Flutter基础 -- Flutter布局练习（小项目）

目录

1. Splash 布局（第一页）

1.1 目标

1.2 当前效果图

1.3 创建 Splash 界面

1.4 设置 MaterialApp

1.5 设置 Splash 背景色

1.6 布局 Splash 界面

1.7 总结

2. Splash 圆角图片

2.1 目标

2.2 当前效果图

2.3 蓝湖下载图片

2.4 图片导入项目

2.5 编写 assets 索引

2.6 编写标志 Logo

2.7 总结

3. Splash 文字

3.1 目标

3.2 当前效果图

3.3 蓝湖标注查看

3.4 字体下载导入

3.5 编写 TextStyle

3.6 加入间距

3.7 总结

4. Splash 倒计时

4.1 目标

4.2 当前效果图

4.3 改成有状态组件

4.4 实现倒计时

4.5 重构文字显示函数

4.6 完整代码

4.7 总结

1. Welcome 图片尺寸适应（第二页）

1.1 目标

1.2 当前效果图

1.3 设置全局字体

1.4 界面布局、标题

1.5 图片尺寸适应

1.6 总结

2. Welcome 导航切换

2.1 目标

2.2 当前效果图

2.3 底部按钮

2.4 导航切换

2.5 总结

1. login 布局（第三页）

1.1 目标

1.2 布局

1.3 总结

2. login 登录表单

2.1 目标

2.2 当前效果图

2.3 登录表单

2.4 总结

3. login 按钮抽取

3.1 目标

3.2 当前效果图

3.3 按钮组件抽取

3.4 登录按钮

3.5 欢迎按钮

3.6 总结

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1. Splash 布局（第一页）

1.1 目标

• 查看蓝湖标注
• 初始项目
• 创建 splash 界面

github 目标图片在里面

https://github.com/ducafecat/flutter_quickstart_learn

1.2 当前效果图

1.3 创建 Splash 界面

lib/pages/splash.dart

import 'package:flutter/material.dart';import '../common/index.dart';class SplashPage extends StatelessWidget {const SplashPage({Key? key}) : super(key: key);// 主视图Widget _buildView(BuildContext context) {return Text("splash");}@overrideWidget build(BuildContext context) {return Scaffold(body: Center(child: _buildView(context)),);}
}

1.4 设置 MaterialApp

lib/main.dart

import 'package:flutter/material.dart';import 'pages/splash.dart';void main() {runApp(const MyApp());
}class MyApp extends StatelessWidget {const MyApp({Key? key}) : super(key: key);@overrideWidget build(BuildContext context) {return MaterialApp(title: 'Flutter Quick Start',// 首页home: const SplashPage(),// 关闭 debug 标签debugShowCheckedModeBanner: false,);}
}

1.5 设置 Splash 背景色

lib/common/app_colors.dart

import 'package:flutter/material.dart';/// 颜色配置
class AppColors {/// splash 背景色static const Color backgroundSplash = Color(0xff0274bc);
}

lib/pages/splash.dart

import '../common/index.dart';...@overrideWidget build(BuildContext context) {return Scaffold(backgroundColor: AppColors.backgroundSplash, // 背景色body: _buildView(context),);}

1.6 布局 Splash 界面

lib/pages/splash.dart

  // 主视图Widget _buildView(BuildContext context) {return Column(mainAxisAlignment: MainAxisAlignment.center,crossAxisAlignment: CrossAxisAlignment.center,children: [// 图标Container(color: Colors.white,width: 120,height: 120,),// 标题const Text("Online Market"),// 倒计时const Text("10"),],);}

1.7 总结

• 蓝湖标注平台 布局、尺寸、字体、颜色...

