MapKit:来自Sqlite数据库的坐标 [英] MapKit: coordinates from Sqlite database

问题描述

我有一个sqlite数据库，其中约有10万行，其中包含ATM的经度和纬度.我想通过MKMapView上的图钉显示此ATM.但是我认为如果一次从DB加载所有坐标，则对内存不利，而且速度也不快.最好的方法是什么?

I have a sqlite database with about 100 000 rows containing longitudes and latitudes of ATMs. I want to display this ATMs by pins on MKMapView. But I think that it is not good for memory and not o fast if I will load all coordinates from DB at once. What is the best way to do it?

推荐答案

您绝对正确，不要一次全部加载它们！

You're absolutely right, don't load them all at once!

使用边界框仅获取要显示的地图内的坐标.查看以下问题的答案:核心数据和核心位置

Use a bounding box to only get coordinates that are within the map your want to display. Check out the answer to this question : Core Data and Core Location

使用相同的上限和下限上限概念来仅返回来自sqlite的当前可见行.您的查询类似于

Use the same concept of a upper and lower limit to your lat and lng to only return rows from sqlite that are currently visible. Your query would look something like

SELECT * FROM atms WHERE lat > 51.4 and lat < 51.6 and lng > -0.165 and lng < -0.175

此查询仅返回位于伦敦市中心(51.5，-0.17)附近的ATM.

This query only returns ATMs that are near central London (51.5, -0.17).

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