Flutter 如何在列表視圖中顯示來自 firebase 的列表

Question

我在StreamBuilder小部件中從 firebase 獲取列表。 我想在ListView小部件中顯示它，但它不起作用。

這是我的代碼：

final current = document.data as Map<String, dynamic>;
final activities = current["activities"] as List;
List titles = activities.map((e) => e["title"]).toList();
List av = activities.map((e) => e["days"]).toList();

ListView.builder(
  shrinkWrap: true,
  itemCount: av.elementAt(i).length,
  itemBuilder: (context, index) {
    return ListTile(
      title: Text(av.elementAt(i)[0][index]),
    );
  },
),

我究竟做錯了什么？

Answer 1

諸如此類的所有變量

final current = document.data as Map<String, dynamic>;
final activities = current["activities"] as List;
List titles = activities.map((e) => e["title"]).toList();
List av = activities.map((e) => e["days"]).toList();

一旦收到來自 firestore 的數據，就需要加載。
因此，以下是您的代碼：

 StreamBuilder(
            stream: _firestoreStream, //use .snapshot() to get data
            builder: (context, snapshot) {
              if (snapshot.hasData) {
                final current = snapshot.data as Map<String, dynamic>;
                final activities = current["activities"] as List;
                List titles = activities.map((e) => e["title"]).toList();
                List av = activities.map((e) => e["days"]).toList();

                return ListView.builder(
                  shrinkWrap: true,
                  itemCount: av.elementAt(i).length,
                  itemBuilder: (context, index) {
                    return ListTile(
                      title: Text(av.elementAt(i)[0][index]),
                    );
                  },
                );
              } else {
                return const CircularProgressIndicator();
              }
            }),