//当前屏幕中心点的经纬度
CGFloat centerLongitude = self.mapView.region.center.longitude;
CGFloat centerLatitude = self.mapView.region.center.latitude;
//当前屏幕显示范围的经纬度
CLLocationDegrees pointssLongitudeDelta = self.mapView.region.span.longitudeDelta;
CLLocationDegrees pointssLatitudeDelta = self.mapView.region.span.latitudeDelta;
//左上角
CGFloat leftUpLong = centerLongitude - pointssLongitudeDelta/2.0;
CGFloat leftUpLati = centerLatitude - pointssLatitudeDelta/2.0;
//右上角
CGFloat rightUpLong = centerLongitude + pointssLongitudeDelta/2.0;
CGFloat rightUpLati = centerLatitude - pointssLatitudeDelta/2.0;
//左下角
CGFloat leftDownLong = centerLongitude - pointssLongitudeDelta/2.0;
CGFloat leftDownlati = centerLatitude + pointssLatitudeDelta/2.0;
//右下角
CGFloat rightDownLong = centerLongitude + pointssLongitudeDelta/2.0;
CGFloat rightDownLati = centerLatitude + pointssLatitudeDelta/2.0;
NSLog(@" 左上 %f,%f--------- 右上 %f,%f------- 左下 %f,%f----- 右下 %f,%f",leftUpLong,leftUpLati,rightUpLong,rightUpLati,leftDownLong,leftDownlati,rightDownLong,rightDownLati);