//清理坐标数据的视图和数据    [_bMapView removeAnnotations:_mapAnnotations];    [_mapAnnotations removeAllObjects];    [_carPointArray removeAllObjects];    //声明解析时对坐标数据的位置区域的筛选，包括经度和纬度的最小值和最大值    CLLocationDegrees minLat;    CLLocationDegrees maxLat;    CLLocationDegrees minLon;    CLLocationDegrees maxLon;    //解析数据    for (int i=0; i<rows.count; i++) {        NSDictionary *row = [rows objectAtIndex:i];        坐标模型类 *item = [[坐标模型类 alloc] initWithJson:row];        if (item.vehicleNo && [item.vehicleNo length]>0) {            标注模型类 *annotation = [[标注模型类 alloc] init];            annotation.coordinate = item.baiduCoordinate;            annotation.item = item;            [_mapAnnotations addObject:annotation];            [_bMapView addAnnotation:annotation];            [annotation release];                        if (i==0) {                //以第一个坐标点做初始值                minLat = item.baiduCoordinate.latitude;                maxLat = item.baiduCoordinate.latitude;                minLon = item.baiduCoordinate.longitude;                maxLon = item.baiduCoordinate.longitude;            }else{                //对比筛选出最小纬度，最大纬度；最小经度，最大经度                minLat = MIN(minLat, item.baiduCoordinate.latitude);                maxLat = MAX(maxLat, item.baiduCoordinate.latitude);                minLon = MIN(minLon, item.baiduCoordinate.longitude);                maxLon = MAX(maxLon, item.baiduCoordinate.longitude);            }                        [_carPointArray addObject:item];        }        [item release];    }    //动态的根据坐标数据的区域，来确定地图的显示中心点和缩放级别    if (_carPointArray.count > 0) {        //计算中心点        CLLocationCoordinate2D centCoor;        centCoor.latitude = (CLLocationDegrees)((maxLat+minLat) * 0.5f);        centCoor.longitude = (CLLocationDegrees)((maxLon+minLon) * 0.5f);        BMKCoordinateSpan span;        //计算地理位置的跨度        span.latitudeDelta = maxLat - minLat;        span.longitudeDelta = maxLon - minLon;        //得出数据的坐标区域        BMKCoordinateRegion region = BMKCoordinateRegionMake(centCoor, span);        //百度地图的坐标范围转换成相对视图的位置        CGRect fitRect = [_bMapView convertRegion:region toRectToView:_bMapView];        //将地图视图的位置转换成地图的位置        BMKMapRect fitMapRect = [_bMapView convertRect:fitRect toMapRectFromView:_bMapView];        //设置地图可视范围为数据所在的地图位置        [_bMapView setVisibleMapRect:fitMapRect animated:YES];            }

MKMapRect zoomRect = MKMapRectNull;for (id <MKAnnotation> annotation in mapView.annotations) {    MKMapPoint annotationPoint = MKMapPointForCoordinate(annotation.coordinate);    MKMapRect pointRect = MKMapRectMake(annotationPoint.x, annotationPoint.y, 0, 0);    if (MKMapRectIsNull(zoomRect)) {        zoomRect = pointRect;    } else {        zoomRect = MKMapRectUnion(zoomRect, pointRect);    }}[mapView setVisibleMapRect:zoomRect animated:YES];