百度地图查询视野范围内的建筑物

   根据用户移动地图的位置，显示在视野范围内的建筑物，简单的思路是，添加地图监听，当地图移动结束之后，计算出当前屏幕四个角的GeoPoint，根据这4个点，通过mysql的spatial中的函数，完成在此范围内的建筑物的查询。

1.   mysql spatial介绍

  从MySQL4.0开始加入了Spatial扩展功能，实现了OpenGIS规定的几何数据类型，在SQL中的简单空间运算。但是MySQL对空间查询的支持不够完善，要进行复杂的空间运算，建议使用postgreSQL数据库的postGIS。

    下图是MySQL Spatial接口及类的结构(有背景颜色的框代表接口）：

    有关mysql的详细介绍，可以参考一下链接中的文章。

l  官方参考文档（中文）：

http://dev.mysql.com/doc/refman/5.1/zh/spatial-extensions-in-mysql.html#mysql-spatial-datatypes

l  官方参考文档（英文）：

http://dev.mysql.com/doc/refman/5.0/en/spatial-extensions.html

l  关于hibernate支持mysql-spatial：

http://blog.csdn.net/b10090120/article/details/8698787

http://www.hibernatespatial.org/tutorial.html

拓展mysqlspatial函数：

1)  空间中的点是否相等

DELIMITER $$     CREATE DEFINER = 'smart'@'localhost'  FUNCTION ArePointsEqual(p1 POINT,                          p2POINT                          )  RETURNS TINYINT(1)  DETERMINISTIC  NO SQL  BEGIN    RETURN IsZero(x(p1) -x(p2)) AND IsZero(y(p1) - y(p2));  END  $$     DELIMITER ;

2)  查找区域的中心点

USE smartu;     DELIMITER $$     CREATE DEFINER = 'smart'@'localhost'  FUNCTION GetCenterPoint(g GEOMETRY)  RETURNS POINT  DETERMINISTIC  NO SQL  BEGIN    DECLARE envelope  POLYGON;    DECLARE sw, ne    POINT; #South-West and North-East points    DECLARE lat, lng  DOUBLE;       SET envelope =exteriorring(Envelope(g));    SET sw =pointn(envelope, 1);    SET ne =pointn(envelope, 3);    SET lat = x(sw) + (x(ne)- x(sw)) / 2;    SET lng = y(sw) + (y(ne)- y(sw)) / 2;    RETURN POINT(lat, lng);  END  $$     DELIMITER ;

3)  LineN

USE smartu;     DELIMITER $$     CREATE DEFINER = 'smart'@'localhost'  FUNCTION LineN(ls LINESTRING,                 n  INT                 )  RETURNS LINESTRING  DETERMINISTIC  NO SQL  BEGIN    IF n >= numpoints(ls)THEN      RETURN NULL;    END IF;    RETURNLineString(pointn(ls, n), pointn(ls, n + 1));  END  $$     DELIMITER ;

4)  计算两点间的空间距离

USE smartu;     DELIMITER $$     CREATE DEFINER = 'smart'@'localhost'  FUNCTION DISTANCE(lat1 DOUBLE,                    lon1DOUBLE,                    lat2DOUBLE,                    lon2DOUBLE                    )  RETURNS DOUBLE  DETERMINISTIC  NO SQL  COMMENT 'counts distance (km) between 2 points on Earth surface'  BEGIN    DECLARE dtor DOUBLEDEFAULT 57.295800;       RETURN (6371 *acos(sin(lat1 / dtor) * sin(lat2 / dtor) +    cos(lat1 / dtor) *cos(lat2 / dtor) *    cos(lon2 / dtor - lon1 /dtor)));  END  $$     DELIMITER ;

5)  是否为0

USE smartu;     DELIMITER $$     CREATE DEFINER = 'smart'@'localhost'  FUNCTION IsZero(n DOUBLE)  RETURNS TINYINT(1)  DETERMINISTIC  NO SQL  BEGIN    DECLARE epsilon DOUBLEDEFAULT 0.00000000001;       RETURN (abs(n) <=epsilon);  END  $$     DELIMITER ;

2.  项目前台、后台的实现

1)  项目后台实现

l  数据库设计

--创建表  createtable smart_u_convenience_item_spatial(      item_spatial_id varchar(36) not null,      location point not null,      latitude varchar(20),      longitude varchar(20),      convenience_item_code varchar(500),      convenience_item_name varchar(500),      primary key (`item_spatial_id`),      spatial key `sp_index`(location)  )ENGINE=MyISAM;  --往表中插入数据  INSERTINTO smart_u_convenience_item_spatial  SELECTt.convenience_item_id       , PointFromText(concat('POINT(',t.item_latitude, ' ', t.item_longitude, ')'))       , t.item_latitude       , t.item_longitude       , t.convenience_item_code       , t.convenience_item_name     from smart_u_convenience_item t;

l  后台代码使用到的查询点的sql

SELECT *  FROM    (SELECT *     FROM      smart_u_convenience_item t     WHERE       t.convenience_item_idIN      (SELECTs.item_spatial_id         FROM          smart_u_convenience_item_spatial s         WHERE          intersects(location,                     geomfromtext(concat('POLYGON((', 3.9921123E7, ' ', 1.16365462E8,                                                  ',', 3.9921123E7, ' ', 1.16441881E8,                                                 ',', 3.9879484E7, ' ', 1.16441881E8,                                                 ',', 3.9879484E7, ' ', 1.16365462E8,                                                   ',', 3.9921123E7, ' ', 1.16365462E8,'))'))))) t  ORDER BY   item_longitude ASC

