从GeoFire查询添加注释只会丢弃一个引脚

Question

运行此GeoFire查询时，我只能让一个引脚留在地图上。它将所有这些都简单地放在了一起，但是剩下的就是最后一个。我希望所有注释留在地图上。这是代码：

if location != nil {
        let center = location.coordinate
        // Query location by region
        let span = MKCoordinateSpanMake(0.1, 0.1)
        let region = MKCoordinateRegionMake(center, span)
        regionQuery = geoFire?.query(with: region)


        queryHandle = regionQuery.observe(.keyEntered, with: { (key, location) in
           //print("Key '\(key)' entered the search area and is at location '\(location)'")


            self.annot.coordinate = (location!.coordinate)
            self.annot.title = key
            self.mapView.addAnnotation(self.annot)
            print(self.annot.coordinate)
           })

    queryHandle = regionQuery.observe(.keyExited, with: { (key, location) in
    })

}