maui-device-capabilities

name

maui-device-capabilities

description

Implement .NET MAUI device capabilities with platform permissions and declarations. USE FOR: camera/photo/media capture, MediaPicker.IsCaptureSupported, FilePicker.PickAsync durable copies to FileSystem.AppDataDirectory, GeolocationRequest, Permissions.LocationWhenInUse, UseMauiMaps, Android manifest entries, READ_MEDIA_IMAGES/Android 13+ Photo Picker migration, NSCameraUsageDescription/NSLocationWhenInUseUsageDescription, runtime permission requests, denied/cancelled flows, and durable file access. DO NOT USE FOR: notifications, auth, or UI layout.

MAUI Device Capabilities

Use this skill when a MAUI app needs device services such as files, media, camera, location, or maps. Always pair runtime API calls with platform declarations and a user-friendly denied/cancelled path.

Workflow

1. Inspect target platforms and existing files under Platforms/Android, Platforms/iOS, Platforms/MacCatalyst, and Platforms/Windows.
2. Identify the exact capability and minimum permission needed.
3. Add platform declarations before requesting runtime permissions.
4. Request permissions close to the feature that needs them, after explaining why the app needs access.
5. Treat cancellation as normal user choice.
6. Keep device APIs behind services if ViewModels or tests should not depend on MAUI static APIs directly.
7. Validate on every target platform because permission names and UX differ.

Permission Pattern

var status = await Permissions.CheckStatusAsync<Permissions.LocationWhenInUse>();

if (status != PermissionStatus.Granted)
{
    status = await Permissions.RequestAsync<Permissions.LocationWhenInUse>();
}

if (status != PermissionStatus.Granted)
{
    PermissionDeniedMessage = "Location is off. Enable it in Settings to show nearby stores.";
    CanOpenSettings = true;
    SemanticScreenReader.Announce(PermissionDeniedMessage);
    return;
}

Do not repeatedly prompt after a user denies access. Show a feature-specific empty/blocked state that screen readers can observe, and when appropriate guide the user to app settings with an explicit button that calls AppInfo.ShowSettingsUI().

Platform Declaration Map

Capability	Android	iOS/Mac Catalyst
Camera/media capture	CAMERA and media storage permissions only when needed by target SDK behavior	NSCameraUsageDescription, NSMicrophoneUsageDescription, NSPhotoLibraryUsageDescription as applicable
Gallery/media library access	On Android 12 and earlier, audit READ_EXTERNAL_STORAGE; on Android 13+ use granular READ_MEDIA_IMAGES, READ_MEDIA_VIDEO, or READ_MEDIA_AUDIO as applicable, or prefer the system photo picker when it satisfies the scenario	NSPhotoLibraryUsageDescription or limited-library APIs when reading the photo library
Geolocation	ACCESS_COARSE_LOCATION, ACCESS_FINE_LOCATION, and background location only for true background scenarios	NSLocationWhenInUseUsageDescription; add always/background keys only when the app truly needs them
File picking	Usually no broad storage permission for system picker flows	Document picker usually needs no photo/camera usage key unless media capture/library access is used
Maps	Platform API key/configuration and UseMauiMaps() when using MAUI Maps	Platform map entitlement/configuration as required by the map provider

Use the narrowest platform declaration that matches the feature. Do not add background location, broad storage, or microphone declarations "just in case".

Picker and Sensor Guardrails

• FilePicker.PickAsync and PickMultipleAsync should handle null, empty results, cancellation, and PermissionException.
• MediaPicker should check IsCaptureSupported before camera capture.
• Copy picked file streams into app storage when the app needs durable access; picker-provided handles can be temporary.
• Geolocation.GetLastKnownLocationAsync can be stale. Use GetLocationAsync with a GeolocationRequest for current location.
• Choose GeolocationRequest.DesiredAccuracy deliberately. Use medium or low accuracy to conserve battery unless the feature truly requires GPS precision.
• Pass cancellation tokens to location requests where the UI can cancel or the page can disappear.
• Migrating apps should audit old Xamarin READ_EXTERNAL_STORAGE declarations because Android 13+ media permissions changed runtime behavior.

Permission UX

• Ask at the moment of need, not on first launch.
• Explain the user benefit before invoking the platform prompt.
• Provide a useful fallback when access is denied.
• Make denied/blocked states visible and announced with SemanticProperties.Description, SemanticScreenReader.Announce, or a focused explanatory label.
• Avoid loops that immediately re-request permission after denial.
• Make error/cancelled states visible and testable with AutomationId when UI is affected.

Validation Checklist

• Platform manifests/plists include only the declarations required by the feature.
• Runtime permission requests happen before capability APIs that require them.
• Denied and cancelled flows are handled without crashes.
• Denied permission UI is visible, accessible, and offers Settings when the platform requires manual re-enable.
• Picked files/media are copied when durable access is required.
• Location code handles stale last-known data, timeout, and cancellation.