ios - 如何监控20多个区域？

Question

我正在开发一个有 66 个注释的应用程序。这些注释是区域的中心，每当用户进入一个区域时，都会出现一条通知，但这只适用于前 20 个区域，因为监视 regoins 的数量有限。我的问题是我不知道如何监控超过 20 个区域。谁能帮忙？

Answer 1

从你的 didUpdateLocations 设置 currentLocation

var currentLocation : CLLocation?{
    didSet{
        evaluateClosestRegions()
    }
}

var allRegions : [CLRegion] = [] // Fill all your regions

现在计算并找到离您当前位置最近的区域，并只跟踪这些区域。

func evaluateClosestRegions() {

    var allDistance : [Double] = []

    //Calulate distance of each region's center to currentLocation
    for region in allRegions{
        let circularRegion = region as! CLCircularRegion
        let distance = currentLocation!.distance(from: CLLocation(latitude: circularRegion.center.latitude, longitude: circularRegion.center.longitude))
        allDistance.append(distance)
    }
    // a Array of Tuples
    let distanceOfEachRegionToCurrentLocation = zip(allRegions, allDistance)

    //sort and get 20 closest
    let twentyNearbyRegions = distanceOfEachRegionToCurrentLocation
        .sorted{ tuple1, tuple2 in return tuple1.1 < tuple2.1 }
        .prefix(20)

    // Remove all regions you were tracking before
    for region in locationManager.monitoredRegions{
        locationManager.stopMonitoring(for: region)
    }

    twentyNearbyRegions.forEach{
        locationManager.startMonitoring(for: $0.0)
    }

}

为了避免 didSet 被调用太多次，我建议你适本地设置 distanceFilter (不要太大，这样你会捕捉到区域的回调太晚而不是太晚)小，这样你就不会运行冗余代码)。或者作为 this answer建议，只需使用 startMonitoringSignificantLocationChanges 来更新您的 currentLocation