在ch!上使用bang !操作

data.state.length <= 0
          ? child!
          : ListView.builder(
              itemBuilder: (context, index) => Container(),
              itemCount: 4,
            );

使用以下相同样品溶液;

body: Consumer<GreatPlaces>(
    child: const Center(
      child: Text('Got no places yet, start adding some!'),
    ),
    builder: (ctx, greatPlaces, ch) => greatPlaces.items.isEmpty
        ? ch!
        : ListView.builder(
            itemBuilder: (ctx, index) => ListTile(
              leading: CircleAvatar(
                backgroundImage: FileImage(
                  greatPlaces.items[index].image,
                ),
              ),
              title: Text(greatPlaces.items[index].title),
              onTap: () {},
            ),
            itemCount: greatPlaces.items.length,
          ),
  ),

请尝试以下代码：

Consumer<GreatPlaces>(
  child: Center(
    child: const Text(
      'Got no places yet, start adding some',
    ),
  ),
  builder: (ctx, greatPlaces, ch) => greatPlaces.items.length <= 0
      ? ch ?? Container() // You change Container to other widget
      : ListView.builder(
          itemBuilder: (ctx, index) => Center(),
          itemCount: 5,
        ),
),