• 初始项目 pages common 目录创建

• 配置 MaterialApp.home 首页

• 配置 Scaffold 脚手架背景色

• 全局颜色管理 AppColors

• 布局 Splash 界面

2. Splash 圆角图片

2.1 目标

• 导入图片资源
• 使用层叠布局编写 logo

2.2 当前效果图

2.3 蓝湖下载图片

依次选中图片，选中 PNG 格式，IOS 类型，3X 高清，最后下载当前切图        

2.4 图片导入项目

放入你的项目 assets/images/3.0x/logo.pn

生成 1x 2x 图片

插件地址 Flutter GetX Generator - 猫哥 - Visual Studio Marketplace

修改 pubspec.yaml

flutter:...assets:- assets/images/

2.5 编写 assets 索引

编写 lib/common/assets.dart， 将 assets/images/files.txt 内容复制进去，这个文件是插件生成的，防止文件太多，手写出错

/// 图片资源
class AssetsImages {static const logoPng = 'assets/images/logo.png';
}

2.6 编写标志 Logo

lib/pages/splash.dart

  // 图标Widget _buildLogo() {return Stack(alignment: Alignment.center,children: [// 底部Container(width: 120,height: 120,decoration: BoxDecoration(color: Colors.white,borderRadius: BorderRadius.circular(120 / 2),),),// 图标Image.asset(AssetsImages.logoPng,width: 84,height: 80,),],);}

  // 主视图Widget _buildView(BuildContext context) {return Column(mainAxisAlignment: MainAxisAlignment.center,crossAxisAlignment: CrossAxisAlignment.center,children: [// 图标_buildLogo(),// 标题const Text("Online Market"),// 倒计时const Text("10"),],);}

2.7 总结

• 下载蓝湖切图 选择 png 格式 ios 模式 3x 尺寸
• 使用猫哥插件生成 1x 2x 图片，创建资源索引管理
• 使用层叠布局创建 logo
• 使用函数进一步的管理代码

3. Splash 文字

3.1 目标

• 导入字体文件
• 配置文字样式

3.2 当前效果图

3.3 蓝湖标注查看

需要关注的属性有：

• font-size 字体大小
• font-family 字体名称
• font-weight 字体重度
• color 颜色
• line-height 行高

3.4 字体下载导入

google 字体下载

https://fonts.google.com/

下载后导入 assets/fonts/

编辑 pubspec.yaml

  fonts:- family: Poppinsfonts:- asset: assets/fonts/Poppins-Light.ttfweight: 300- asset: assets/fonts/Poppins-Regular.ttfweight: 400- asset: assets/fonts/Poppins-Medium.ttfweight: 500- asset: assets/fonts/Poppins-Bold.ttfweight: 700

3.5 编写 TextStyle

lib/pages/splash.dart

  // 标题const Text("Online Market",style: TextStyle(fontSize: 19,fontFamily: "Poppins",fontWeight: FontWeight.bold,color: Colors.white,height: 22 / 19,),),

fontFamily 中写入字体名称 Poppins

height 文本跨度的行高将为 [fontSize] 的倍数并且正好是 fontSize *height 逻辑像素 高。换行的时候才有意义

3.6 加入间距

标题和图标间距 24，和计数器 27

lib/pages/splash.dart

  // 主视图Widget _buildView(BuildContext context) {return Column(mainAxisAlignment: MainAxisAlignment.center,crossAxisAlignment: CrossAxisAlignment.center,children: [// 图标_buildLogo(),const SizedBox(height: 24),// 标题const Text("Online Market",style: TextStyle(fontSize: 19,fontFamily: "Poppins",fontWeight: FontWeight.bold,color: Colors.white,height: 22 / 19,),),const SizedBox(height: 27),// 倒计时const Text("10",style: TextStyle(fontSize: 19,fontFamily: "Poppins",fontWeight: FontWeight.bold,color: Colors.white,height: 22 / 19,),),],);}

3.7 总结

• 导入字体 pubspec 中详细明确 字体名称、 字体文件、字体weight
• 用不到的字体文件不用方式 assets/fonts 目录中
• 设置文字样式 fontSize、fontFamily、fontWeight、color
• 具体值的间距用 SizedBox 来配置

