如何在Android中删除Google地图上显示的路线？

Question

我的地图视图上有多个标记，当我单击标记时，它会显示从当前位置到标记的路线。

但是，当我单击下一个标记时，它会显示路线，但不会删除第一条路线。 在地图上绘制新路线时，如何删除第一条路线

我使用的代码是

在标记的单击侦听器中，我这样调用DrawPath方法：

    GeoPoint srcpoint = new GeoPoint(Source geopoint);

    GeoPoint destpoint = new GeoPoint(Destination geo point);

    DrawPath(srcpoint, destpoint, Color.GRAY, mapView);

DrawPath方法是：

  private void DrawPath(GeoPoint src, GeoPoint dest, int color,
          MapView mMapView01) {



        // connect to map web service
        StringBuilder urlString = new StringBuilder();
        urlString.append("http://maps.google.com/maps?f=d&hl=en");
        urlString.append("&saddr=");//from
        urlString.append( Double.toString((double)src.getLatitudeE6()/1.0E6 ));
        urlString.append(",");
        urlString.append( Double.toString((double)src.getLongitudeE6()/1.0E6 ));
        urlString.append("&daddr=");//to
        urlString.append( Double.toString((double)dest.getLatitudeE6()/1.0E6 ));
        urlString.append(",");
        urlString.append( Double.toString((double)dest.getLongitudeE6()/1.0E6 ));
        urlString.append("&ie=UTF8&0&om=0&output=kml");
        Log.d("xxx","URL="+urlString.toString());

        //System.out.println(urlString);
        // get the kml (XML) doc. And parse it to get the coordinates(direction route).
        Document doc = null;
        HttpURLConnection urlConnection= null;
        URL url = null;
        try
        {
          url = new URL(urlString.toString());
          urlConnection=(HttpURLConnection)url.openConnection();
          urlConnection.setRequestMethod("GET");
          urlConnection.setDoOutput(true);
          urlConnection.setDoInput(true);
          urlConnection.connect();

          DocumentBuilderFactory dbf = DocumentBuilderFactory.newInstance();
          DocumentBuilder db = dbf.newDocumentBuilder();
          doc = db.parse(urlConnection.getInputStream());

          if(doc.getElementsByTagName("GeometryCollection").getLength()>0)
          {
            //String path = doc.getElementsByTagName("GeometryCollection").item(0).getFirstChild().getFirstChild().getNodeName();
            String path = doc.getElementsByTagName("GeometryCollection").item(0).getFirstChild().getFirstChild().getFirstChild().getNodeValue() ;
            Log.d("xxx","path="+ path);
            String [] pairs = path.split(" ");
            String[] lngLat = pairs[0].split(","); // lngLat[0]=longitude lngLat[1]=latitude lngLat[2]=height
            // src
            GeoPoint startGP = new GeoPoint((int)(Double.parseDouble(lngLat[1])*1E6),(int)(Double.parseDouble(lngLat[0])*1E6));
            //mMapView01.getOverlays().add(overlayitem);
            GeoPoint gp1;
            GeoPoint gp2 = startGP;
            for(int i=1;i<pairs.length;i++) // the last one would be crash
            {
              lngLat = pairs[i].split(",");
              gp1 = gp2;
              // watch out! For GeoPoint, first:latitude, second:longitude
              gp2 = new GeoPoint((int)(Double.parseDouble(lngLat[1])*1E6),(int)(Double.parseDouble(lngLat[0])*1E6));
              mMapView01.getOverlays().add(new MapRouteOverlay(gp1,gp2,2,color));
              Log.d("xxx","pair:" + pairs[i]);
            }
            //mMapView01.getOverlays().add(new MapRouteOverlay(dest,dest, 3)); // use the default color
          }
        }
        catch (MalformedURLException e)
        {
          e.printStackTrace();
        }
        catch (IOException e)
        {
          e.printStackTrace();
        }
        catch (ParserConfigurationException e)
        {
          e.printStackTrace();
        }
        catch (SAXException e)
        {
          e.printStackTrace();
        }


      }

上述方法中使用的MapRouteOverlay.java类为：

      public class MapRouteOverlay extends Overlay {

     private GeoPoint gp1;
   private GeoPoint gp2;

   private int mode=0;
   private int defaultColor;




   public MapRouteOverlay(GeoPoint gp1,GeoPoint gp2,int mode) // GeoPoint is a int. (6E)
    {
      this.gp1 = gp1;
      this.gp2 = gp2;
      this.mode = mode;
     defaultColor = 999; // no defaultColor

  }

  public MapRouteOverlay(GeoPoint gp1,GeoPoint gp2,int mode, int defaultColor)
  {
    this.gp1 = gp1;
    this.gp2 = gp2;
    this.mode = mode;
    this.defaultColor = defaultColor;
  }

  public int getMode()
  {
    return mode;
  }

  public boolean draw
     (Canvas canvas, MapView mapView, boolean shadow, long when)
    {
       Projection projection = mapView.getProjection();

  if (shadow == false)
  {

    Paint paint = new Paint();
    paint.setAntiAlias(true);
    Point point = new Point();
    projection.toPixels(gp1, point);

    if(mode==2)
    {
      if(defaultColor==999)
        paint.setColor(Color.GRAY);
      else
        paint.setColor(Color.GRAY);
      Point point2 = new Point();
      projection.toPixels(gp2, point2);
      paint.setStrokeWidth(5);
      paint.setAlpha(120);
    //  canvas.restore();
      canvas.drawLine(point.x, point.y, point2.x,point2.y, paint);
    }

  }
  return super.draw(canvas, mapView, shadow, when);
}
}

用代码绘制新路径时如何删除第一个路径？

Answer 1

我认为您必须将要在for循环中创建的所有叠加层（MapRouteOverlay）保留在某种列表中，然后单击下一个叠加层时，必须将所有这些叠加层从地图中删除。 .....

Answer 2

正如我在您的代码中看到的那样，您将路线添加到

mMapView01.getOverlays().add(new MapRouteOverlay(gp1,gp2,2,color));

但是，您不会使用每次添加new关键字的new关键字删除旧路径，而是每次在地图叠加层中添加一条新路径时都会使用该关键字作为成员变量，然后在每次添加新路径之前都将其删除