{column}/{row}.png", UriKind.Absolute));

        }

    }

    #endregion[/i][/i][/i]

[i][i] 如何使用这些类：[/i][/i]
[i][i]var _layer = new BaiduMapLayer();[/i][/i]

[i][i]MyMapView.Map.Basemap.BaseLayers.Add(_layer)[/i][/i]
runtime 100.1 中加载天地图/百度/高德/腾讯等底图（一）:http://zhihu.esrichina.com.cn/article/3246 
runtime 100.1 中加载天地图/百度/高德/腾讯等底图（二）:http://zhihu.esrichina.com.cn/publish/article/3248