Fix Flutter 'PlatformException(channel-error, Unable to establish connection)'

A PlatformException means a Dart method channel call reached the native boundary and something went wrong on the other side — the channel isn't registered, the platform method threw, or the plugin isn't built into the binary.

Fix 1: Rebuild After Adding Native Code

flutter clean && flutter pub get
cd ios && pod install && cd ..
flutter run    # full rebuild registers the channel

Fix 2: Always Catch PlatformException

try {
  final result = await platform.invokeMethod('getBatteryLevel');
} on PlatformException catch (e) {
  debugPrint('Native call failed: ${e.code} ${e.message}');
  // show a graceful fallback to the user
}

Fix 3: Check Platform Availability

If you call a channel that only exists on Android while running on iOS (or web), it errors. Guard with Platform.isAndroid/kIsWeb before invoking platform-specific methods.