4. Splash 倒计时

4.1 目标

• 使用有状态组件
• 倒计时更新组件

4.2 当前效果图

4.3 改成有状态组件

lib/pages/splash.dart

import 'package:flutter/foundation.dart';
import 'package:flutter/material.dart';import '../common/index.dart';class SplashPage extends StatefulWidget {const SplashPage({Key? key}) : super(key: key);@overrideState<SplashPage> createState() => _SplashPageState();
}class _SplashPageState extends State<SplashPage> {// 图标Widget _buildLogo() {return Stack(alignment: Alignment.center,children: [// 底部Container(width: 120,height: 120,decoration: BoxDecoration(color: Colors.white,borderRadius: BorderRadius.circular(120 / 2),),),// 图标Image.asset(AssetsImages.logoPng,width: 84,height: 80,),],);}// 主视图Widget _buildView(BuildContext context) {return Column(mainAxisAlignment: MainAxisAlignment.center,crossAxisAlignment: CrossAxisAlignment.center,children: [// 图标_buildLogo(),const SizedBox(height: 24),// 标题const Text("Online Market",style: TextStyle(fontSize: 19,fontFamily: "Poppins",fontWeight: FontWeight.bold,color: Colors.white,height: 22 / 19,),),const SizedBox(height: 27),// 倒计时Text("0",style: const TextStyle(fontSize: 19,fontFamily: "Poppins",fontWeight: FontWeight.bold,color: Colors.white,height: 22 / 19,),),],);}@overrideWidget build(BuildContext context) {return Scaffold(backgroundColor: AppColors.backgroundSplash,body: Center(child: _buildView(context)),);}
}

4.4 实现倒计时

lib/pages/splash.dart

计数 num

  // 计数 numfinal duration = 10;int number = 0;

倒计时函数

  // 倒计时Future<void> _countdown() async {number = duration;for (int i = 0; i < duration; i++) {await Future.delayed(const Duration(seconds: 1), () {if(mounted == ture) {setState(() {number--;});}});// 倒计时结束, 进入 welcomeif (number == 0) {if (kDebugMode) {print("倒计时结束");}}}}

注意 await async 异步函数的语法

初始执行

  @overridevoid initState() {super.initState();_countdown();}

打印显示

  // 主视图Widget _buildView(BuildContext context) {...// 倒计时Text(number > 0 ? "$number" : "done",style: const TextStyle(fontSize: 19,fontFamily: "Poppins",fontWeight: FontWeight.bold,color: Colors.white,height: 22 / 19,),),

4.5 重构文字显示函数

macos 下是 option + enter , 也可以在组件上 右键 -> 重构...

文字显示函数

  // 文字显示Text _buildText(String text) {return Text(text,style: const TextStyle(fontSize: 19,fontFamily: "Poppins",fontWeight: FontWeight.bold,color: Colors.white,height: 22 / 19,),);}

主视图代码

  // 主视图Widget _buildView(BuildContext context) {return Center(child: Column(mainAxisAlignment: MainAxisAlignment.center,children: [// logo_buildLogo(),const SizedBox(height: 24),// 标题_buildText("Online Market"),const SizedBox(height: 27),// 计数器_buildText("10"),// end],),);}

