Collect One: Native offline imagery download on Android and iOS

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Valutazione

Difficoltà
5/5
Tempo stimato
Più di una settimana
Idoneità per principianti
30/100
Tipo di issue
Funzionalità
Chiarezza
Specificata chiaramente
Stato di attività
Attiva
Stack tecnologico
android, ios, kotlin, swift
Ambito
mobile, mobile-dev

Direzione di ricerca

Start by reading the platform-neutral OfflineRegionStore API in shared/map, then inspect the Android entry points in shared/map/src/androidMain and the iOS bridge pattern in shared/map/src/iosMain and iosApp. Verify on a device or simulator using the stated Mapbox token and user data service URL; done means the acceptance criteria for downloads, offline rendering, cancellation, resume, and removal pass on both platforms.

Scritto dal modello di indicizzazione a partire dal testo della issue.

Descrizione

collect-one type: fr

Collect One mobile is getting a Save for offline flow:

  • Collectors pan and zoom to frame an area of up to 50 km² and choose Satellite, Terrain, or both.
  • They see the estimated size and the free space on the device, then save the imagery with a progress bar.
  • Saved areas are named by reverse geocoding and listed under Offline maps, with each imagery type shown as a separate layer.
  • The layers sheet gets two switches: Downloaded satellite and Downloaded terrain.

The shared UX, state and persistence are on branch feat/offline-area-download. Downloads go through a data-layer port, OfflineRegionClient (shared/app/data/.../client/offline/). Each host app supplies its implementation through platformModule(offlineRegionClient = …):

  • The browser build uses SimulatedOfflineRegionClient, with placeholder area names and a "Simulated download" notice, because Mapbox GL JS has no offline API.
  • Android and iOS default to UnavailableOfflineRegionClient, which hides the "Save an area" entry points.

This issue tracks real NATIVE clients for Android and iOS.

Scope

Android (shared/map/src/androidMain + androidApp)
  • Implement a NATIVE OfflineRegionClient with the Mapbox Maps SDK v11 TileStore and OfflineManager. The SDK lives in shared/map, so put the implementation there and adapt it to the port in androidApp (MobileSyncRuntime → platformModule(offlineRegionClient = …)):
    • Create one tile region per saved layer, using one style per layer:
      • Satellite: mapbox://styles/mapbox/satellite-streets-v12
      • Terrain: mapbox://styles/mapbox/outdoors-v12
    • Download each region for zoom 6–16 (always full zoom 16 detail), with pixelRatio set to the display density.
    • Store the area metadata on each region: area id, name, bounds, layer type, creation time and schema version.
    • Load a layer's style pack the first time that layer type is saved. Remove the style pack once no region uses it.
    • Estimate each layer with TileStore.estimateTileRegion (storage size, transfer size, error margin).
    • Report progress from TileRegionLoadProgress. Cancel through Cancelable, and resume by loading the same region id again.
    • List regions, including partial ones, so layers can be grouped into areas at launch.
    • Set MapboxOptions.accessToken from the app's configured token if no map has set it yet.
    • Map TileRegionError types to user-facing failures: tile-pack limit reached, disk full, access denied, and network unavailable.
  • First run the Android app on an emulator or device with a Mapbox token and a user data service URL. Then run the spike:
    • Confirm estimateTileRegion exists in 11.31.1.
    • Confirm the bounded mapbox://mapbox.satellite raster and the contour line overlay render from TileStore while offline.
    • Measure tile packs and bytes for a 50 km² save, then calibrate the simulated estimates and the area limit.
  • Verify against the acceptance criteria below.
iOS (shared/map/src/iosMain and iosApp)
  • Add a callback-based MapboxIosOfflineBridge interface that passes JSON in and out, following the existing MapboxIosView pattern.
  • Implement it in Swift with TileStore.default and OfflineManager, register it on GroundMapIos in iOSApp.init, and pass the adapter to platformModule from GroundMobileSyncIos.
  • Verify on a device or simulator once the iOS build is running again.

Acceptance criteria

  • Saving an area downloads the selected layers for zoom 6–16. The progress bar reaches 100%, and the area appears in Offline maps with each layer's size on disk.
  • With airplane mode on, and after force-stopping and reopening the app, each saved layer's basemap renders inside the area.
  • Downloaded satellite outlines satellite areas. On the Terrain basemap, it also shows the saved satellite imagery inside them.
  • Downloaded terrain outlines terrain areas. On the Satellite basemap, it also draws contour lines from the saved terrain data inside them.
  • Cancel removes partial data. Killing the app mid-save leaves the layer Paused, and Resume completes it.
  • Removing a layer frees its unshared data. Removing an area's last layer removes the area.
  • Area names come from Mapbox Geocoding v6 reverse lookups with permanent=true. If the lookup fails, a coordinate label is used instead.
  • Saving is blocked when the area exceeds 50 km² (about 7 × 7 km), or when the estimate plus a 500 MB reserve exceeds free space. Reaching Mapbox's tile-pack limit shows a clear message.

Constraints

  • Mapbox offline tile packs stop at zoom 16; imagery beyond zoom 16 is upscaled.
  • Mapbox allows 750 unique tile packs per device by default, shared across all saved layers.
  • Saved tiles render only for the exact style URIs and source URLs that were downloaded, so the overlays must reuse the styles' source URLs.
  • Satellite and Terrain share Mapbox's street tiles, so per-layer sizes can overlap.

Free-space measurement (DeviceStorageClient: StatFs on Android, NSFileManager on iOS) and the saved-areas table (SQLDelight) already exist on the branch.

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TypeScript
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