提示：
（抱歉有错误。英语不是我的母语）
（我是新来的）
我的颤振项目中有很多错误。我认为这是因为包裹。当我写: 时import 'package:flutter/material.dart';，android studio 在它下面画了一条红线，表示错误，当我在导入包上按住鼠标指针时，它说：Target of URI doesn't exist: 'package:flutter/material.dart'我认为这就是所有错误的原因。我该如何解决？
我的错误：
error: Target of URI doesn't exist: 'package:flutter/material.dart'. (uri_does_not_exist at [untitled6] bin\main.dart:1)
error: The function 'runApp' isn't defined. (undefined_function at [untitled6] bin\main.dart:3)
error: Classes can only extend other classes. (extends_non_class at [untitled6] bin\main.dart:5)
error: Undefined class 'Widget'. (undefined_class at [untitled6] bin\main.dart:8)
error: Undefined class 'BuildContext'. (undefined_class at [untitled6] bin\main.dart:8)
error: The method 'MaterialApp' isn't defined for the type 'MyApp'. (undefined_method at [untitled6] bin\main.dart:9)
error: Classes can only extend other classes. (extends_non_class at [untitled6] bin\main.dart:16)
error: Undefined class 'Widget'. (undefined_class at [untitled6] bin\main.dart:19)
error: Undefined class 'BuildContext'. (undefined_class at [untitled6] bin\main.dart:19)
error: The method 'Material' isn't defined for the type 'MyScaffold'. (undefined_method at [untitled6] bin\main.dart:20)
error: The method 'Column' isn't defined for the type 'MyScaffold'. (undefined_method at [untitled6] bin\main.dart:21)
error: The name 'Widget' isn't a type so it can't be used as a type argument. (non_type_as_type_argument at [untitled6] bin\main.dart:22)
error: The name 'Row' isn't a class. (creation_with_non_type at [untitled6] bin\main.dart:23)
error: The name 'IconButton' isn't a class. (creation_with_non_type at [untitled6] bin\main.dart:24)
error: The method 'Icon' isn't defined for the type 'MyScaffold'. (undefined_method at [untitled6] bin\main.dart:25)
error: Undefined name 'Icons'. (undefined_identifier at [untitled6] bin\main.dart:25)
error: The name 'Text' isn't a class. (creation_with_non_type at [untitled6] bin\main.dart:29)
error: The name 'IconButton' isn't a class. (creation_with_non_type at [untitled6] bin\main.dart:30)
error: The method 'Icon' isn't defined for the type 'MyScaffold'. (undefined_method at [untitled6] bin\main.dart:32)
error: Undefined name 'Icons'. (undefined_identifier at [untitled6] bin\main.dart:32)
error: Expected to find ')'. (expected_token at [untitled6] bin\main.dart:37)
error: Expected to find ']'. (expected_token at [untitled6] bin\main.dart:38)
error: Expected to find ')'. (expected_token at [untitled6] bin\main.dart:38)
error: Expected to find ')'. (expected_token at [untitled6] bin\main.dart:39)
info: The method doesn't override an inherited method. (override_on_non_overriding_member at [untitled6] bin\main.dart:8)
info: Unnecessary new keyword. (unnecessary_new at [untitled6] bin\main.dart:11)
info: The method doesn't override an inherited method. (override_on_non_overriding_member at [untitled6] bin\main.dart:19)
info: Unnecessary new keyword. (unnecessary_new at [untitled6] bin\main.dart:23)
info: Unnecessary new keyword. (unnecessary_new at [untitled6] bin\main.dart:24)
info: Unnecessary new keyword. (unnecessary_new at [untitled6] bin\main.dart:29)
info: Unnecessary new keyword. (unnecessary_new at [untitled6] bin\main.dart:30)
请你帮助我好吗？我的工作延迟了几天