在 flutter 中显示过滤后的数据。答案

【问题标题】：show filtered data in. stream builder in flutter在 flutter 中显示过滤后的数据。
【发布时间】：2022-11-23 11:18:06
【问题描述】：

学习目的我创建了一个显示基于事务列表的 firebase 数据的屏幕。这里我添加了三个文本按钮来过滤数据，例如

All : 显示所有记录收入：仅显示收入交易费用：仅显示费用交易。

这是否意味着我必须制定 3 种未来的方法？但是如果我有很多过滤条件怎么办……还有其他方法吗……此外，我将根据每年的周月过滤日期……

class _HomeScreen2State extends State<HomeScreen2> {
  Stream _getAllEntries() {
    return FirebaseFirestore.instance
        .collection('users')
        .doc(widget.loggeduser.userid)
        .collection('expenses')
        .orderBy("date", descending: true)
        .snapshots();
  }

  @override
  Widget build(BuildContext context) {
    var size = MediaQuery.of(context).size;

    return Scaffold(
      appBar: showAppbar(),
      body: SafeArea(
          child: Column(
        children: [
          Padding(
            padding: EdgeInsets.all(10),
            child: Align(
              alignment: Alignment.centerLeft,
              child: Row(
                mainAxisSize: MainAxisSize.min,
                mainAxisAlignment: MainAxisAlignment.spaceBetween,
                children: [
                  TextButton(onPressed: () {}, child: Text('All')),
                  TextButton(onPressed: () {}, child: Text('Expenses')),
                  TextButton(onPressed: () {}, child: Text('Income')),
                ],
              ),
            ),
          ),
          SizedBox(
            height: 10,
          ),
          showTransactions(size),
        ],
      )),
      floatingActionButton: buildfloatingactionbutton(),
    );
  }

  Widget showTransactions(Size size) {
    return Container(
      height: size.height * .65,
      // color: Colors.red,
      child: StreamBuilder(
          stream: _getAllEntries(),
          builder: (context, snapshot) {
            if (snapshot.connectionState == ConnectionState.active) {
              if (snapshot.hasData) {
                QuerySnapshot querysnapshot = snapshot.data as QuerySnapshot;
                if (querysnapshot.docs.length > 0) {
                  return ListView.builder(
                      padding: EdgeInsets.symmetric(vertical: 10),
                      itemCount: querysnapshot.docs.length,
                      itemBuilder: (context, index) {
                        final trans = TransactionModel.fromjson(
                            querysnapshot.docs[index].data()
                                as Map<String, dynamic>);
                        return TransactionCard(
                          ontap: () async {},
                          amount: trans.amount.toStringAsFixed(2),
                          datetime: trans.date.toString(),
                          paymentby: trans.paymentmode,
                          category: trans.category.title,
                          categoryicon: trans.category.iconurl,
                          isexpense: trans.isexpense,
                        );
                      }); //listview end
                } else {
                  return Container(
                      child: Center(child: Text('No Transaction Found...')));
                }
              } else {
                if (snapshot.hasError) {
                  return Text('error found');
                } else {
                  return Text('empty..');
                }
              }
            } else {
              return Center(child: CircularProgressIndicator());
            }
          }),
    );
  }

【问题讨论】：

标签： flutter

【解决方案1】：

添加一个新变量，告诉 flutter 你的过滤器

String myFilter = "all"; // *** or 'Expenses' or 'Income'

然后在流定义中使用该新变量：

  Stream _getAllEntries(String myFilter ) {
    return FirebaseFirestore.instance
        .collection('users')
        .doc(widget.loggeduser.userid)
        .collection(myFilter) //*** see change... or use a filter ***
        .orderBy("date", descending: true)
        .snapshots();
  }

然后在 3 个按钮中的每一个中更新过滤器的值：

TextButton(onPressed: () {
  setState(() {
    myFilter = "all";
  });
}, child: Text('All')),

最后，更新对流的调用：

child: StreamBuilder(
          stream: _getAllEntries(myFilter),

【讨论】：