android百度地图：在地图上绘制点、线、多边形、圆形和文字

首先介绍一个类：GraphicsOverlay

这是一个在地图上绘制图形的overlay。GraphicsOverlay通过调用setData(Graphic g) 完成图形绘制。

Graphic 通过构造方法Graphic(Geometry g, Symbol s) 获得。Geometry 是几何图形，而Symbol是几何图形的样式， 

设置线的样式：setLineSymbol(Symbol.Color color, int width) 

设置点的样式：setPointSymbol(Symbol.Color color)

设置面的样式：setSurface(Symbol.Color color, int status, int linewidth)

Geometry 就是一个几何图形，

绘制圆：setCircle(GeoPoint geoPoint, int radius)

绘制矩形：setEnvelope(GeoPoint geoPoint1, GeoPoint geoPoint2)

绘制点：setPoint(GeoPoint geoPoint, int pixel)

绘制多边形：setPolygon(GeoPoint[] geoPoints)

绘制线：setPolyLine(GeoPoint[] geoPoints)

2.1.2还新增了Textoverlay，可以在地图上添加文字。

TextOverlay textOverlay = new TextOverlay(mMapView);
        mMapView.getOverlays().add(textOverlay);
        textOverlay.addText(drawText()); //drawText()返回的是TextItem 类

具体来看看代码怎么写：

绘制线：

/**
     * 绘制折线，该折线状态随地图状态变化
     * @return 折线对象
     */
    public Graphic drawLine(){
    	double mLat = 39.97923;
       	double mLon = 116.357428;
       	
    	int lat = (int) (mLat*1E6);
	   	int lon = (int) (mLon*1E6);   	
	   	GeoPoint pt1 = new GeoPoint(lat, lon);
	   
	   	mLat = 39.94923;
       	mLon = 116.397428;
    	lat = (int) (mLat*1E6);
	   	lon = (int) (mLon*1E6);
	   	GeoPoint pt2 = new GeoPoint(lat, lon);
	   	mLat = 39.97923;
       	mLon = 116.437428;
		lat = (int) (mLat*1E6);
	   	lon = (int) (mLon*1E6);
	    GeoPoint pt3 = new GeoPoint(lat, lon);
	  
	    //构建线
  		Geometry lineGeometry = new Geometry();
  		//设定折线点坐标
  		GeoPoint[] linePoints = new GeoPoint[3];
  		linePoints[0] = pt1;
  		linePoints[1] = pt2;
  		linePoints[2] = pt3; 
  		lineGeometry.setPolyLine(linePoints);
  		//设定样式
  		Symbol lineSymbol = new Symbol();
  		Symbol.Color lineColor = lineSymbol.new Color();
  		lineColor.red = 255;
  		lineColor.green = 0;
  		lineColor.blue = 0;
  		lineColor.alpha = 255;
  		lineSymbol.setLineSymbol(lineColor, 10);
  		//生成Graphic对象
  		Graphic lineGraphic = new Graphic(lineGeometry, lineSymbol);
  		return lineGraphic;
    }

绘制多边形：

 /**
    * 绘制多边形，该多边形随地图状态变化
    * @return 多边形对象
    */
    public Graphic drawPolygon(){
    	double mLat = 39.93923;
       	double mLon = 116.357428;
    	int lat = (int) (mLat*1E6);
	   	int lon = (int) (mLon*1E6);   	
	   	GeoPoint pt1 = new GeoPoint(lat, lon);
	   	mLat = 39.91923;
       	mLon = 116.327428;
		lat = (int) (mLat*1E6);
	   	lon = (int) (mLon*1E6);
	    GeoPoint pt2 = new GeoPoint(lat, lon);
	    mLat = 39.89923;
       	mLon = 116.347428;
		lat = (int) (mLat*1E6);
	   	lon = (int) (mLon*1E6);
	    GeoPoint pt3 = new GeoPoint(lat, lon);
	    mLat = 39.89923;
       	mLon = 116.367428;
		lat = (int) (mLat*1E6);
	   	lon = (int) (mLon*1E6);
	    GeoPoint pt4 = new GeoPoint(lat, lon);
	    mLat = 39.91923;
       	mLon = 116.387428;
		lat = (int) (mLat*1E6);
	   	lon = (int) (mLon*1E6);
	    GeoPoint pt5 = new GeoPoint(lat, lon);
	    