4.6 完整代码

lib/pages/splash.dart

import 'package:flutter/material.dart';import '../common/app_colors.dart';
import '../common/assets.dart';class SplashPage extends StatefulWidget {const SplashPage({Key? key}) : super(key: key);@overrideState<SplashPage> createState() => _SplashPageState();
}class _SplashPageState extends State<SplashPage> {// 计数变量final duration = 3;int number = 0;// 倒计时函数Future<void> _countdown() async {number = duration;for (var i = 0; i < duration; i++) {await Future.delayed(const Duration(seconds: 1), () {if (mounted == true) {setState(() {number--;});}});if (number == 0) {print("倒计时结束");}}}@overridevoid initState() {super.initState();_countdown();}// logoWidget _buildLogo() {return Stack(alignment: Alignment.center,children: [// 底部Container(width: 120,height: 120,decoration: BoxDecoration(color: Colors.white,borderRadius: BorderRadius.circular(120 / 2),),),// 图片Image.asset(AssetsImages.logoPng,width: 84,height: 80,),],);}// 文字显示Text _buildText(String text) {return Text(text,style: const TextStyle(fontSize: 19,fontFamily: "Poppins",fontWeight: FontWeight.bold,color: Colors.white,height: 22 / 19,),);}// 主视图Widget _buildView(BuildContext context) {return Center(child: Column(mainAxisAlignment: MainAxisAlignment.center,children: [// logo_buildLogo(),const SizedBox(height: 24),// 标题_buildText("Online Market"),const SizedBox(height: 27),// 计数器_buildText(number > 0 ? "$number" : "done"),// end],),);}@overrideWidget build(BuildContext context) {return Scaffold(backgroundColor: AppColors.backgroundSplash,body: _buildView(context),);}
}

4.7 总结

• 无状态组件重构成有状态组件
• 使用 Future.delayed 方式实现倒计时
• 使用 三目运算符 控制显示

1. Welcome 图片尺寸适应（第二页）

1.1 目标

• 全局配置样式、字体
• 图片适配高宽
• 布局代码练习

1.2 当前效果图

 

1.3 设置全局字体

lib/main.dart

class MyApp extends StatelessWidget {const MyApp({Key? key}) : super(key: key);@overrideWidget build(BuildContext context) {return MaterialApp(...// 样式theme: ThemeData(primarySwatch: Colors.orange,fontFamily: "Poppins", // 字体),

字体全局放在 theme fontFamily 属性中

1.4 界面布局、标题

lib/pages/welcome.dart

import 'package:flutter/material.dart';/// 欢迎页面
class WelcomePage extends StatelessWidget {const WelcomePage({Key? key}) : super(key: key);// 主视图Widget _buildView() {return Column(mainAxisAlignment: MainAxisAlignment.center,children: [// 标题const Padding(padding: EdgeInsets.symmetric(horizontal: 30),child: Text("Browse & Order All Products at Any Time",textAlign: TextAlign.center,style: TextStyle(fontSize: 20,fontFamily: "Poppins",fontWeight: FontWeight.bold,color: Color(0xff2B2A2A),height: 23 / 20,),),),// 图Container(),// 底部按钮Container(),],);}@overrideWidget build(BuildContext context) {return Scaffold(body: _buildView(),);}
}

标题代码抽取函数，整理代码

  // 标题Padding _buildTitle() {return const Padding(padding: EdgeInsets.symmetric(horizontal: 30),child: Text("Browse & Order All Products at Any Time",textAlign: TextAlign.center,style: TextStyle(fontSize: 20,fontFamily: "Poppins",fontWeight: FontWeight.bold,color: Color(0xff2B2A2A),height: 23 / 20,),),);}

  // 主视图Widget _buildView() {return Column(children: [const SizedBox(height: 100),// 标题_buildTitle(),...

1.5 图片尺寸适应

从蓝湖下载图片导入项目，这里不再重复叙述

lib/pages/welcome.dart

  // 图片Image _buildImage() {return Image.asset(AssetsImages.welcomePng,height: 300,width: double.infinity,fit: BoxFit.none,//fit:BoxFit.fitWidth);}

  // 主视图Widget _buildView() {return Column(mainAxisAlignment: MainAxisAlignment.center,children: [// 标题_buildTitle(),const SizedBox(height: 70),// 图_buildImage(),// 底部按钮_buildBtns(),],);}

1.6 总结

• 通过 ThemeData.fontFamily 设置全局字体
• padding: EdgeInsets.symmetric(horizontal: 30) 水平 Padding 距离
• 图片组件 Image.fit 设置宽高适配
• 布局第一规则 从上往下

