小编Ven*_*noM的帖子

我对 Flutter 相当陌生，我要在 Flutter 上构建 Messenger Chap 应用程序，但我面临“LateInitilization：字段 'searchSnapShot' 尚未初始化”的问题。以下是导致该问题的代码片段：

Widget searchList() {
return searchSnapShot != null ? ListView.builder(
  itemCount: searchSnapShot.docs.length,
    shrinkWrap: true,
    itemBuilder: (context, index) {
      return SearchTile(
          userName: searchSnapShot.docs[index].data()["name"],
          userEmail: searchSnapShot.docs[index].data()["email"],
      );
    }
) : Container();
}

此代码片段的作用是返回与搜索查询匹配的用户列表。以下是整个search.dart的代码：

    import 'package:chat_app/services/database.dart';
import 'package:chat_app/widgets/widgets.dart';
import 'package:cloud_firestore/cloud_firestore.dart';
import 'package:flutter/material.dart';

class SearchScreen extends StatefulWidget {

  @override
  _SearchScreenState createState() => _SearchScreenState();
}

class _SearchScreenState extends State<SearchScreen> {

  DatabaseMethods databaseMethods = new DatabaseMethods();
  TextEditingController searchTextEditingController = new TextEditingController();

  late QuerySnapshot <Map<String, dynamic>> …

所以我正在尝试使用 update() 函数来更新选定的用户，但是当我单击提交时，它只会返回索引（应该如此）但不更新任何内容。以下是我的代码：

StudentController（资源控制器）：

 <?php

namespace App\Http\Controllers;

use Illuminate\Http\Request;

use App\Student;

class StudentController extends Controller
{
    /**
     * Display a listing of the resource.
     *
     * @return \Illuminate\Http\Response
     */
    public function index()
    {
        $students = Student::all();
        return view ('main',compact('students'));
    }
/**
 * Show the form for creating a new resource.
 *
 * @return \Illuminate\Http\Response
 */
public function create()
{
    return view ('create');
}

/**
 * Store a newly created resource in storage.
 *
 * @param  \Illuminate\Http\Request  $request
 * @return …

这是我当前的主屏幕，我试图将关闭按钮放置在每个容器的右上角，这最终会删除这些聊天室，而我在弄清楚如何做到这一点时遇到了一些麻烦。图片下方是我的代码。

child: Container(
    decoration: BoxDecoration(
        color: Color(0xff240046),
      borderRadius: BorderRadius.circular(15)
    ),
    padding: EdgeInsets.symmetric(horizontal: 12, vertical: 18),
    margin: EdgeInsets.symmetric(vertical: 8),
    child: Row(
      children: [
        ClipRRect(
          borderRadius: BorderRadius.circular(30),
          child: profilePicUrl.isNotEmpty ? Image.network(
            profilePicUrl,
            height: 40,
            width: 40,
          ) : null,
        ),
        SizedBox(width: 12),
        Column(
          crossAxisAlignment: CrossAxisAlignment.start,
          children: [
            Text(
              name,
              style: TextStyle(
                  color: Color(0xff7b2cbf),
                  fontSize: 16),
            ),
            SizedBox(height: 3),
            Text(widget.lastMessage,
            style: TextStyle(
              color: Color(0xffd4d4d4),
            ),)
          ],
        ),
        Column(
          children: [
            Align(
              alignment: Alignment.topRight,
              child: Icon(
                  Icons.close,

              ),
            )
          ],
        ),

      ],
    ),
  ), …