	    //构建多边形
  		Geometry polygonGeometry = new Geometry();
  		//设置多边形坐标
  		GeoPoint[] polygonPoints = new GeoPoint[5];
  		polygonPoints[0] = pt1;
  		polygonPoints[1] = pt2;
  		polygonPoints[2] = pt3; 
  		polygonPoints[3] = pt4; 
  		polygonPoints[4] = pt5; 
  		polygonGeometry.setPolygon(polygonPoints);
  		//设置多边形样式
  		Symbol polygonSymbol = new Symbol();
 		Symbol.Color polygonColor = polygonSymbol.new Color();
 		polygonColor.red = 0;
 		polygonColor.green = 0;
 		polygonColor.blue = 255;
 		polygonColor.alpha = 126;
 		polygonSymbol.setSurface(polygonColor,1,5);
  		//生成Graphic对象
  		Graphic polygonGraphic = new Graphic(polygonGeometry, polygonSymbol);
  		return polygonGraphic;
    }

绘制点：

 /**
     * 绘制单点，该点状态不随地图状态变化而变化
     * @return 点对象
     */
    public Graphic drawPoint(){
       	double mLat = 39.98923;
       	double mLon = 116.397428;
    	int lat = (int) (mLat*1E6);
	   	int lon = (int) (mLon*1E6);   	
	   	GeoPoint pt1 = new GeoPoint(lat, lon);
	   	
	   	//构建点
  		Geometry pointGeometry = new Geometry();
  		//设置坐标
  		pointGeometry.setPoint(pt1, 10);
  		//设定样式
  		Symbol pointSymbol = new Symbol();
 		Symbol.Color pointColor = pointSymbol.new Color();
 		pointColor.red = 0;
 		pointColor.green = 126;
 		pointColor.blue = 255;
 		pointColor.alpha = 255;
 		pointSymbol.setPointSymbol(pointColor);
  		//生成Graphic对象
  		Graphic pointGraphic = new Graphic(pointGeometry, pointSymbol);
  		return pointGraphic;
    }

绘制圆：

 /**
     * 绘制圆，该圆随地图状态变化
     * @return 圆对象
     */
    public Graphic drawCircle() {
    	double mLat = 39.90923; 
       	double mLon = 116.447428; 
    	int lat = (int) (mLat*1E6);
	   	int lon = (int) (mLon*1E6);   	
	   	GeoPoint pt1 = new GeoPoint(lat, lon);
	   	
	   	//构建圆
  		Geometry circleGeometry = new Geometry();
  	
  		//设置圆中心点坐标和半径
  		circleGeometry.setCircle(pt1, 2500);
  		//设置样式
  		Symbol circleSymbol = new Symbol();
 		Symbol.Color circleColor = circleSymbol.new Color();
 		circleColor.red = 0;
 		circleColor.green = 255;
 		circleColor.blue = 0;
 		circleColor.alpha = 126;
  		circleSymbol.setSurface(circleColor,1,3);
  		//生成Graphic对象
  		Graphic circleGraphic = new Graphic(circleGeometry, circleSymbol);
  		return circleGraphic;
   }

绘制文字

/**
     * 绘制文字，该文字随地图变化有透视效果
     * @return 文字对象
     */
    public TextItem drawText(){
       	double mLat = 39.86923;
       	double mLon = 116.397428;
    	int lat = (int) (mLat*1E6);
	   	int lon = (int) (mLon*1E6);   	
	   	//构建文字
	   	TextItem item = new TextItem();
    	//设置文字位置
    	item.pt = new GeoPoint(lat,lon);
    	//设置文件内容
    	item.text = "百度地图SDK";
    	//设文字大小
    	item.fontSize = 40;
    	Symbol symbol = new Symbol();
    	Symbol.Color bgColor = symbol.new Color();
    	//设置文字背景色
    	bgColor.red = 0;
    	bgColor.blue = 0;
    	bgColor.green = 255;
    	bgColor.alpha = 50;
    	
    	Symbol.Color fontColor = symbol.new Color();
    	//设置文字着色
    	fontColor.alpha = 255;
    	fontColor.red = 0;
    	fontColor.green = 0;
    	fontColor.blue  = 255;
    	//设置对齐方式
    	item.align = TextItem.ALIGN_CENTER;
    	//设置文字颜色和背景颜色
    	item.fontColor = fontColor;
    	item.bgColor  = bgColor ; 
    	return item;
    }

添加到图层，显示在地图上：

GraphicsOverlay graphicsOverlay = new GraphicsOverlay(mMapView);
        mMapView.getOverlays().add(graphicsOverlay);
    	//添加点
        graphicsOverlay.setData(drawPoint());
    	//添加折线
        graphicsOverlay.setData(drawLine());
    	//添加多边形
        graphicsOverlay.setData(drawPolygon());
    	//添加圆
        graphicsOverlay.setData(drawCircle());
    	//绘制文字
        TextOverlay textOverlay = new TextOverlay(mMapView);
        mMapView.getOverlays().add(textOverlay);
        textOverlay.addText(drawText());
        //执行地图刷新使生效
        mMapView.refresh();

清除所有图层：

mMapView.getOverlays().clear();