2. Welcome 导航切换

2.1 目标

• 布局规则 “从上往下、从左往右”
• 全局按钮颜色样式
• 布局训练 横向、纵向 混合

2.2 当前效果图

2.3 底部按钮

lib/pages/welcome.dart

  // goto 登录页面void onLogin(BuildContext context) {}// 底部按钮Padding _buildBtns(BuildContext context) {return Padding(padding: const EdgeInsets.symmetric(horizontal: 24),child: Row(children: [// skipTextButton(onPressed: () => onLogin(context),child: const Text("Skip",style: TextStyle(fontSize: 15,fontWeight: FontWeight.w300,color: Color(0xff2B2A2A),),),),// 撑开const Expanded(child: SizedBox(),),// Get StartedContainer(height: 42,width: 140,clipBehavior: Clip.antiAlias,decoration: const BoxDecoration(borderRadius: BorderRadius.all(Radius.circular(18),),),child: ElevatedButton(onPressed: () => onLogin(context),style: ButtonStyle(elevation: MaterialStateProperty.all(0),minimumSize: MaterialStateProperty.all(Size.zero),),child: const Text("Get Started",style: TextStyle(fontSize: 16,fontWeight: FontWeight.w300,color: Colors.white,),),),),],),);}

  // 主视图Widget _buildView(BuildContext context) {return Column(mainAxisAlignment: MainAxisAlignment.center,children: [// 标题_buildTitle(),const SizedBox(height: 70),// 图_buildImage(),const SizedBox(height: 70),// 底部按钮_buildBtns(context),],);}

2.4 导航切换

splash 倒计时结束进入 welcome 界面

  // 倒计时Future<void> _countdown() async {number = duration;for (int i = 0; i < duration; i++) {...// 倒计时结束, 进入 welcomeif (number == 0) {Navigator.pushReplacement(context,MaterialPageRoute(builder: (context) => const WelcomePage()));}}}

2.5 总结

设计稿布局分析 “从上往下、从左往右”
先写布局代码结构
注意命名 _buildXXX 开头都是私有布局函数
导航 Navigator.pushReplacement 进入新界面并替换当前

1. login 布局（第三页）

1.1 目标

看标注布局界面（千锤百炼就会了）

1.2 布局

lib/pages/login.dart

  // 登录表单Widget _buildForm() {return Container();}

	// 主视图Widget _buildView() {return Container(padding: const EdgeInsets.symmetric(horizontal: 15),color: AppColors.backgroundSplash,child: Column(mainAxisAlignment: MainAxisAlignment.center,children: [// 图标Image.asset(AssetsImages.logoPng,width: 60,),const SizedBox(height: 20),// 主标const Text("Let’s Sign You In",style: TextStyle(fontSize: 20,color: Colors.white,fontWeight: FontWeight.bold,),),const SizedBox(height: 10),// 子标const Text("Welcome back, you’ve been missed!",style: TextStyle(fontSize: 13,color: Colors.white,fontWeight: FontWeight.w300,),),const SizedBox(height: 50),// 表单_buildForm(),],),);}

  @overrideWidget build(BuildContext context) {return Scaffold(body: _buildView(),);}

1.3 总结

• 记住布局规则 “从上往下、从左往右”
• 用函数拆分视图结构

2. login 登录表单

2.1 目标

• 编写表单
• 有效性检查

2.2 当前效果图

2.3 登录表单

lib/pages/login.dart

  // 账号输入是否有效bool isUserNameValid = false;

