Android引路蜂地圖開發樣本：疊加自訂圖層

在開發應用的過程中，常常需要在地圖上需繪製一點自訂的興趣點或是自訂的幾何圖形。引路蜂地圖包中RasterMap最終提供的基實就是一張圖片。

[java] 
protected void paint(Graphics g){ 
    map.paint(mapGraphics); 
    g.drawImage((Image) mapImage.getNativeImage(), 0, 0, 0); 　　　　　　　 
    //start drawing your own sharps or images.  
    ... … 
    } 
protected void paint(Graphics g){
    map.paint(mapGraphics);
    g.drawImage((Image) mapImage.getNativeImage(), 0, 0, 0); 　　　　　　　
    //start drawing your own sharps or images.
    ... …
    }
所以一個簡單的方法是繪製完地圖後，你可以使用任何繪圖方法在地圖繪製任何自訂的圖形或是圖象。
這裡需要注意的是座標變換，RasterMap採用的是經緯度座標，而螢幕顯示採用的螢幕座標，RasterMap提供了座標轉換的方法：fromScreenPixelToLatLng　坐螢幕座標轉換成地圖經緯度座標。fromLatLngToScreenPixel　從經緯度座標轉換成螢幕座標。
下面給出的例子是採用派生MapLayer子類的方法，RasterMap是 MapLayerContainer的子類，可以用來管理多個地圖層。這些圖層從下到上相當於透明紙一層一層疊加形成最終顯示的地圖。
例子中顯示幾個自訂興趣點，和一個三角形，並中地圖中心顯示十字標。

[java] 
package com.pstreets.gisengine.demo; 
  
import com.mapdigit.gis.MapLayer; 
import com.mapdigit.gis.drawing.IGraphics; 
import com.mapdigit.gis.geometry.GeoLatLng; 
import com.mapdigit.gis.geometry.GeoPoint; 
import com.mapdigit.gis.raster.MapType; 
import com.pstreets.gisengine.GuidebeeMapView; 
import com.pstreets.gisengine.R; 
import com.pstreets.gisengine.SharedMapInstance; 
  
import android.app.Activity; 
import android.os.Bundle; 
  
public class MapOverlay extends Activity { 
  
  OverLayMapLayer mapLayer; 
 public void onCreate(Bundle savedInstanceState) { 
  super.onCreate(savedInstanceState); 
  setContentView(R.layout.main); 
 } 
  
 public void onStart() { 
  super.onStart(); 
  GeoLatLng center = new GeoLatLng(32.0616667, 118.7777778); 
  SharedMapInstance.map.setCenter(center, 9, MapType.MICROSOFTCHINA); 
  mapLayer = new OverLayMapLayer(SharedMapInstance.map.getScreenWidth(), 
    SharedMapInstance.map.getScreenHeight()); 
  SharedMapInstance.map.addMapLayer(mapLayer); 
  
 } 
   
 class OverLayMapLayer extends MapLayer { 
  
        GeoLatLng pt1 = new GeoLatLng(32.345281, 118.84261); 
        GeoLatLng pt2 = new GeoLatLng(32.05899, 118.62789); 
        GeoLatLng pt3 = new GeoLatLng(32.011811, 118.798656); 
  
        public OverLayMapLayer(int width, int height) { 
            super(width, height); 
        } 
  
        public void paint(IGraphics graphics, int offsetX, int offsetY) { 
            drawCursor(graphics); 
            drawTriangle(graphics); 
            drawPoint(graphics, pt1); 
            drawPoint(graphics, pt2); 
            drawPoint(graphics, pt3); 
  
        } 
  
        public void drawTriangle(IGraphics g) { 
            GeoPoint ptOnScreen1 = SharedMapInstance.map.fromLatLngToScreenPixel(pt1); 
            GeoPoint ptOnScreen2 = SharedMapInstance.map.fromLatLngToScreenPixel(pt2); 
            GeoPoint ptOnScreen3 = SharedMapInstance.map.fromLatLngToScreenPixel(pt3); 
            g.setColor(0xFF0000FF); 
             
            g.drawLine((int) ptOnScreen1.x, (int) ptOnScreen1.y, 
                    (int) ptOnScreen2.x, (int) ptOnScreen2.y); 
            g.drawLine((int) ptOnScreen2.x, (int) ptOnScreen2.y, 
                    (int) ptOnScreen3.x, (int) ptOnScreen3.y); 
            g.drawLine((int) ptOnScreen1.x, (int) ptOnScreen1.y, 
                    (int) ptOnScreen3.x, (int) ptOnScreen3.y); 
        } 
  
        public void drawPoint(IGraphics g, GeoLatLng pt) { 
            GeoPoint ptOnScreen = SharedMapInstance.map.fromLatLngToScreenPixel(pt); 
            int x = (int) ptOnScreen.x; 
            int y = (int) ptOnScreen.y; 
            g.setColor(0xFF00FF00); 
            g.fillRect(x - 4, y - 4, 8, 8); 
  
