Android实现在map上画出路线的方法

package net.blogjava.mobile.map; 
import java.util.List; 
import Android.app.AlertDialog; 
import android.graphics.Bitmap; 
import android.graphics.BitmapFactory; 
import android.graphics.Canvas; 
import android.graphics.Color; 
import android.graphics.Paint; 
import android.graphics.Path; 
import android.graphics.Point; 
import android.location.Address; 
import android.location.Geocoder; 
import android.os.Bundle; 
import android.view.Menu; 
import com.google.android.maps.GeoPoint; 
import com.google.android.maps.MapActivity; 
import com.google.android.maps.MapController; 
import com.google.android.maps.MapView; 
import com.google.android.maps.Overlay; 
import com.google.android.maps.Projection; 
public class Main extends MapActivity { 
private GeoPoint gpoint1, gpoint2, gpoint3;// 连线的点 
@Override 
public void onCreate(Bundle savedInstanceState) { 
 super.onCreate(savedInstanceState); 
 setContentView(R.layout.main); 
 MapView mapView = (MapView) findViewById(R.id.mapview); 
 mapView.setClickable(true); 
 mapView.setBuiltInZoomControls(true); 
 MapController mapController = mapView.getController(); 
 mapView.setTraffic(true);// 交通图 
 // mapView.setSatellite(true);//卫星图 
 // mapView.setStreetView(true);//街景 
 MyOverlay myOverlay = new MyOverlay(); 
 mapView.getOverlays().add(myOverlay); 
 mapController.setZoom(15);// 初始放大倍数 
 gpoint1 = new GeoPoint((int) (24.477384 * 1000000), 
 (int) (118.158216 * 1000000)); 
 gpoint2 = new GeoPoint((int) (24.488967 * 1000000), 
 (int) (118.144277 * 1000000)); 
 gpoint3 = new GeoPoint((int) (24.491091 * 1000000), 
 (int) (118.136781 * 1000000)); 
 mapController.animateTo(gpoint1); 
} 
@Override 
protected boolean isRouteDisplayed() { 
 // TODO Auto-generated method stub 
 return false; 
} 
class MyOverlay extends Overlay { 
 @Override 
 public void draw(Canvas canvas, MapView mapView, boolean shadow) { 
 // TODO Auto-generated method stub 
 super.draw(canvas, mapView, shadow); 
 // 画笔 
 Paint paint = new Paint(); 
 paint.setColor(Color.RED); 
 paint.setDither(true); 
 paint.setStyle(Paint.Style.STROKE); 
 paint.setStrokeJoin(Paint.Join.ROUND); 
 paint.setStrokeCap(Paint.Cap.ROUND); 
 paint.setStrokeWidth(2); 
 Projection projection = mapView.getProjection(); 
 Point p1 = new Point(); 
 Point p2 = new Point(); 
 Point p3 = new Point(); 
 projection.toPixels(gpoint1, p1); 
 projection.toPixels(gpoint2, p2); 
 projection.toPixels(gpoint3, p3); 
 Path path = new Path(); 
 path.moveTo(p1.x, p1.y); 
 path.lineTo(p2.x, p2.y); 
 path.lineTo(p3.x, p3.y); 
 canvas.drawPath(path, paint);// 画出路径 
 } 
} 
}

<?xml version="1.0" encoding="utf-8"?> 
<LinearLayout xmlns:Android="http://schemas.android.com/apk/res/android" 
 android:orientation="vertical" android:layout_width="fill_parent" 
 android:layout_height="fill_parent"> 
 <com.google.android.maps.MapView 
 android:id="@+id/mapview" android:layout_width="fill_parent" 
 android:layout_height="fill_parent" 
 android:apiKey="0IB7Kn70qp1LT216Hhb-jmHJ8GLTie4p63O77KQ" /> 
</LinearLayout>

/** 
* 通过解析google map返回的xml，在map中画路线图
*/ 
public void drawRoute(){
 String url = "http://maps.google.com/maps/api/directions/xml?origin=23.055291,113.391802" + "&destination=23.046604,113.397510&sensor=false&mode=walking"; 
 HttpGet get = new HttpGet(url); 
 String strResult = ""; 
 try { 
  HttpParams httpParameters = new BasicHttpParams(); 
  HttpConnectionParams.setConnectionTimeout(httpParameters, 3000); 
  HttpClient httpClient = new DefaultHttpClient(httpParameters); 
  HttpResponse httpResponse = null; 
  httpResponse = httpClient.execute(get); 
  if (httpResponse.getStatusLine().getStatusCode() == 200){ 
  strResult = EntityUtils.toString(httpResponse.getEntity()); 
  } 
 } catch (Exception e) { 
  return; 
 } 
 if (-1 == strResult.indexOf("<status>OK</status>")){ 
  Toast.makeText(this, "获取导航路线失败!", Toast.LENGTH_SHORT).show(); 
  this.finish(); 
  return; 
 } 
 int pos = strResult.indexOf("<overview_polyline>"); 
 pos = strResult.indexOf("<points>", pos + 1); 
 int pos2 = strResult.indexOf("</points>", pos); 
 strResult = strResult.substring(pos + 8, pos2); 
 List<GeoPoint> points = decodePoly(strResult); 
 MyOverLay mOverlay = new MyOverLay(points); 
 List<Overlay> overlays = mMapView.getOverlays(); 
 overlays.add(mOverlay); 
 if (points.size() >= 2){ 
  mMapController.animateTo(points.get(0)); 
 } 
 mMapView.invalidate(); 
 } 
/** 
* 解析返回xml中overview_polyline的路线编码 
* 
* @param encoded 
* @return 
*/ 
private List<GeoPoint> decodePoly(String encoded) { 
 List<GeoPoint> poly = new ArrayList<GeoPoint>(); 
 int index = 0, len = encoded.length(); 
 int lat = 0, lng = 0; 
 while (index < len) { 
  int b, shift = 0, result = 0; 
  do { 
  b = encoded.charAt(index++) - 63; 
  result |= (b & 0x1f) << shift; 
  shift += 5; 
  } while (b >= 0x20); 
  int dlat = ((result & 1) != 0 ? ~(result >> 1) : (result >> 1)); 
  lat += dlat; 
  shift = 0; 
  result = 0; 
  do { 
  b = encoded.charAt(index++) - 63; 
  result |= (b & 0x1f) << shift; 
  shift += 5; 
  } while (b >= 0x20); 
  int dlng = ((result & 1) != 0 ? ~(result >> 1) : (result >> 1)); 
  lng += dlng; 
  GeoPoint p = new GeoPoint((int) (((double) lat / 1E5) * 1E6),(int) (((double) lng / 1E5) * 1E6)); 
  poly.add(p); 
 } 
 return poly; 
}