Permissions

Web content permission flow has two layers:

1. The app must have the operating system permission.
2. The WebView must approve the web page request.

WebViewController(onPermissionRequest: ...) or setOnPlatformPermissionRequest handles the WebView layer.

final controller = WebViewController(
  onPermissionRequest: (WebViewPermissionRequest request) async {
    if (request.types.contains(WebViewPermissionResourceType.camera)) {
      await request.grant();
    } else {
      await request.deny();
    }
  },
);

Call grant() or deny() once. Platform request objects ignore duplicate decisions where possible.

Common Resource Types

Type	Meaning
WebViewPermissionResourceType.camera	Camera capture.
WebViewPermissionResourceType.microphone	Audio capture.

Platform-Specific Resource Types

Platform	Type	Meaning
Android	AndroidWebViewPermissionResourceType.midiSysex	MIDI sysex access.
Android	AndroidWebViewPermissionResourceType.protectedMediaId	Protected media identifier.

Geolocation

final android = controller.platform as AndroidWebViewController;

await android.setGeolocationPermissionsPromptCallbacks(
  onShowPrompt: (GeolocationPermissionsRequestParams request) async {
    return const GeolocationPermissionsResponse(
      allow: true,
      retain: false,
    );
  },
  onHidePrompt: () {
    debugPrint('Geolocation prompt hidden');
  },
);

  onShowPrompt: (request) async {
    return const GeolocationPermissionsResponse(
      allow: true,
      retain: false,
    );
  },
);

Geolocation generally requires secure origins (https) in modern engines.

File Selector

<input type="file"> works without a Dart callback:

Platform	Behavior
Android	Built-in Photo Picker for image/video, ACTION_GET_CONTENT for other MIME types, camera when capture is set.
iOS	WKWebView system picker (PHPicker / document picker).
macOS	WKUIDelegate.runOpenPanel presents NSOpenPanel.
Windows / Linux / Web	Engine or browser dialog. Engine-owned; no common Dart callback.

Cancel, permission denial, and errors complete the native callback with null so the input can be used again.

Android Photo Picker and SAF do not need READ_MEDIA_* or READ_EXTERNAL_STORAGE. Camera capture requests CAMERA at runtime. Declare CAMERA in the host AndroidManifest.xml. iOS pages that use capture or a photo library picker need NSCameraUsageDescription and usually NSPhotoLibraryUsageDescription in Info.plist. Missing usage strings can crash the app.

Optional Android override:

await (controller.platform as AndroidWebViewController)
    .setOnShowFileSelector((FileSelectorParams params) async {
  debugPrint('accept=${params.acceptTypes}');
  return <String>['content://media/picker/0'];
});

Return an empty list to cancel. FileSelectorParams includes:

Field	Meaning
isCaptureEnabled	The page prefers live capture such as camera or microphone.
acceptTypes	MIME types accepted by the page.
filenameHint	Suggested filename when the mode allows saving.
mode	open, openMultiple, or save.

Add READ_MEDIA_IMAGES / READ_MEDIA_VIDEO (API 33+) or READ_EXTERNAL_STORAGE (API 32 and below) only if this custom callback reads the MediaStore directly.

Fullscreen Custom Widgets

await (controller.platform as AndroidWebViewController)
    .setCustomWidgetCallbacks(
  onShowCustomWidget: (Widget widget, VoidCallback onHidden) {
    Navigator.of(context).push(
      MaterialPageRoute<void>(
        fullscreenDialog: true,
        builder: (_) => widget,
      ),
    );
  },
  onHideCustomWidget: () {
    Navigator.of(context).pop();
  },
);

Web Permissions

The web implementation can mediate navigator.mediaDevices.getUserMedia for same-origin content and plugin-managed isolated HTML by wrapping the page API. It can report camera and microphone requests to onPermissionRequest.

The browser still owns the final permission prompt. request.grant() only allows the page call to continue to the browser permission layer.