topic AGSMapView.locationToScreen returns (nan,nan) in ArcGIS Runtime SDK for iOS Questions

AGSMapView.locationToScreen returns (nan,nan)

WorthSparks — Fri, 02 Feb 2018 23:27:13 GMT

My app displays spatially accurate graphics in a view on top of the mapView. To do so, I perform on-the-fly transformations for the graphics from within viewpointChangedHandler. Sometimes on first load, some of the graphics don't show on the screen where they should. After much debugging, I have discovered that even though the mapView.map has been loaded, calling mapView.locationToScreen() returns a CGPoint where both x and y are NaN, CGPoint(x: nan, y: nan).

The map is already AGSLoadStatusLoaded. But obviously, I'm trying to do this too soon. What trigger or observable on the mapView or mapView.map can I use to know when mapView.locationToScreen is ready to return good screen coordinates?

Re: AGSMapView.locationToScreen returns (nan,nan)

WorthSparks — Sat, 11 Dec 2021 20:33:18 GMT

In case anyone needs a workaround, this is what worked for me. It is crude, I know. But it works even on an iPhone 5s, which is the slowest device my app will run on.

self.map = AGSMap(item: portalItem)
self.map?.load {_ in
    // Even after the map load has completed, self.map is not ready
    // for any locationToScreen calls yet.
    Timer.scheduledTimer(withTimeInterval: 0.5, repeats: false) {_ in
        // But after waiting half a second, in all my tests, it is ready.
        // The following line triggers sketchView.draw(CGRect), which
        // calls this mapView's locationToScreen several times in pursuit
        // of sketch stroke transformations.
        self.sketchView.setNeedsDisplay()
    }
}‍‍‍‍‍‍‍‍‍‍‍‍‍‍‍‍‍‍‍‍‍‍‍‍‍‍‍‍‍‍‍‍‍‍‍‍‍‍‍‍‍‍‍‍‍‍‍‍‍‍‍‍‍‍‍‍‍‍

I'm not too keen on relying on a Timer for the solution. I'm hoping someone can tell me a better way.

Re: AGSMapView.locationToScreen returns (nan,nan)

DiveshGoyal — Tue, 13 Feb 2018 20:15:56 GMT

Try observing the AGSMapView#spatialReference property and wait till it is initialized. That should signal that the mapview has been properly setup to work with the provided map.

Re: AGSMapView.locationToScreen returns (nan,nan)

WorthSparks — Tue, 13 Feb 2018 23:02:41 GMT

Thanks, I'll try that and report back here. I'll bet that works.