2)  前台设计

MKMapViewListener mapViewListener = new MKMapViewListener() {              @Override           public void onMapMoveFinish() {              // 此处可以实现地图移动完成事件的状态监听              Log.e(TAG,"mapMoveFinish");             BsnsDisAllActivity.this.getBsnsDisInfo(BsnsDisAllActivity.this.getGeoPointMap());                      }              @Override           public void onClickMapPoi(MapPoipoi) {              Log.e(TAG,poi.geoPt.getLatitudeE6()+","+poi.geoPt.getLongitudeE6());                    }              @Override           public void onGetCurrentMap(Bitmaparg0) {              Log.e(TAG,"onGetCurrentMap");                        }              @Override           public void onMapAnimationFinish(){              Log.e(TAG,"onMapAnimationFinish");             BsnsDisAllActivity.this.getBsnsDisInfo(BsnsDisAllActivity.this.getGeoPointMap());           }        };        mMapView.regMapViewListener(app.mBMapManager,mapViewListener);     private Map<String,Double> getGeoPointMap(){              Projectionprojection = mMapView.getProjection();              Map<String,Double>polygon = newHashMap<String,Double>();           GeoPointtop = projection.fromPixels(0, 0);           polygon.put("top_x",(double) top.getLatitudeE6());           polygon.put("top_y",(double)top.getLongitudeE6());           GeoPointright = projection.fromPixels(mMapView.getWidth(), 0);           polygon.put("right_x",(double)right.getLatitudeE6());           polygon.put("right_y",(double)right.getLongitudeE6());           GeoPointdown = projection.fromPixels(mMapView.getWidth(), mMapView.getHeight());           polygon.put("down_x",(double)down.getLatitudeE6());           polygon.put("down_y",(double)down.getLongitudeE6());           GeoPointleft = projection.fromPixels(0, mMapView.getHeight());           polygon.put("left_x",(double)left.getLatitudeE6());           polygon.put("left_y",(double)left.getLongitudeE6());                     return polygon;        }        private voidgetBsnsDisInfo(Map<String,Double>polygon){            final Map<String,Double> tPolygon =polygon;           new Thread(){              public void run() {                  try{                     List<OrderByEntity>orderByEntity = new ArrayList();                     OrderByEntityorder = newOrderByEntity();                     order.setOrderCol("item_longitude");                     order.setOrderType("asc");                     orderByEntity.add(order);     //              OrderByEntityorder2 = new OrderByEntity();     //              order.setOrderCol("item_latitude");     //              order.setOrderType("asc");     //              orderByEntity.add(order2);                         ConvenienceItemAckEntityack = SUService.getInstance().getMapBsns(app.nowUser, tPolygon, orderByEntity, null, null);                     Log.i(TAG,ack.getAckCode().toString());                     Log.i(TAG,ack.getAckMsg().toString());                    Message msg = new Message();                     if(ack.getAckCode().toString().indexOf("INFO") != -1){                        msg.what = RESULT_BSNS_CAT;                     }else{                        msg.what = RESULT_ERROR;                     }                     msg.obj = ack;                     myHandler.sendMessage(msg);                  }catch(Exception e){                                      }                               };           }.start();        }                 Handler myHandler = new Handler(){           public void handleMessage(Messagemsg) {              switch (msg.what) {              case RESULT_BSNS_CAT:                  ConvenienceItemAckEntityack = (ConvenienceItemAckEntity)msg.obj;                  pinItemMark(ack.getResults());                  break;                 default:                  break;              }           };        };               private voidpinItemMark(List<ConvenienceItemEntity> itemList){           convenieceItemList= newArrayList<ConvenienceItemEntity>();           mGeoList.clear();           latLoc.clear();           for(inti=0;i<itemList.size();i++){              ConvenienceItemEntityitemEntity = itemList.get(i);              int lat = Integer.parseInt(itemEntity.getItemLatitude());              int loc = Integer.parseInt(itemEntity.getItemLongtude());              OverlayItemitem = newOverlayItem(newGeoPoint(lat, loc),itemEntity.getConvenienceItemName() ,itemEntity.getConvenienceItemId());                           ViewdrawableView = LayoutInflater.from(BsnsDisAllActivity.this).inflate(                     R.layout.map_drawable_pin, null);// 获取要转换的View资源              TextViewTestText = (TextView)drawableView.findViewById(R.id.map_drawable_text);              TestText.setText(item.getTitle());//将每个点的Title在弹窗中以文本形式显示出来                                BitmapdrawableBitmap = convertViewToBitmap(drawableView);                           Drawabledraw = newBitmapDrawable(drawableBitmap);                     item.setMarker(draw);                           convenieceItemList.add(itemEntity);              mGeoList.add(item);              PointlocPoint = newPoint();              locPoint.x = i+1;              locPoint.y = lat;              latLoc.add(locPoint);                    }                     addMarker(mGeoList);           for (int i = 0; i < latLoc.size(); i++){                    for (int j = 1; j < latLoc.size() - i; j++) {                     Point p1 = latLoc.get((j-1));                     Point p2 = latLoc.get(j);                                          if(p1.y>p2.y){                        Point temp = p1;                        latLoc.set(j-1, p2);                        latLoc.set(j, p1);                     }                     if(latLoc.get(j-1).x==0){                        selectedItemLat = j-1;                     }                   }           }        }

来自：http://blog.csdn.net/fengshuiyue/article/details/9155463