Map Render

_{Last updated: April 24, 2026 | 2 minutes read}

UIKit

This example demonstrates how to use GEMKit in a UIKit application to handle the map rendering based on the view controller's lifecycle.

Check the full implementation on GitHub.

MapViewController View

Map View Creation

MapViewController is embedded as a child and pinned to all edges. The compass is hidden immediately after creation:

ViewController.swiftView on GitHub

    func createMapView() {

        self.mapViewController = MapViewController.init()
        self.mapViewController!.view.backgroundColor = UIColor.systemBackground

        self.addChild(self.mapViewController!)
        self.view.addSubview(self.mapViewController!.view)
        self.mapViewController!.didMove(toParent: self)

        self.mapViewController!.hideCompass()

        self.mapViewController!.view.translatesAutoresizingMaskIntoConstraints = false
        NSLayoutConstraint.activate([
            self.mapViewController!.view.topAnchor.constraint(equalTo: self.view.topAnchor),
            self.mapViewController!.view.leadingAnchor.constraint(equalTo: self.view.leadingAnchor),
            self.mapViewController!.view.bottomAnchor.constraint(equalTo: self.view.bottomAnchor),
            self.mapViewController!.view.trailingAnchor.constraint(equalTo: self.view.trailingAnchor)
        ])
    }

Render Lifecycle

startRender() and stopRender() are called in the view controller's appearance callbacks to tie rendering to the screen visibility. The deinit calls destroy() to cleanly release the map resources:

ViewController.swiftView on GitHub

    deinit {

        if let controller = mapViewController {

            controller.destroy()
        }
    }

    override func viewWillAppear(_ animated: Bool) {

        super.viewWillAppear(animated)

        self.mapViewController!.startRender()
    }

    override func viewWillDisappear(_ animated: Bool) {

        super.viewWillDisappear(animated)

        self.mapViewController!.stopRender()
    }

SwiftUI

This example demonstrates how to use GEMKit in a SwiftUI application to handle the map rendering based on the app's lifecycle.

Check the full implementation on GitHub.

MapBase View

Map Display and Rendering

The following code outlines the main view, which displays the map and manages the rendering state based on the current scene phase:

ContentView.swiftView on GitHub

struct ContentView: View {
    
    @Environment(\.scenePhase) private var scenePhase
    
    @State private var isAppActive = true
    
    var body: some View {
        MapReader { proxy in
            MapBase(initialPosition: .amsterdam, initialZoomLevel: 54)
                .mapCompass(false)
                .mapRender(isAppActive)
        }
        .ignoresSafeArea()
        .onChange(of: scenePhase) { newPhase in
            switch newPhase {
            case .active:
                isAppActive = true
            case .background:
                isAppActive = false
            default:
                break
            }
        }
    }
}

info

This is the most basic example of controlling map rendering. Rendering can be toggled on and off at any time based on your app's specific needs, such as pausing rendering when the map is not fully visible or when UI smoothness is a priority, like with animations.