无法定义“const”构造函数，因为字段“currentUser”是用非常量值初始化的

Question

• 无法定义“const”构造函数，因为字段“currentUser” 用一个非常量值初始化。
• 无法为具有非最终字段的类定义 const 构造函数。
• 参数类型 'Stream>>' 不能 分配给参数类型'Widget Function(BuildContext, AsyncSnapshot>)'。
• 已指定命名参数“builder”的参数。
• 正文可能正常完成，导致返回“null”，但 返回类型可能是不可为空的类型。

如何解决这个错误。感谢您对此的帮助。

people.dart

import 'package:cloud_firestore/cloud_firestore.dart';
import 'package:flutter/cupertino.dart';
import 'package:flutter/material.dart';
import 'package:firebase_auth/firebase_auth.dart';


class People extends StatelessWidget {
  const People({Key? key}) : super(key: key);
  var currentUser = FirebaseAuth.instance.currentUser!.uid;

  void callChatScreen(String name, String uid){

  }

  @override
  Widget build(BuildContext context) {
    return StreamBuilder<QuerySnapshot>(
        builder: FirebaseFirestore.instance
            .collection("users")
        .where('uid',isNotEqualTo: currentUser)
            .snapshots(),
              builder:(BuildContext,AsyncSnapshot<QuerySnapshot>snapshot){
          if(snapshot.hasError){
            return Center(
              child: Text("Something went wrong"),
            );
          }


          if (snapshot.connectionState == ConnectionState.waiting) {
            return Center(
              child: Text("Loading"),
            );
          }

          if (snapshot.hasData) {
            return CustomScrollView(
              slivers: [
                CupertinoSliverNavigationBar(
                  largeTitle: Text("People"),
                ),
                SliverList(
                    delegate: SliverChildListDelegate(
                        snapshot.data!.docs.map((DocumentSnapshot document) {
                          Map<String, dynamic>? data = document.data() as Map<String, dynamic>?;

                          return CupertinoListTile(
                            onTap:()=> callChatScreen(data['name'],data['uid'])
                            title: Text(data!['name']),
                            subtitle: Text(data['status']),
                          );

                        }).toList()))
              ],
            );
          }
          //return Container();
              });
      }
  }

Answer 1

试试这个：

class People extends StatelessWidget {
   People({Key? key}) : super(key: key);
  var currentUser = FirebaseAuth.instance.currentUser!.uid;

  void callChatScreen(String name, String uid){

  }

  @override
  Widget build(BuildContext context) {
    return StreamBuilder<QuerySnapshot>(
        stream: FirebaseFirestore.instance
            .collection("users")
        .where('uid',isNotEqualTo: currentUser)
            .snapshots(),
              builder:(BuildContext,AsyncSnapshot<QuerySnapshot>snapshot){
          if(snapshot.hasError){
            return Center(
              child: Text("Something went wrong"),
            );
          }


          if (snapshot.connectionState == ConnectionState.waiting) {
            return Center(
              child: Text("Loading"),
            );
          }

          if (snapshot.hasData) {
            return CustomScrollView(
              slivers: [
                CupertinoSliverNavigationBar(
                  largeTitle: Text("People"),
                ),
                SliverList(
                    delegate: SliverChildListDelegate(
                        snapshot.data!.docs.map((DocumentSnapshot document) {
                          Map<String, dynamic>? data = document.data() as Map<String, dynamic>?;

                          return CupertinoListTile(
                            onTap:()=> callChatScreen(data['name'],data['uid'])
                            title: Text(data!['name']),
                            subtitle: Text(data['status']),
                          );

                        }).toList()))
              ],
            );
          }
          //return Container();
              });
      }
  }