I know there should be a neater way to code this than manually adding the class getKey() for every single iteration. However, whenever I run this code, I get all black rectangles. How do I go about getting the colors I input within the getKey() function? It's suppose to look like a xylophone on the phone at execution.

```
import 'package:audioplayers/audio_cache.dart';
import 'package:flutter/cupertino.dart';
import 'package:flutter/material.dart';

void main() => runApp(XylophoneApp());

class XylophoneApp extends StatelessWidget {
  // void playSound() {
  //   final player = AudioCache();
  //   player.play('note$n.wav');
  // }

  Expanded buildKey({int n, backgroundColors: Color}) {
    return Expanded(
      child: FloatingActionButton(
        onPressed: () {
          final player = AudioCache();
          player.play('note$n.wav');
        },
        shape: RoundedRectangleBorder(),
      ),
    );
  }

  @override
  Widget build(BuildContext context) {
    return MaterialApp(
      home: Scaffold(
        backgroundColor: Colors.black,
        body: SafeArea(
          child: Column(
              crossAxisAlignment: CrossAxisAlignment.stretch,
              children: <Widget>[
                buildKey(n: 1, backgroundColors: Colors.red),
                buildKey(n: 2, backgroundColors: Colors.orange),
                buildKey(n: 3, backgroundColors: Colors.yellow),
                buildKey(n: 4, backgroundColors: Colors.green),
                buildKey(n: 5, backgroundColors: Colors.teal),
                buildKey(n: 6, backgroundColors: Colors.blue),
                buildKey(n: 7, backgroundColors: Colors.purple),
              ]),
        ),
      ),
    );
  }
}

```