  // 登录表单Widget _buildForm() {return Container(padding: const EdgeInsets.fromLTRB(20, 50, 20, 20),decoration: BoxDecoration(color: Colors.white,borderRadius: BorderRadius.circular(35),),child: Column(crossAxisAlignment: CrossAxisAlignment.start,children: [// Username or E-Mailconst Text("Username or E-Mail",style: TextStyle(fontSize: 15,color: Color(0xff838383),fontWeight: FontWeight.w300,),),TextField(onChanged: (value) {bool valid = false;if (value.length >= 6) {valid = true;} else {valid = false;}setState(() {isUserNameValid = valid;});},decoration: InputDecoration(hintText: "@",// labelText: "Username or E-Mail",// labelStyle: const TextStyle(//   fontSize: 15,//   color: Color(0xff838383),//   fontWeight: FontWeight.w300,// ),prefixIcon: Image.asset(AssetsImages.iconUserPng,width: 23,height: 23,),suffixIcon: isUserNameValid == true? const Icon(Icons.done,color: Colors.green,): null,),),// 间距const SizedBox(height: 35),// Passwordconst Text("Password",style: TextStyle(fontSize: 15,color: Color(0xff838383),fontWeight: FontWeight.w300,),),TextField(obscureText: true,decoration: InputDecoration(hintText: "6 digits",// labelText: "Password",// labelStyle: const TextStyle(//   fontSize: 15,//   color: Color(0xff838383),//   fontWeight: FontWeight.w300,// ),prefixIcon: Image.asset(AssetsImages.iconLockPng,width: 23,height: 23,),suffixIcon: TextButton(onPressed: () {},child: const Text("Forget?",style: TextStyle(fontSize: 15,color: Color(0xff0274bc),fontWeight: FontWeight.w500,),),),),),// 间距const SizedBox(height: 30),// Sign In// 间距const SizedBox(height: 16),// Don’t have an account?  + Sign UpRow(mainAxisAlignment: MainAxisAlignment.center,children: [// 文字const Text("Don’t have an account? ",style: TextStyle(fontSize: 15,color: Color(0xff171717),fontWeight: FontWeight.w300,),),// 按钮TextButton(onPressed: () {},child: const Text("Sign Up",style: TextStyle(fontSize: 15,color: Color(0xff0274bc),fontWeight: FontWeight.bold,),),),],),],),);}

2.4 总结

• 通过 TextField.decoration 属性进行装饰
• TextField.obscureText 开启密码

3. login 按钮抽取

3.1 目标

• 抽取公共按钮组件
• 修改成纯 ElevatedButton 按钮

3.2 当前效果图

3.3 按钮组件抽取

lib/common/widgets.dart

import 'package:flutter/material.dart';/// 按钮组件
class ButtonWidget extends StatelessWidget {const ButtonWidget({Key? key,this.height,this.widget,this.radius,this.onPressed,this.text,}) : super(key: key);/// 文字final String? text;/// 高度final double? height;/// 宽度final double? widget;/// 圆角final double? radius;/// 点击事件final void Function()? onPressed;@overrideWidget build(BuildContext context) {return ElevatedButton(onPressed: onPressed,style: ButtonStyle(// 阴影高度elevation: MaterialStateProperty.all(0),// 最小尺寸minimumSize: MaterialStateProperty.all(Size(widget ?? double.infinity, height ?? double.infinity)),// 形状 圆角shape: MaterialStateProperty.all(RoundedRectangleBorder(borderRadius: BorderRadius.all(Radius.circular(radius ?? 18),),),),),child: Text(// 文字text ?? "",// 文字样式style: const TextStyle(fontSize: 16,fontWeight: FontWeight.w300,color: Colors.white,),),);}
}

3.4 登录按钮

lib/pages/login.dart

  // 登录表单Widget _buildForm() {...// Sign InButtonWidget(text: 'Sign In',onPressed: () {},height: 60,widget: double.infinity,radius: 18,),

3.5 欢迎按钮

lib/pages/welcome.dart

  // 底部按钮Padding _buildBtns(BuildContext context) {...// Get StartedButtonWidget(text: "Get Started",height: 42,widget: 140,radius: 32,onPressed: () => onLogin(context),),

  // goto 登录页面void onLogin(BuildContext context) {Navigator.push(context,MaterialPageRoute(builder: (context) => const LoginPage()),);}

3.6 总结

• 公共组件类抽取方法
• ElevatedButton 组件属性配置

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