Question

我的Flutter应用程序出现问题，我有一个仅返回StreamBuilder的类，它运行良好，可以显示Cloud Firestore中的数据。但是，当我尝试将此类包装在Column或ListView类中时，它什么也没显示。

我需要它来显示当前页面的名称。而且AppBar类已经带有应用程序名称，所以我也不能使用它。

有人知道我该如何包装它并使它继续运行吗？

示例代码有效

  class NewCardsList extends StatelessWidget {

  @override
  Widget build(BuildContext context) {
    return new StreamBuilder<QuerySnapshot>(
      stream: firestore.collection('cards_list').snapshots(),
      builder: (BuildContext context, AsyncSnapshot<QuerySnapshot> snapshot) {
        if (!snapshot.hasData) return const Text('Connecting...');
        final int cardLength = snapshot.data.documents.length;
        return new ListView.builder(
          itemCount: cardLength,
          itemBuilder: (int index) {
            final DocumentSnapshot _card= snapshot.data.documents[index];
            return new ListTile(
              title: new Text(_card['title']),
              subtitle: new Text(_card['description']),
            );
          },
        );
      },
    );
  }
}

示例代码不起作用

class NewCardsList extends StatelessWidget {

      @override
      Widget build(BuildContext context) {
        return new Column(
          children: <Widget> [
            Text("Your Card List"),
            StreamBuilder<QuerySnapshot>(
          stream: firestore.collection('cards_list').snapshots(),
          builder: (BuildContext context, AsyncSnapshot<QuerySnapshot> snapshot) {
            if (!snapshot.hasData) return const Text('Connecting...');
            final int cardLength = snapshot.data.documents.length;
            return new ListView.builder(
              itemCount: cardLength,
              itemBuilder: (int index) {
                final DocumentSnapshot _card= snapshot.data.documents[index];
                return new ListTile(
                  title: new Text(_card['title']),
                  subtitle: new Text(_card['description']),
                );
              },
            );
          },
        ]));
      }
    }

Answer 1

使用Flexible（）包装Streambuilder，然后使用Column（）包装Flexible，将column设置为scaffold（）的主体

Answer 2

此外，您只需在shrinkWrap: true内创建属性ListView.builder()。

 return new ListView.builder(
          shrinkWrap: true,
          itemCount: cardLength,
          itemBuilder: (int index) {
            final DocumentSnapshot _card= snapshot.data.documents[index];
            return new ListTile(
              title: new Text(_card['title']),
              subtitle: new Text(_card['description']),
            );

如何在Flutter中使用Column或ListView类包装StreamBuilder类？

2 个答案: