Question

我有一个mapView，用户可以选择1英里，10英里，20英里和30英里的缩放半径，以从其设备所在的任何位置搜索餐厅。我已将所有餐厅的经纬度保存在GeoFire路径中。

当用户决定搜索时，首先获取用户的位置，然后让用户选择英里半径，然后将mapView缩放到该半径：

var selectedRadius = 0.0
let milesToMeters = 1609.344
let doubleDistance = 2  // according to this https://stackoverflow.com/a/5025970/4833705 to get a mapView radius of x miles, the distance needs to be doubled
var circleQuery: GFCircleQuery?
var queryHandle: UInt?

// 1. get the user's current location
guard let currentLocation = locationManager.location else { return }
let lat = currentLocation.coordinate.latitude
let lon = currentLocation.coordinate.longitude
let center = CLLocation(latitude: lat, longitude: lon)

// 2. user picks 10 mile radius
selectedRadius = (10 * doubleDistance) * milesToMeters

// 3. get the region I want to use for zoom in the mapView
let coordinateRegion = MKCoordinateRegionMakeWithDistance(center.coordinate, selectedRadius, selectedRadius)
mapView.setRegion(coordinateRegion, animated: true)

然后我想从GeoFire获得半径10英里范围内的所有餐厅，然后运行：

// 4. geoFire ref
let geofireRef = Database.database().reference().child("restaurant_locations")
let geoFire = GeoFire(firebaseRef: geofireRef)

// 5. since I had doubled the selectedRadius for the MKCoordinateRegionMakeWithDistance I now cut it in half to get the regular 10 mile radius in meters
let initialRadius = (selectedRadius / doubleDistance)

// 6. this is the radius I want to run the geoFire query on
circleQuery = geoFire?.query(at: center, withRadius: initialRadius)

// 7. observe .keyEntered at that query
queryHandle = circleQuery?.observe(.keyEntered, with: { (key: String!, location: CLLocation!) in ...

在步骤7中，当尝试观察.keyEntered时出现异常：

“精度必须小于23！

然后，我尝试使用GeoFire的Region查询query(with:)来设置跨度，但是抛出了完全相同的异常

let span = MKCoordinateSpanMake(initialRadius, initialRadius)
let region = MKCoordinateRegionMake(center.coordinate, span)
geoFire.query(with: region).observe(.keyEntered, with: { (key: String!, location: CLLocation!) in ...

选择10英里，20或30英里的MapView缩放半径时，如何运行GeoFire查询以匹配该半径？

Answer 1

我对海里给出的旧答案在地图上显示了错误的距离。

正确的方法是前往double the number of miles you want to span then multiple that by 1609.344（1英里为1609.344米），并将结果设置为CLLocationDistance以及您在MKCoordinateRegionMakeWithDistance()内的位置（下面的步骤3）

使用GFRegionQuery（下面的步骤6）代替GFCircleQuery来使用geoFire区域

基本上只是在下面的步骤2中进行转换，使用下面的步骤3中的区域，并将其设置为下面的步骤6中要使用的区域。

var radiusConversion = 0.0
let milesToMeters = 1609.344
let doubleDistance = 2
var regionQuery: GFRegionQuery?
var queryHandle: UInt?

// 1. get the user's current location
guard let currentLocation = locationManager.location else { return }
let lat = currentLocation.coordinate.latitude
let lon = currentLocation.coordinate.longitude
let center = CLLocation(latitude: lat, longitude: lon)

// 2. user picks 10 mile radius and do the conversion based on this link https://stackoverflow.com/a/5025970/4833705
radiusConversion = (10 * doubleDistance) * milesToMeters

// 3. set the region I want to use for zoom in the mapView
let region = MKCoordinateRegionMakeWithDistance(center.coordinate, radiusConversion, radiusConversion)
mapView.setRegion(region, animated: true) // zoom

// 4. geoFire ref
let geoFireRef = Database.database().reference().child("restaurant_locations")
let geoFire = GeoFire(firebaseRef: geoFireRef)

// 6. use GeoFire's query(with: region) and this is the radius I want to run the geoFire query on
regionQuery = geoFire.query(with: region)

// 7. observe.keyEntered at that region query
queryHandle = regionQuery?.observe(.keyEntered, with: {.observe(.keyEntered, with: { (key: String!, location: CLLocation!) in ...

// 8.
regionQuery?.observeReady {
    // do something when the observer from step 7 is finished
}

iOS -GeoFire ExceptionThrown'精度必须小于23！当搜索半径为宽

1 个答案: