从给定 MKMapView 的当前边界获取 latitude/longitude 度的大小

Question

Apple 开发者文档谈到 "map points" 获取当前显示的地图的可见部分。

什么是地图点？它与 latitude/longitude 度有什么关系？

Answer 1

什么是地图点？

From the MKMapPoint docs -

If you project the curved surface of the globe onto a flat surface, what you get is a two-dimensional version of a map where longitude lines appear to be parallel. Such maps are often used to show the entire surface of the globe all at once. An MKMapPoint data structure represents a point on this two-dimensional map.

The actual units of a map point are tied to the underlying units used to draw the contents of an MKMapView, but you should never need to worry about these units directly. You use map points primarily to simplify computations that would be complex to do using coordinate values on a curved surface. By converting to map points, you can perform those calculations on a flat surface, which is generally much simpler, and then convert back as needed. You can map between coordinate values and map points using the init(_:) and coordinate functions.

When saving map-related data to a file, you should always save coordinate values (latitude and longitude) and not map points.

它与 latitude/longitude 度有什么关系？

You can create a new MKMapPoint instance by using CLLocationCoordinate2D value(which can be created using latitude & longitude values.) See - MKMapPoint.init(_ coordinate:)

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对于 get the visible portion of the map that is currently displayed 部分，您可以使用 -

向 MKMapView 实例询问此信息

1. MKMapView.region

2. MKMapView.visibleMapRect

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更新

以下是计算 latitude 和 longitude 的 min/max 值的方法。

let region = mapView.region
let center = region.center
let span = region.span
let minLatitude = (center.latitude - span.latitudeDelta/2)
let maxLatitude = (center.latitude + span.latitudeDelta/2)
let minLongitude = (center.longitude - span.longitudeDelta/2)
let maxLongitude = (center.longitude + span.longitudeDelta/2)