Create app_tracking_transparency.md

flutter_documentation/app_tracking_transparency.md

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+---
+title: App Tracking Transparency
+layout: home
+parent: Flutter
+nav_order: 4
+---
+
+Starting iOS 14+, it is necessary to ask user for permission to track their data, which is necessary for better ads targeting. In case user refuses to be tracked, IDFA is set to zeroes. More about App Tracking Transparency can be read [here]. </br>
+One of the ways to ask for user's permission is to use App Tracking Transparency [plugin], made specifically for this purpose.
+
+## Info.plist
+The first step is adding these lines to your Info.plist file (the same one where Google Ad Manager app ID was added) to display a tracking authorization request when user downloads your app and opens it for the first time. Inside the `<string>` tags add the text you want to display in the request.
+```xml
+<key>NSUserTrackingUsageDescription</key>
+<string>We use your data for advertising purposes to improve our services.</string>
+```
+
+## pubspec.yaml
+In your `pubspec.yaml` file dependencies include this dependency:
+```yaml
+app_tracking_transparency: ^2.0.4
+```
+## Plugin's implementation
+
+In your dart code, add this code in order for a request popup to be visible. Note: for the request popup to appear, it is necessary to display additional dialog using 'showCustomTrackingDialog' method. More about this can be read in [plugin]'s description.
+```dart
+import 'package:app_tracking_transparency/app_tracking_transparency.dart';
+
+//...
+
+class _MyAppState extends State<MyAppState> {
+  String _authStatus = 'Unknown';
+
+  @override
+  void initState() {
+    super.initState();
+
+    WidgetsFlutterBinding.ensureInitialized()
+        .addPostFrameCallback((_) => initPlugin());
+  }
+
+  Future<void> showCustomTrackingDialog(BuildContext context) async =>
+      await showDialog<void>(
+        context: context,
+        builder: (context) =>
+            AlertDialog(
+              title: const Text('Permission to track data'),
+              content: const Text(
+                "Text, explaining in more detail on why your app needs to permission to track user's data."
+              ),
+              actions: [
+                TextButton(
+                  onPressed: () => Navigator.pop(context),
+                  child: const Text('Continue'),
+                ),
+              ],
+            ),
+      );
+
+  Future<void> initPlugin() async {
+    final TrackingStatus status = await AppTrackingTransparency
+        .trackingAuthorizationStatus;
+    if (status == TrackingStatus.notDetermined) {
+      await showCustomTrackingDialog(context);
+      await Future.delayed(const Duration(milliseconds: 200));
+      await AppTrackingTransparency.requestTrackingAuthorization();
+      setState(() => _authStatus = '$status');
+    }
+  }
+  //The rest of your code
+}
+```
+
+----
+[here]: https://developer.apple.com/documentation/apptrackingtransparency
+[plugin]: https://pub.dev/packages/app_tracking_transparency