本文通过一个简单的小Demo，向大家介绍如何使用ArcGIS Android API绘制点、线、面图形，并且测量线的长度和多边形的面积。
首先来看一下程序运行的效果图：
实现上述功能，首先需要向地图中添加一个GraphicsLayer，用来绘制Point、Polyline、Polygon等Graphic对象。其次需要监听地图的Touch事件，即继承MapOnTouchListener类。最后调用Line或Polyline对象的calculateLength2D方法计算长度，调用Polygon对象的calculateArea2D的方法计算面积。
主要代码如下：
在main.xml布局文件中添加MapView控件：
<com.esri.android.map.MapViewandroid:id="@+id/map"android:layout_width="fill_parent"android:layout_height="fill_parent"initExtent = "11575115, 3575676, 11596612, 3599415" />在主Activity类中（本例是MeasureTestActivity.java）定义需要用到的全局变量：private MapView map;private GraphicsLayer drawLayer;private String strMapUrl="";private SimpleLineSymbol lineSymbol;private SimpleMarkerSymbol markerSymbol;private SimpleFillSymbol fillSymbol;private MapTouchListener mapTouchListener;在MeasureTestActivity类的onCreate方法中获取地图，添加图层：map = (MapView)findViewById(R.id.map);ArcGISTiledMapServiceLayer baseMapLayer = new ArcGISTiledMapServiceLayer(strMapUrl);map.addLayer(baseMapLayer);drawLayer = new GraphicsLayer();map.addLayer(drawLayer);还是在MeasureTestActivity类的onCreate方法中，添加对地图touch事件的监听：mapTouchListener = new MapTouchListener(MeasureTestActivity.this, map);map.setOnTouchListener(mapTouchListener);其中MapTouchListener类继承自MapOnTouchListener类，主要用于监听地图上的touch事件，包括onSingleTap和onDoubleTap事件。onSingleTap用于绘制点、绘制当前线段（并计算长度）、绘制现有点构成的临时多边形（并计算当前面积）；onDoubleTap用于结束绘制，并计算总长度和总面积。 class MapTouchListener extends MapOnTouchListener {private Geometry.Type geoType = null;//用于判定当前选择的几何图形类型private Point ptStart = null;//起点private Point ptPrevious = null;//上一个点private ArrayList<Point> points = null;//记录全部点private Polygon tempPolygon = null;//记录绘制过程中的多边形public MapTouchListener(Context context, MapView view) {super(context, view);points = new ArrayList<Point>();}// 根据用户选择设置当前绘制的几何图形类型public void setType(String geometryType) {if(geometryType.equalsIgnoreCase("Point"))this.geoType = Geometry.Type.Point;else if(geometryType.equalsIgnoreCase("Polyline"))this.geoType = Geometry.Type.Polyline;else if(geometryType.equalsIgnoreCase("Polygon"))this.geoType = Geometry.Type.Polygon;}public Geometry.Type getType() {return this.geoType;}@Overridepublic boolean onSingleTap(MotionEvent point) {Point ptCurrent = map.toMapPoint(new Point(point.getX(), point.getY()));if(ptStart == null) drawLayer.removeAll();//第一次开始前，，清空全部graphicif (geoType == Geometry.Type.Point) {//直接画点drawLayer.removeAll();ptStart = ptCurrent;Graphic graphic = new Graphic(ptStart,markerSymbol);drawLayer.addGraphic(graphic);btnClear.setEnabled(true);return true;}else//绘制线或多边形{points.add(ptCurrent);//将当前点加入点集合中if(ptStart == null){//画线或多边形的第一个点ptStart = ptCurrent;//绘制第一个点Graphic graphic = new Graphic(ptStart,markerSymbol);drawLayer.addGraphic(graphic);}else{//画线或多边形的其他点//绘制其他点Graphic graphic = new Graphic(ptCurrent,markerSymbol);drawLayer.addGraphic(graphic);//生成当前线段（由当前点和上一个点构成）Line line = new Line();line.setStart(ptPrevious);line.setEnd(ptCurrent);if(geoType == Geometry.Type.Polyline){//绘制当前线段Polyline polyline = new Polyline();polyline.addSegment(line, true);Graphic g = new Graphic(polyline, lineSymbol);drawLayer.addGraphic(g);// 计算当前线段的长度String length = Double.toString(Math.round(line.calculateLength2D())) + " 米";Toast.makeText(map.getContext(), length, Toast.LENGTH_SHORT).show();}else{//绘制临时多边形if(tempPolygon == null) tempPolygon = new Polygon();tempPolygon.addSegment(line, false);drawLayer.removeAll();Graphic g = new Graphic(tempPolygon, fillSymbol);drawLayer.addGraphic(g);//计算当前面积String sArea = getAreaString(tempPolygon.calculateArea2D());Toast.makeText(map.getContext(), sArea, Toast.LENGTH_SHORT).show();}}ptPrevious = ptCurrent;return true;}}@Overridepublic boolean onDoubleTap(MotionEvent point) {drawLayer.removeAll();if(bIsMeasureLength == true){Polyline polyline = new Polyline();Point startPoint = null;Point endPoint = null;// 绘制完整的线段for(int i=1;i<points.size();i++){startPoint = points.get(i-1);endPoint = points.get(i);Line line = new Line();line.setStart(startPoint);line.setEnd(endPoint);polyline.addSegment(line, false);}Graphic g = new Graphic(polyline, lineSymbol);drawLayer.addGraphic(g);// 计算总长度String length = Double.toString(Math.round(polyline.calculateLength2D())) + " 米";Toast.makeText(map.getContext(), length, Toast.LENGTH_SHORT).show();}else{Polygon polygon = new Polygon();Point startPoint = null;Point endPoint = null;// 绘制完整的多边形for(int i=1;i<points.size();i++){startPoint = points.get(i-1);endPoint = points.get(i);Line line = new Line();line.setStart(startPoint);line.setEnd(endPoint);polygon.addSegment(line, false);}Graphic g = new Graphic(polygon, fillSymbol);drawLayer.addGraphic(g);// 计算总面积String sArea = getAreaString(polygon.calculateArea2D());Toast.makeText(map.getContext(), sArea, Toast.LENGTH_SHORT).show();}// 其他清理工作btnClear.setEnabled(true);ptStart = null;ptPrevious = null;points.clear();tempPolygon = null;return false;}private String getAreaString(double dValue){long area = Math.abs(Math.round(dValue));String sArea = "";// 顺时针绘制多边形，面积为正，逆时针绘制，则面积为负if(area >= 1000000){double dArea = area / 1000000.0;sArea = Double.toString(dArea) + " 平方公里";}elsesArea = Double.toString(area) + " 平方米";return sArea;}}如需要完整代码，请在评论中留下邮箱。
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