flutter - ScreenUtil.instance = ScreenUtil(宽度:750，高度:1334，allowFontScaling:true);为什么给我错误？

Question

在youtube上观看了有关设计应用程序登录页面的视频后，我逐行复制了代码，但是这两行login.dart给我一个错误。这两条线是什么意思？

ScreenUtil.instance = ScreenUtil.getInstance()..init(context);
ScreenUtil.instance = ScreenUtil(width: 750, height: 1334, allowFontScaling: true);

这是login.dart页面代码

import 'package:flutter/material.dart';
import 'package:flutter_screenutil/flutter_screenutil.dart';


class LoginPage extends StatefulWidget {
  @override
  _LoginPageState createState() => _LoginPageState();
}

class _LoginPageState extends State<LoginPage> {

  @override
  Widget build(BuildContext context) {
    ScreenUtil.instance = ScreenUtil.getInstance()..init(context);
    ScreenUtil.instance =
        ScreenUtil(width: 750, height: 1334, allowFontScaling: true);
    return Scaffold(
      backgroundColor: Colors.white,
      resizeToAvoidBottomPadding: true,
      body: Stack(
        fit: StackFit.expand,
        children: <Widget>[
          Column(
            crossAxisAlignment: CrossAxisAlignment.end,
            children: <Widget>[
              Padding(
                padding: EdgeInsets.only(top: 50.0, right: 20.0),
                child: Image.asset("assets/login_logo.png"),
              ),
              Expanded(
                child: Container(),
              ),
              Image.asset("assets/image_02.png")
            ],
          ),
          SingleChildScrollView(
            child: Padding(
              padding: EdgeInsets.fromLTRB(28.0, 50.0, 28.0, 0.0),
              child: Column(
                children: <Widget>[
                  Row(
                    children: <Widget>[
                      Image.asset("assets/logo.png")
                    ],
                  ),
                ],
              ),
            ),
          ),
        ],
      ),
    );
  }
}

我在pubspec.yaml文件中添加了屏幕实用程序打包 flutter_screenutil:^ 1.0.2

Answer 1

在此视频中，使用了flutter_screenutil的旧版本:0.7.0。
您正在使用1.0.2和API has been changed in 1.0.0 。

因此，代替:

ScreenUtil.instance = ScreenUtil.getInstance()..init(context);
ScreenUtil.instance = ScreenUtil(width: 750, height: 1334, allowFontScaling: true);

您应该使用:

ScreenUtil.init(context, width: 750, height: 1334, allowFontScaling: true);

并且，而不是:

ScreenUtil.getInstance().setWidth(...); // or .setHeight(...)

您应该使用:

ScreenUtil().setWidth(...); // or .setHeight(...);