ArcGIS Runtime For Android 开发（4）

第四课 图形绘制

加载完地图以后，我们可能需要做一些数据采集的操作，那么绘制图形就非常的有用处了。在ArcGIS Runtime For Android 中，我们使用GraphicsLayer来承载绘制的图形。

我们先看一下绘制的逻辑：
地图中应该包含绘制层---------->GraphicsLayer
在界面上，点击按钮向系统发送命令-------->需要一个枚举类，存放命令
地图需要监听点击事件 ---------->OnSingleTapListener
每个图形需要一个默认的符号------>Symbol
图形是根据点来绘制的，所以需要保存图形的点数据------->List<Point>
那么接下来就简单了，根据ArcGIS Runtime For Android 提供的API，我们就可以完成图形的绘制。
首先，新建一个ActionCommand枚举类

public enum ActionCommand {
     NULL,                 //置空
    DRAW_POINT,           //绘制点
    DRAW_LINE,            //绘制线
    DRAW_POLYGON        //绘制面
}

在地图界面，实例化一个GraphicsLayer，并将这个GraphicsLayer加入到Map中；

GraphicsLayer drawLayer；
MapView mapView;
List<Point> tempDrawPoints;
PloyLine pPloyLine;
Ploygon pPloygon;
……
public void InitControl()
{
     mapView =(MapView) findViewById(R.id.mapView);
     mapView.setOnSingleTapListener(onSingleTap);
}
public InitData()
{
    String url ="https://services.arcgisonline.com/arcgis/rest/services/World_Imagery/MapServer"; 
    ArcGISTiledMapServiceLayer serviceLayer=new ArcGISTiledMapServiceLayer(url ); 
    mapView.addLayer(serviceLayer);//添加图层到地图窗口中
    drawLayer=new GraphicsLayer ();
    mapView.addLayer(drawLayer);
   tempDrawPoints=new ArrayList();
}

添加监听事件：

 OnSingleTapListener onSingleTapListener = new OnSingleTapListener() {

        @Override
        public void onSingleTap(float v, float v1) {
            Point pnt = mapView.toMapPoint(v, v1);
            switch (SystemManager.curAction) {
                case NULL: 
                    break;  
                case DRAW_POINT:
                    DrawPoint(pnt );
                    break;
                case DRAW_LINE: 
                    DrawLine(pnt );
                    break;
                case DRAW_POLYGON:  
                    DrawPolygon(pnt );
                    break; 
            }
        }
    };

然后是绘制图形：

public void DrawPoint(Point pnt)
{
       Graphic graphic = new Graphic(curPoint, simpleSymbol);
       drawLayer.addGraphic(graphic);
}
public void DrawLine(Point pnt)
{
    if (tempPoints.size() == 1) {
    Point point = tempDrawPoints.get(0);
    DrawPoint（point ）
} 
esle{
    drawLayer.removeAll();
    pPloyLine= new PloyLine();
    for (int i = 1; i < tempDrawPoints.size(); i++) {
        Point sPoint = tempDrawPoints.get(i - 1);
        Point ePoint = tempDrawPoints.get(i);
        Line line = new Line();
        line.setStart(sPoint);
        line.setEnd(ePoint);
        pPloyLine.addSegment(line, false);
    }
    Graphic polylineGraphic= new Graphic(pPloyLine,
                    MapManager.simpleLineSymbol);
    int UID=drawLayer.addGraphic(polylineGraphic);}
}
public void DrawPolygon()
{
    if (tempPoints.size() == 1) {
    Point point = tempDrawPoints.get(0);
     DrawPoint（point ）
    } 
   else {
            drawLayer.removeAll();
            pPolygon = new Polygon();
            for (int i = 1; i < tempDrawPoints.size(); i++) {
                Point sPoint = tempDrawPoints.get(i - 1);
                Point ePoint = tempDrawPoints.get(i);
                Line line = new Line();
                line.setStart(sPoint);
                line.setEnd(ePoint);
                pPolygon.addSegment(line, false);
            }
            Graphic polygonGraphic = new Graphic(pPolygon,
                    MapManager.simpleFillSymbolInspection);
            int UID=drawLayer.addGraphic(polygonGraphic);
        }
}