百度地图之收索视野内的建筑物-阿里云开发者社区

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

[delphi] view plain copy

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

[sql] view plain copy

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

[sql] view plain copy

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

[sql] view plain copy

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

[sql] view plain copy

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

[sql] view plain copy

--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

[sql] view plain copy

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

[java] view plain copy

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;
}
}
}
}

百度地图之收索视野内的建筑物

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