Multi-Map

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

UIKit

This example demonstrates how to use GEMKit in a UIKit application to display multiple maps simultaneously.

Check the full implementation on GitHub.

Multiple Maps Displayed

Multiple Map Display

The following code outlines the main view, which displays multiple maps and the action buttons to add a map and remove the last map:

ViewController.swiftView on GitHub

class ViewController: UIViewController {

    var index: CGFloat = 0
    var offsetTop: CGFloat = 0
    var offsetLeft: CGFloat = 0
    var size: CGFloat = 172

    override func viewDidLoad() {
        super.viewDidLoad()
        // Do any additional setup after loading the view.

        if let navigationController = self.navigationController {

            let appearance = navigationController.navigationBar.standardAppearance

            navigationController.navigationBar.scrollEdgeAppearance = appearance
        }

        var image = UIImage.init(systemName: "plus")
        let barButton1 = UIBarButtonItem.init(image: image, style: .done, target: self, action: #selector(buttonPlusPressed))

        image = UIImage.init(systemName: "minus")
        let barButton2 = UIBarButtonItem.init(image: image, style: .done, target: self, action: #selector(buttonMinusPressed))

        self.navigationItem.rightBarButtonItems = [barButton1]
        self.navigationItem.leftBarButtonItems = [barButton2]
    }

    // MARK: - Map View

    func createMapView() {

        self.offsetTop = 10 + self.index * 60.0 + 90
        self.offsetLeft = 10 + self.index * 40.0
        self.index += 1

        let mapViewController = MapViewController.init()
        mapViewController.view.backgroundColor = UIColor.systemBackground
        mapViewController.setCompassSize(20)

        mapViewController.view.layer.borderWidth = 1
        mapViewController.view.layer.borderColor = UIColor.darkGray.cgColor
        mapViewController.view.layer.cornerRadius = 8
        mapViewController.view.layer.shadowColor = UIColor.lightGray.cgColor
        mapViewController.view.layer.shadowOpacity = 0.8

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

        mapViewController.view.translatesAutoresizingMaskIntoConstraints = false
        NSLayoutConstraint.activate([
            mapViewController.view.topAnchor.constraint(equalTo: self.view.topAnchor, constant: self.offsetTop),
            mapViewController.view.leadingAnchor.constraint(equalTo: self.view.leadingAnchor, constant: self.offsetLeft),
            mapViewController.view.widthAnchor.constraint(equalToConstant: self.size),
            mapViewController.view.heightAnchor.constraint(equalToConstant: self.size)
        ])

        mapViewController.startRender()
    }

    func deleteMapView() {

        if let mapViewController = self.children.last as? MapViewController {

            mapViewController.stopRender()

            mapViewController.willMove(toParent: nil)
            mapViewController.view.removeFromSuperview()
            mapViewController.removeFromParent()

            self.index -= 1
        }
    }

    // MARK: - Button Action

    @objc func buttonPlusPressed(barButton: UIBarButtonItem) {

        self.createMapView()
    }

    @objc func buttonMinusPressed(barButton: UIBarButtonItem) {

        self.deleteMapView()
    }

    // MARK: - Render

    func startRender() {

        for viewController in self.children {

            if let mapView = viewController as? MapViewController {

                mapView.startRender()
            }
        }
    }

    func stopRender() {

        for viewController in self.children {

            if let mapView = viewController as? MapViewController {

                mapView.stopRender()
            }
        }
    }
}