        } 
  
        private void drawCursor(IGraphics g) { 
             
            int mapWidth=getScreenWidth(); 
      int mapHeight=getScreenHeight(); 
      int x = mapWidth; 
      int y = mapHeight; 
            g.setColor(0xFF205020); 
            g.drawRect(x - 4, y - 4, 8, 8); 
            g.drawLine(x, y - 6, x, y - 2); 
            g.drawLine(x, y + 6, x, y + 2); 
            g.drawLine(x - 6, y, x - 2, y); 
            g.drawLine(x + 6, y, x + 2, y); 
        } 
    } 
  
} 
package com.pstreets.gisengine.demo;
 
import com.mapdigit.gis.MapLayer;
import com.mapdigit.gis.drawing.IGraphics;
import com.mapdigit.gis.geometry.GeoLatLng;
import com.mapdigit.gis.geometry.GeoPoint;
import com.mapdigit.gis.raster.MapType;
import com.pstreets.gisengine.GuidebeeMapView;
import com.pstreets.gisengine.R;
import com.pstreets.gisengine.SharedMapInstance;
 
import android.app.Activity;
import android.os.Bundle;
 
public class MapOverlay extends Activity {
 
  OverLayMapLayer mapLayer;
 public void onCreate(Bundle savedInstanceState) {
  super.onCreate(savedInstanceState);
  setContentView(R.layout.main);
 }
 
 public void onStart() {
  super.onStart();
  GeoLatLng center = new GeoLatLng(32.0616667, 118.7777778);
  SharedMapInstance.map.setCenter(center, 9, MapType.MICROSOFTCHINA);
  mapLayer = new OverLayMapLayer(SharedMapInstance.map.getScreenWidth(),
    SharedMapInstance.map.getScreenHeight());
  SharedMapInstance.map.addMapLayer(mapLayer);
 
 }
 
 class OverLayMapLayer extends MapLayer {
 
        GeoLatLng pt1 = new GeoLatLng(32.345281, 118.84261);
        GeoLatLng pt2 = new GeoLatLng(32.05899, 118.62789);
        GeoLatLng pt3 = new GeoLatLng(32.011811, 118.798656);
 
        public OverLayMapLayer(int width, int height) {
            super(width, height);
        }
 
        public void paint(IGraphics graphics, int offsetX, int offsetY) {
            drawCursor(graphics);
            drawTriangle(graphics);
            drawPoint(graphics, pt1);
            drawPoint(graphics, pt2);
            drawPoint(graphics, pt3);
 
        }
 
        public void drawTriangle(IGraphics g) {
            GeoPoint ptOnScreen1 = SharedMapInstance.map.fromLatLngToScreenPixel(pt1);
            GeoPoint ptOnScreen2 = SharedMapInstance.map.fromLatLngToScreenPixel(pt2);
            GeoPoint ptOnScreen3 = SharedMapInstance.map.fromLatLngToScreenPixel(pt3);
            g.setColor(0xFF0000FF);
           
            g.drawLine((int) ptOnScreen1.x, (int) ptOnScreen1.y,
                    (int) ptOnScreen2.x, (int) ptOnScreen2.y);
            g.drawLine((int) ptOnScreen2.x, (int) ptOnScreen2.y,
                    (int) ptOnScreen3.x, (int) ptOnScreen3.y);
            g.drawLine((int) ptOnScreen1.x, (int) ptOnScreen1.y,
                    (int) ptOnScreen3.x, (int) ptOnScreen3.y);
        }
 
        public void drawPoint(IGraphics g, GeoLatLng pt) {
            GeoPoint ptOnScreen = SharedMapInstance.map.fromLatLngToScreenPixel(pt);
            int x = (int) ptOnScreen.x;
            int y = (int) ptOnScreen.y;
            g.setColor(0xFF00FF00);
            g.fillRect(x - 4, y - 4, 8, 8);
 
        }
 
        private void drawCursor(IGraphics g) {
           
            int mapWidth=getScreenWidth();
      int mapHeight=getScreenHeight();
      int x = mapWidth;
      int y = mapHeight;
            g.setColor(0xFF205020);
            g.drawRect(x - 4, y - 4, 8, 8);
            g.drawLine(x, y - 6, x, y - 2);
            g.drawLine(x, y + 6, x, y + 2);
            g.drawLine(x - 6, y, x - 2, y);
            g.drawLine(x + 6, y, x + 2, y);
        }
    }
 
}

作者：mapdigit