Locking Orientation in Flutter

To set the orientation to portrait in Flutter, add the following code inside your void main() function:

void main() async {
  WidgetsFlutterBinding.ensureInitialized();
  await SystemChrome.setPreferredOrientations([
    DeviceOrientation.portraitUp,
    DeviceOrientation.portraitDown,
  ]);
  runApp(MyApp());
}

However, this code will only take effect after the native splash screen is displayed. If your app launches in landscape mode, the splash screen will appear in landscape before switching to portrait, which can cause issues with responsive libraries like flutter_screenutil. This is because the library might calculate the screen size based on the landscape orientation initially.

For example:

ScreenUtilInit(
  designSize: const Size(360, 690),
  builder: () => MyApp(),
);

To ensure that the orientation is locked from the start, you need to configure the native code as well.

Locking Orientation on Android

To lock the orientation to portrait mode on Android, modify the AndroidManifest.xml file. Add the android:screenOrientation="portrait" attribute to the activity tag for your main activity:

<activity
    android:name=".MainActivity"
    android:screenOrientation="portrait"
    ... >
    ...
</activity>

Locking Orientation on iOS

For iOS, you need to adjust the Info.plist file to restrict the orientations. Add the following keys and values to support only portrait orientation:

<key>UISupportedInterfaceOrientations</key>
<array>
    <string>UIInterfaceOrientationPortrait</string>
    <string>UIInterfaceOrientationPortraitUpsideDown</string>
</array>
<key>UISupportedInterfaceOrientations~ipad</key>
<array>
    <string>UIInterfaceOrientationPortrait</string>
    <string>UIInterfaceOrientationPortraitUpsideDown</string>
    <string>UIInterfaceOrientationLandscapeLeft</string>
    <string>UIInterfaceOrientationLandscapeRight</string>
</array>

Note: iPad applications must support both portrait and landscape orientations. If you are planning to release your app for iPads, ensure that your design accommodates both orientations.