AGSMapView.locationToScreen returns (nan,nan)

Question

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?

WorthSparks · Answer

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

DiveshGoyal · Answer

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.

WorthSparks · Answer

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.