4.02WorldWindAndroid加载天地图在线非正切片地图

WorldWindAndroid对于TileImage的加载默认是按照等经纬差的正切片加载的，经圈范围-180--180，纬圈范围-90--90，所以，经纬方向上的切片规格为2X1！

为了能够加载经纬差之比为2：1的切片服务，需要将加载正切片的方式进行一定的处理，才能正确加载本服务！

1、第一级切片的范围重设置

Sector sector1 = new Sector(sector.minLatitude(), sector.minLongitude() * 2 + 180, sector.deltaLatitude(), sector.deltaLongitude() * 2);

纬度起点不变，但经度上要偏移原来的2倍，同时纬度差不变，经度差要变为原来的2倍，对应经纬差为2：1的切片。

2、顶级切片之下做子切片

此时不能像顶级切片一样设置，因为子切片是在上一级切片的基础上得到的，将一张父切片等分为四分，此时获得的子切片的起点经纬度是正确的，不能再将经度偏移2倍，而只需要将经差设为2倍即可。

Tile类

 public Tile[] subdivide(TileFactory tileFactory) {
        if (tileFactory == null) {
            throw new IllegalArgumentException(
                Logger.logMessage(Logger.ERROR, "Tile", "subdivide", "missingTileFactory"));
        }

        Level childLevel = this.level.nextLevel();
        if (childLevel == null) {
            return null;
        }

        Tile[] children = new Tile[4];
        double latMin = this.sector.minLatitude();
        double lonMin = this.sector.minLongitude();
        double latMid = this.sector.centroidLatitude();
        double lonMid = this.sector.centroidLongitude();
        double childDelta = this.level.tileDelta * 0.5;

        int childRow = 2 * this.row;
        int childCol = 2 * this.column;
        Sector childSector = new Sector(latMin, lonMin, childDelta, childDelta);
        children[0] = tileFactory.createTile(childSector, childLevel, childRow, childCol); // Southwest

        childRow = 2 * this.row;
        childCol = 2 * this.column + 1;
        childSector = new Sector(latMin, lonMid, childDelta, childDelta);
        children[1] = tileFactory.createTile(childSector, childLevel, childRow, childCol); // Southeast

        childRow = 2 * this.row + 1;
        childCol = 2 * this.column;
        childSector = new Sector(latMid, lonMin, childDelta, childDelta);
        children[2] = tileFactory.createTile(childSector, childLevel, childRow, childCol); // Northwest

        childRow = 2 * this.row + 1;
        childCol = 2 * this.column + 1;
        childSector = new Sector(latMid, lonMid, childDelta, childDelta);
        children[3] = tileFactory.createTile(childSector, childLevel, childRow, childCol); // Northeast

        return children;
    }

 if(level.levelNumber>0){
          sector1 = new Sector(sector.minLatitude(), sector.minLongitude() , sector.deltaLatitude(), sector.deltaLongitude() * 2);
          tile = new ImageTile(sector1, level, row, column);
        }

3、切片服务的起点在左上角（-180，90），而WorldWindAndroid中为左下角（-180，-90），所以，行数上略作变换

int row1 = (int) Math.pow(2, (level.levelNumber + 2)) - 1 - row;

最后，得到完整的加载类TiandituVecLayer 如下：

import gov.nasa.worldwind.WorldWind;
import gov.nasa.worldwind.geom.Sector;
import gov.nasa.worldwind.render.ImageOptions;
import gov.nasa.worldwind.render.ImageSource;
import gov.nasa.worldwind.render.ImageTile;
import gov.nasa.worldwind.shape.TiledSurfaceImage;
import gov.nasa.worldwind.util.Level;
import gov.nasa.worldwind.util.LevelSet;
import gov.nasa.worldwind.util.LevelSetConfig;
import gov.nasa.worldwind.util.Logger;
import gov.nasa.worldwind.util.Tile;
import gov.nasa.worldwind.util.TileFactory;

/**
 * Created by Lenovo on 2018/4/1.
 */

public class TiandituVecLayer extends RenderableLayer implements TileFactory {

    //protected TileFactory tiandituTileFactory;

    String urlAddress = "";

    public TiandituVecLayer() {
        this("http://t0.tianditu.com/DataServer");
    }

    public TiandituVecLayer(String serviceAddress) {
        if (serviceAddress == null) {
            throw new IllegalArgumentException(
                    Logger.logMessage(Logger.ERROR, "BlueMarbleLandsatLayer", "constructor", "missingServiceAddress"));
        }

        urlAddress = serviceAddress;
        //tiandituTileFactory = new WmtsTileFactory();

        // Configure this layer's level set to capture the entire globe at 15m resolution.
        double metersPerPixel = 15;
        double radiansPerPixel = metersPerPixel / WorldWind.WGS84_SEMI_MAJOR_AXIS;
        LevelSetConfig levelsConfig = new LevelSetConfig(null, 45, 16, 512, 256);
        //levelsConfig.numLevels = levelsConfig.numLevelsForResolution(radiansPerPixel);

        this.setDisplayName("TiandituSat");
        this.setPickEnabled(false);

        TiledSurfaceImage surfaceImage = new TiledSurfaceImage();
        surfaceImage.setLevelSet(new LevelSet(levelsConfig));
        surfaceImage.setTileFactory(this);
        surfaceImage.setImageOptions(new ImageOptions(WorldWind.RGB_565)); // reduce memory usage by using a 16-bit configuration with no alpha
        this.addRenderable(surfaceImage);

    }

    @Override
    public Tile createTile(Sector sector, Level level, int row, int column) {

        Sector sector1 = new Sector(sector.minLatitude(), sector.minLongitude() * 2 + 180, sector.deltaLatitude(), sector.deltaLongitude() * 2);
        ImageTile tile = new ImageTile(sector1, level, row, column);
        if(level.levelNumber>0){
          sector1 = new Sector(sector.minLatitude(), sector.minLongitude() , sector.deltaLatitude(), sector.deltaLongitude() * 2);
          tile = new ImageTile(sector1, level, row, column);
        }
        //urlAddress= "http://t0.tianditu.com/DataServer";
        //String urlString = urlAddress;//this.urlForTile(level.levelNumber, row, column);
        int row1 = (int) Math.pow(2, (level.levelNumber + 2)) - 1 - row;//计算行列和jishu
        int col1 = column;
        /*if(col1> Math.pow(2, (level.levelNumber + 2))-1){
            return null;
        }*/
       /* if(column%2!=0){
            return null;
        }else{
            col1 = column/2;
        }*/
        int level1 = level.levelNumber + 2;

        String serverURL = urlAddress.replaceFirst("0", String.valueOf((int) (Math.random() * 8)));//由于服务器端采用了集群技术，http://tile0/同http://tile7/取的是同一图片
        //瓦片URL串
        String urlString = serverURL + "?T=vec_w&x="+col1+"&y="+row1+"&l="+level1;

        if (urlString != null) {
            tile.setImageSource(ImageSource.fromUrl(urlString));
        }

        return tile;
    }
}

不过，由于投影的问题，加载的地图与worldwind的坐标系是不完全匹配的，所以，也只能通过这一过程来充分认识WorldWindAndroid加载切片的内在逻辑了！