Flutter中显示数据时为何得到Instance of Future<List<int>>？

问题出在characteristic46?.read()是异步方法，返回的是Future<List>类型，直接字符串插值会输出对象实例的描述字符串，必须等待异步操作完成拿到实际数据后再显示，以下是两种可行方案：

方案一：先获取异步结果再弹出对话框 #

将addPostFrameCallback的回调改为async，先await获取read()的结果，再传入Text组件：

WidgetsBinding.instance.addPostFrameCallback((timeStamp) async {
  final result = await characteristic46?.read();
  showDialog(
    context: context,
    barrierColor: Colors.transparent,
    builder: (context) {
      return AlertDialog(
        title: Text('Be Careful ${result ?? 'No data'}'),
        backgroundColor: Color.fromARGB(45, 231, 148, 54),
        alignment: Alignment.topCenter,
      );
    });
});

方案二：用FutureBuilder在对话框内处理异步结果 #

如果需要在对话框显示时等待异步结果，可以用FutureBuilder包裹Text，根据异步状态显示对应内容：

WidgetsBinding.instance.addPostFrameCallback((timeStamp) {
  showDialog(
    context: context,
    barrierColor: Colors.transparent,
    builder: (context) {
      return AlertDialog(
        title: FutureBuilder<List<int>>(
          future: characteristic46?.read(),
          builder: (context, snapshot) {
            if (snapshot.connectionState == ConnectionState.done) {
              return Text('Be Careful ${snapshot.data ?? 'No data'}');
            } else {
              // 异步加载中，可替换为自定义加载组件
              return CircularProgressIndicator();
            }
          },
        ),
        backgroundColor: Color.fromARGB(45, 231, 148, 54),
        alignment: Alignment.topCenter,
      );
    });
});

内容的提问来源于stack exchange，提问作者rania