Preview Offline Map

The preview screen must register the active map style and may be configured to read tiles only from the cache. Focus the region bounds before enabling cache-only mode so local map data can be verified clearly.

Map preview:

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NBNavigation.registerOfflineMapStyle(
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    mapView: mapView,
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    styleURL: mapView.styleURL
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)
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_ = try NBNavigation.focusOfflineMapRegion(
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    mapView: mapView,
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    regionId: String(regionId)
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)
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NBNavigation.enableCacheOnlyPreview(mapView: mapView)
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// Restore network tile fetching when leaving cache-only preview.
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NBNavigation.disableCacheOnlyPreview(mapView: mapView)

If the routing catalog is available but the map catalog or installed map packages fail to load, the screen may still display a region row while the preview has missing tiles. Check the component error fields from fetchRegionLists and mapInstalledRegionList instead of treating a blank map as evidence that routing data was lost.