I used as to import the flutter project in github and ran it, and found that it could not be run: import 'package:flutter/material.dart'; the red wavy line below

I used as to import the flutter project in github and ran it. I found that it could not run: import 'package:flutter/material.dart'; the red wavy line below, take a look first main.dart, as shown below:

I tried it but it didn't work. I went to Baidu to find a lot. Or not

But I asked the QQ group and someone told me, as shown below:

What do you think is wrong?

What I think is, if you have a solution, you can comment on me .AS环境不一样，最好的方式，就是你现在创建一个项目，自己去加代码，而不是直接拿代码去运行，你解决不了这种情况