前言：在開發過程中，經常會遇到各種座標的轉換，下面將實現幾個常用的座標的轉換：畫素座標、投影座標、經緯度座標

1.畫素座標
螢幕左上角為座標原點，向右為X軸正方向，向下為Y軸正方向，單位為px畫素

2.投影座標
WebGIS中以Mercator投影為主

Beijing 1954 3 Degree GK Zone 39意思是
3度分帶法的北京54座標系，中央經線在東117度的分帶座標，橫座標前加帶號

3.經緯度座標（地理座標）
Beijing54、Xian80、WGS84（WKID值為4326）等

你必須知道的地理座標系和投影座標系

WKID對照表

public class PointTransUtil {

//畫素點
static Point pixelsPoint =new Point(0.0,0.0);
//投影座標點
static Point projectPoint=new Point(0.0,0.0);
//經緯度點
static Point llPoint=new Point(0.0,0.0);

/**
 *
 * @param mPixelsPoint
 * @param mapView
 * @return
 */
public static Point pixelsPoint2ProjectPoint(Point mPixelsPoint, MapView mapView){

    projectPoint=mapView.toMapPoint((float) mPixelsPoint.getX(),(float) mPixelsPoint.getY());
    return projectPoint;
}

/**
 *
 * @param mProjectPoint
 * @param mapView
 * @return
 */
public static Point projectPoint2PixelsPoint(Point mProjectPoint, MapView mapView){

    pixelsPoint=mapView.toScreenPoint(mProjectPoint);
    return pixelsPoint;
}

/**
 *
 * @param mLlPoint
 * @param mapView
 * @param spatialReference
 * @return
 */
public static Point llPoint2ProjectPoint(Point mLlPoint, MapView mapView,SpatialReference spatialReference){

    projectPoint=(Point) GeometryEngine.project(mLlPoint ,spatialReference,mapView.getSpatialReference());
    return projectPoint;
}

/**
 *
 * @param mProjectPoint
 * @param mapView
 * @param spatialReference
 * @return
 */
public static Point projectPoint2LlPoint(Point mProjectPoint, MapView mapView,SpatialReference spatialReference){

    llPoint=(Point) GeometryEngine.project(mProjectPoint ,mapView.getSpatialReference(),spatialReference);
    return llPoint;
}

/**
 *
 * @param mPixelsPoint
 * @param mapView
 * @param spatialReference
 * @return
 */
public static Point pixelsPoint2LlPoint(Point mPixelsPoint, MapView mapView,SpatialReference spatialReference){

    llPoint=projectPoint2LlPoint(pixelsPoint2ProjectPoint(mPixelsPoint,mapView),mapView,spatialReference);
    return llPoint;
}

/**
 *
 * @param mLlPoint
 * @param mapView
 * @param spatialReference
 * @return
 */
public static Point llPoint2PixelsPoint(Point mLlPoint, MapView mapView,SpatialReference spatialReference){
    pixelsPoint=projectPoint2PixelsPoint(llPoint2ProjectPoint(mLlPoint,mapView,spatialReference),mapView);
    return pixelsPoint;
}
}