基于百度SDK的地图软件开发心得.docx

基于百度地图SDK 的地图软件开发中的问题与注意事项（一） 最近我在研究基于百度地图SDK的安卓手机地图软件的开发。在百度地图SDK 官网上学习在地图图层上画自定义的几何图形是，我复制了demo中关于画矩形的代码，运行结果报错。经过一番研究发现示例demo中用Geometry的对象画一个矩形区域的时候，用的方法是setEnvelope，然而官网提供的sample中用的方法是setPolygon，修改为setPolygon后完美运行。 我自己写了一个简单的示例demo，我的Activity中有三个按钮，思路是点击第一个按钮后画线，点击第二个按钮后画多边形，点击第三个按钮后清除所有图层。我按照百度示例demo的代码编写完毕后运行，点击第一个按钮时可以画线，但当点击第二个画多边形的按钮后没有任何反应，当我再次点击第一个画线按钮后程序报错强退。这时我就纳闷了，因为百度提供的sample中的demo的代码和我差不多，然后我又看了一下官网的介绍。官网上关于GraphicsOverlay的介绍中提到，Geometry、Symbol、Graphic对象都不可复用，但是没有说GraphicsOverlay的对象，因此GraphicsOverlay的对象是可以复用的，简单分析下就能想到，GraphicsOverlay相当于一个图层，这个图层原则上是可以画很多图形的，因此我在两个按钮的单击事件中用的是同一个GraphicsOverlay对象。但是程序竟然报错了。于是我在两个按钮的单击事件中分别定义GraphicsOverlay对象，然后给各自的GraphicsOverlay对象setData()。再运行程序，愉快的解决了问题。 我再重新总结了我的代码和百度sample中提供的demo的区别，原来人家百度提供的demo的思路是单击一个按钮同时画多边形，线，矩形，因此提供一个GraphicsOverlay的对象足矣。而我的思路是画多边形和画线是在两个不同的事件中，不同的事件需要不同的GraphicsOverlay对象。如果只用一个GraphicsOverlay对象，程序就无法分辨我想要的是哪个GraphicsOverlay对象。 这只是一个小问题，因为我也是初学者，写下这篇文章权当给自己做个笔记，也提醒自己以后在学习的过程中不能盲目照搬。（附代码）package com.baidu.demo;import android.app.Activity;import android.os.Bundle;import android.view.View;import android.view.View.OnClickListener;import android.widget.Button;import com.baidu.mapapi.BMapManager;import com.baidu.mapapi.map.Geometry;import com.baidu.mapapi.map.Graphic;import com.baidu.mapapi.map.GraphicsOverlay;import com.baidu.mapapi.map.MapController;import com.baidu.mapapi.map.MapView;import com.baidu.mapapi.map.Symbol;import com.baidu.mapapi.map.Symbol.Color;import api.basestruct.GeoPoint;public class Mydrawdemo extends Activity BMapManager mBMapMan = null;MapView mMapView = null;Button drawline, myclear, drawrec = null;Overrideprotected void onCreate(Bundle savedInstanceState) super.onCreate(savedInstanceState);mBMapMan = new BMapManager(getApplication();mBMapMan.init(null);setContentView(R.layout.draw);mMapView = (MapView) findViewById(R.id.bmapView);mMapView.setBuiltInZoomControls(true);MapController mMapController = mMapView.getController();GeoPoint point = new GeoPoint(int) (39.915 * 1E6),(int) (116.404 * 1E6);mMapController.setCenter(point);mMapController.setZoom(12);drawline = (Button) findViewById(R.id.button2);myclear = (Button) findViewById(R.id.button1);drawrec = (Button) findViewById(R.id.button3);OnClickListener mylistener = new OnClickListener() Overridepublic void onClick(View v) / TODO Auto-generated method stubswitch (v.getId() case R.id.button3:GraphicsOverlay graphicsOverlay3 = new GraphicsOverlay(mMapView); mMapView.getOverlays().add(graphicsOverlay3);graphicsOverlay3.setData(drawrec();mMapView.refresh();break;case R.id.button2:GraphicsOverlay graphicsOverlay2 = new GraphicsOverlay(mMapView); mMapView.getOverlays().add(graphicsOverlay2);graphicsOverlay2.setData(drawline();mMapView.refresh();break;case R.id.button1:mMapView.getOverlays().clear();mMapView.refresh();break;drawline.setOnClickListener(mylistener);myclear.setOnClickListener(mylistener);drawrec.setOnClickListener(mylistener);protected Graphic drawrec() 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);GeoPoint polygonPoints = new GeoPoint5;polygonPoints0 = pt1;polygonPoints1 = pt2;polygonPoints2 = pt3;polygonPoints3 = pt4;polygonPoints4 = pt5;Geometry polygonGeometry = new Geometry();polygonGeometry.setPolygon(polygonPoints);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;protected 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 GeoPoint3;linePoints0 = pt1;linePoints1 = pt2;linePoints2 = 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;Overrideprotected void onPause() mMapView.onPause();super.onPause();Overrideprotected void onResume() mMapView.onResume();super.onResume();Overrideprotected void onDestroy() mMapView.destroy();super.onDestroy();Overrideprotected void onSaveI