main.dart

Widget _getListViewWidget() {
    // We want the ListView to have the flexibility to expand to fill the
    // available space in the vertical axis
    return new Flexible(
        child: new ListView.builder(
            // The number of items to show
            itemCount: _currencies.length,
            // Callback that should return ListView children
            // The index parameter = 0...(itemCount-1)
            itemBuilder: (context, index) {
              // Get the currency at this position
              final Map currency = _currencies[index];

              // Get the icon color. Since x mod y, will always be less than y,
              // this will be within bounds
              final MaterialColor color = _colors[index % _colors.length];

              return _getListItemWidget(currency, color);
            }));
  }