62 lines
2.3 KiB
Markdown
62 lines
2.3 KiB
Markdown
# Blocking Gestures
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Constrain the map to a certain area.
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> Note: This example uses SwiftUI.
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To constrain the map to a certain area, you need to implement the ``MLNMapViewDelegate/mapView:shouldChangeFromCamera:toCamera:`` method of ``MLNMapViewDelegate``. By returning a boolean you can either allow or disallow a camera change.
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<!-- include-example(BlockingGesturesExample) -->
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```swift
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// Denver, Colorado
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private let center = CLLocationCoordinate2D(latitude: 39.748947, longitude: -104.995882)
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// Colorado’s bounds
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private let colorado = MLNCoordinateBounds(
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sw: CLLocationCoordinate2D(latitude: 36.986207, longitude: -109.049896),
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ne: CLLocationCoordinate2D(latitude: 40.989329, longitude: -102.062592)
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)
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struct BlockingGesturesExample: UIViewRepresentable {
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class Coordinator: NSObject, MLNMapViewDelegate {
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func mapView(_ mapView: MLNMapView, shouldChangeFrom _: MLNMapCamera, to newCamera: MLNMapCamera) -> Bool {
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// Get the current camera to restore it after.
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let currentCamera = mapView.camera
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// From the new camera obtain the center to test if it’s inside the boundaries.
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let newCameraCenter = newCamera.centerCoordinate
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// Set the map’s visible bounds to newCamera.
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mapView.camera = newCamera
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let newVisibleCoordinates = mapView.visibleCoordinateBounds
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// Revert the camera.
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mapView.camera = currentCamera
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// Test if the newCameraCenter and newVisibleCoordinates are inside self.colorado.
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let inside = MLNCoordinateInCoordinateBounds(newCameraCenter, colorado)
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let intersects = MLNCoordinateInCoordinateBounds(newVisibleCoordinates.ne, colorado) && MLNCoordinateInCoordinateBounds(newVisibleCoordinates.sw, colorado)
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return inside && intersects
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}
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}
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func makeUIView(context: Context) -> MLNMapView {
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let mapView = MLNMapView(frame: .zero, styleURL: VERSATILES_COLORFUL_STYLE)
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mapView.setCenter(center, zoomLevel: 10, direction: 0, animated: false)
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mapView.delegate = context.coordinator
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return mapView
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}
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func updateUIView(_: MLNMapView, context _: Context) {}
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func makeCoordinator() -> Coordinator {
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Coordinator()
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}
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}
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```
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The style used in this example can be found here: <doc:ExampleStyles>.
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