MapView getting freezing for few seconds while loading thousands of data and zoom-in time in iOS

Question

I am developing Mapview in swift language. For, that I am loading geojson file into my mapview, its loading successfully. I am loading with GEOSwift library. Its working fine, but, what happening, While loading data, the mapview getting freeze/stuck for few seconds in UI, then later showing data. Even while Zooming time also freezing the UI few seconds.

I am loading LineString type data with coordinates around 7000 data.

Even I am doing parsing the data in background thread only.

I have two 3 tabs for loading different data in my map with 3 geojson

files. Even while switching one data to another data, its getting freezing.

In debugging are following error printing while zoomin/zoomout the mapview.

 [VKDefault] Tile 11720.7599.14 (128) in current unloaded state for 0.01 seconds - Raster Overlays Above Labels - Failed to decode (terminal) (0.01 sec)

My code is follows.

@IBAction func mapDataAction(_ sender: Any) {
        let overlays = mapView.overlays
        mapView.removeOverlays(overlays)

        self.mapView.removeAnnotations(mapView.annotations)


        DispatchQueue.global(qos: .background).async {
            if let geoJSONURL = Bundle.main.url(forResource: “LineString”, withExtension: "geojson") {
                do {
                    var overlays = [MKPolyline]()
                    let features = try Features.fromGeoJSON(geoJSONURL)
                    for item in features! {
                        if  let item = item.geometries![0] as? LineString {
                            let polyLine = item.mapShape() as! MKPolyline
                            overlays.append(polyLine)
                        }
                    }
                    DispatchQueue.main.async {
                        // add overlays to map
                        self.mapView.addOverlays(overlays)
                    }

                } catch {
                    //handle error
                }
            }
        }
    }

And one time app gets crashed with following message thrown in console.

Terminated due to memory issue

And its taking huge memory from cpu of device.

While scrolling the mapview or zoomin/zoomout its calling always the delegate method, this making freezing the mapview.

public func mapView(_ mapView: MKMapView, rendererFor overlay: MKOverlay) -> MKOverlayRenderer {
    if let polyline = overlay as? MKPolyline {
        let renderer = MKPolylineRenderer(polyline: polyline)
        //renderer.fillColor = UIColor.blue.withAlphaComponent(0.5)
        renderer.strokeColor = UIColor.blue.withAlphaComponent(0.8)
        renderer.lineWidth = 5
         print("MKPolylineRenderer delegate calling")
        return renderer
    }


    return MKOverlayRenderer(overlay: overlay)

 //   fatalError("Unexpected overlay type")
}

How can I solve this?

did you check what exactly takes time here? this parsing does not look like background thread — Lu_, Mar 19 '18 at 10:05
its printing this in debugging area [VKDefault] Tile 11720.7599.14 (128) in current unloaded state for 0.01 seconds - Raster Overlays Above Labels - Failed to decode (terminal) (0.01 sec) — Anilkumar iOS - ReactNative, Mar 19 '18 at 10:09
remove `do {` and use `let features = try! Features.fromGeoJSON(geoJSONURL)` — Lu_, Mar 21 '18 at 05:53
what exercise? what are you talking about? it just make your code slow — Lu_, Mar 21 '18 at 06:18
If I remove do { its throwing error at DispatchQueue.global(qos: .background).async { — Anilkumar iOS - ReactNative, Mar 21 '18 at 06:31
oh god, reamove everything that you added with `do {` there is also `catch` did you write that code? — Lu_, Mar 21 '18 at 06:34
Invalid conversion from throwing function of type '() throws -> ()' to non-throwing function type '@convention(block) () -> Void' throwing this error pls check this https://www.pastiebin.com/5ab1fe40c1613 — Anilkumar iOS - ReactNative, Mar 21 '18 at 06:40
While zooming/zoomout its getting freezing and the mapView(_ mapView: MKMapView, rendererFor overlay: MKOverlay delegate method calling — Anilkumar iOS - ReactNative, Mar 21 '18 at 07:01
so you need to measure everything what are you doing and then you will know what to improve — Lu_, Mar 21 '18 at 07:05
I am already doing parsing, then adding the data to mapview, that its, then why its happening freezing? — Anilkumar iOS - ReactNative, Mar 21 '18 at 07:09
Can you help me, while zoomin/zoomout why always this delegate methods calls? public func mapView(_ mapView: MKMapView, rendererFor overlay: MKOverlay) -> MKOverlayRenderer { — Anilkumar iOS - ReactNative, Mar 21 '18 at 07:37
because it needs to be called, if you use that it should be called when rendering — Lu_, Mar 21 '18 at 07:45
and you still didnt show which line exactly is taking time and freezing app — Lu_, Mar 21 '18 at 07:45
I already posted the delegate method is calling while zooming/zoomout the mapview, that one only making freeze the app. — Anilkumar iOS - ReactNative, Mar 21 '18 at 08:00
Let us [continue this discussion in chat](https://chat.stackoverflow.com/rooms/167240/discussion-between-anilkumar-ios-developer-and-lu). — Anilkumar iOS - ReactNative, Mar 21 '18 at 08:04
yes, it looks like whole app design is just bad and map is unreadable — Lu_, Mar 21 '18 at 08:23
i dont know the code and any of your measurements if it really is this delegate that is causing the problem — Lu_, Mar 21 '18 at 08:26
Yes, this delegate method calling frequently, thats why app makes freezing due to heavy data. — Anilkumar iOS - ReactNative, Mar 21 '18 at 09:15

MapView getting freezing for few seconds while loading thousands of data and zoom-in time in iOS

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