Add ability to customize NavigationBar indicator overlay and fix indicator shape for the overlay (#138901)
fixes [Provide ability to override `NavigationBar` indicator ink response overlay](https://github.com/flutter/flutter/issues/138850)
fixes [`NavigationBar.indicatorShape` is ignored, `NavigationBarThemeData.indicatorShape` is applied to the indicator inkwell](https://github.com/flutter/flutter/issues/138900)
### Code sample
<details>
<summary>expand to view the code sample</summary>
```dart
import 'package:flutter/material.dart';
void main() => runApp(const MyApp());
class MyApp extends StatelessWidget {
const MyApp({super.key});
@override
Widget build(BuildContext context) {
return const MaterialApp(
debugShowCheckedModeBanner: false,
home: Scaffold(
bottomNavigationBar: NavigationBarExample(),
),
);
}
}
class NavigationBarExample extends StatefulWidget {
const NavigationBarExample({super.key});
@override
State<NavigationBarExample> createState() => _NavigationBarExampleState();
}
class _NavigationBarExampleState extends State<NavigationBarExample> {
int index = 0;
@override
Widget build(BuildContext context) {
return NavigationBar(
elevation: 0,
overlayColor: const MaterialStatePropertyAll<Color>(Colors.transparent),
// indicatorShape: RoundedRectangleBorder(
// borderRadius: BorderRadius.circular(4.0),
// ),
indicatorColor: Colors.transparent,
selectedIndex: index,
onDestinationSelected: (int index) {
setState(() {
this.index = index;
});
},
destinations: const <Widget>[
NavigationDestination(
selectedIcon: Icon(Icons.home_filled),
icon: Icon(Icons.home_outlined),
label: 'Home',
),
NavigationDestination(
selectedIcon: Icon(Icons.favorite),
icon: Icon(Icons.favorite_outline),
label: 'Favorites',
),
],
);
}
}
```
</details>
### Before
#### Cannot override `NavigationBar` Indicator ink well overlay
#### Indicator shape is ignored for the indicator overlay
### After
#### Can use `NavigationBar.overlayColor` or `NavigationBarThemeData.NavigationBar` to override default indicator overlay
`overlayColor: MaterialStatePropertyAll<Color>(Colors.red.withOpacity(0.33)),`
`overlayColor: MaterialStatePropertyAll<Color>(Colors.transparent),`
#### Indicator shape is respected for the indicator overlay
397fd25be1