Flutter 常用的特殊组件

1、Cupertino

Cupertino -- iOS风格的组件

引用：import 'package:flutter/cupertino.dart';

文档：https://flutter.cn/docs/development/ui/widgets/cupertino

 

Material -- 安卓风格的组件

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

import 'package:flutter/cupertino.dart';
import 'package:flutter/material.dart';
import 'dart:io';

class Home extends StatelessWidget {
  const Home({Key? key}) : super(key: key);

  @override
  Widget build(BuildContext context) {
    Widget dialogBox = Container();
    // 判断当前的平台信息
    // iOS
    if (Platform.isIOS) {
      dialogBox = const CupertinoDialog();
    }
    // Android
    if (Platform.isAndroid) {
      dialogBox = const MaterialDialog();
    }
    return Scaffold(
      appBar: AppBar(
        title: const Text('Dialog'),
      ),
      body: dialogBox,
    );
  }
}

// 安卓风格的弹窗
class MaterialDialog extends StatelessWidget {
  const MaterialDialog({Key? key}) : super(key: key);

  @override
  Widget build(BuildContext context) {
    return Container(
      padding: const EdgeInsets.symmetric(horizontal: 10),
      child: AlertDialog(
        title: const Text('提示'),
        content: const Text('确认删除吗？'),
        actions: [
          TextButton(onPressed: () {}, child: const Text('取消')),
          TextButton(onPressed: () {}, child: const Text('确认')),
        ],
      ),
    );
  }
}

// iOS风格的弹窗
class CupertinoDialog extends StatelessWidget {
  const CupertinoDialog({Key? key}) : super(key: key);

  @override
  Widget build(BuildContext context) {
    return Container(
      padding: const EdgeInsets.symmetric(horizontal: 10),
      child: CupertinoAlertDialog(
        title: const Text('提示'),
        content: const Text('确认删除吗？'),
        actions: [
          CupertinoDialogAction(
            child: const Text('取消'),
            onPressed: () {},
          ),
          CupertinoDialogAction(
            child: const Text('确认'),
            onPressed: () {},
          ),
        ],
      ),
    );
  }
}

2、SafeArea

该组件会为其子组件插入足够的内边距以避免操作系统的影响，例如：iPhone X 的刘海屏

文档：https://api.flutter-io.cn/flutter/widgets/SafeArea-class.html

 

 

3、dio

dio是一个强大的Dart Http请求库，支持Restful API、FormData、拦截器、请求取消、Cookie管理、文件上传/下载、超时、自定义适配器等...

pub地址：https://pub.dev/packages/dio

中文文档：https://github.com/flutterchina/dio/blob/master/README-ZH.md

安装：flutter pub add dio

引入：import 'package:dio/dio.dart';

// ignore_for_file: avoid_print
import 'package:flutter/material.dart';
import 'package:dio/dio.dart';

class Home extends StatelessWidget {
  const Home({Key? key}) : super(key: key);

  // 异步获取图片
  void getPic() async {
    try {
      var response =
          await Dio().get('https://dog.ceo/api/breed/hound/images/random');
      print(response);
      print(response.data);
      print(response.data['message']);
      print(response.data['status']);
    } catch (e) {
      print(e);
    }
  }

  @override
  Widget build(BuildContext context) {
    return Scaffold(
      appBar: AppBar(
        title: const Text('dio'),
      ),
      body: Container(
         double.infinity,
        padding: const EdgeInsets.all(10),
        child: ElevatedButton(
          // 点击事件，调用 HTTP 请求
          onPressed: getPic,
          child: const Text('点击发送请求'),
        ),
      ),
    );
  }
}

4、flutter_swiper

Flutter 中最好的轮播组件，支持多种布局、无限滚动，可同时兼容 Android 和 iOS

文档：https://pub.flutter-io.cn/packages/flutter_swiper

安装：flutter pub add flutter_swiper

使用：import 'package:flutter_swiper/flutter_swiper.dart';

基本属性：

scrollDirection：默认值 Axis.horizontal，轮播的方向

loop：默认值 true，取值为 false 时，禁止无限滚动

index：默认值 0，初始的下标

autoplay：默认值 false，取值为 true 时，启动自动轮播

duration：默认值 3000ms，每次动画（轮播切换）耗时

分页器 Pagination 属性：

继承自 SwiperPlugin，为 Swiper 提供了额外的 UI，通过 new SwiperPagination() 来创建 pagination

alignment：默认值 Alignment.bottomCenter，分页器的位置

margin：默认值 EdgeInsets.all(10.0)，与父容器的间距

builder：默认值 SwiperPagination.dots，两种不同的样式 SwiperPagination.dots 和 SwiperPagination.fraction

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

class Home extends StatelessWidget {
  const Home({
    Key? key,
    this.imgs = const [
      'assets/image1.jpg',
      'assets/image2.jpg',
      'assets/image3.jpg'
    ],
  }) : super(key: key);

  final List<String> imgs;

  @override
  Widget build(BuildContext context) {
    return Scaffold(
      appBar: AppBar(
        title: const Text('轮播图'),
      ),
      body: ListView(
        children: [
          const Text(
            '轮播图基本用法：',
            style: TextStyle(
              fontSize: 32,
            ),
            textAlign: TextAlign.left,
          ),
          Container(
            padding: const EdgeInsets.symmetric(horizontal: 10),
            height: 150,
            child: Swiper(
              autoplay: true,
              itemCount: imgs.length,
              itemBuilder: (context, index) {
                return Image.asset(
                  imgs[index],
                  fit: BoxFit.cover,
                );
              },
              // 默认的分页器（轮播图的指示点）
              pagination: const SwiperPagination(),
              // 默认的控制器（左右箭头导航）
              control: const SwiperControl(),
            ),
          ),
          const Text(
            '轮播图3D效果：',
            style: TextStyle(
              fontSize: 32,
            ),
            textAlign: TextAlign.left,
          ),
          Container(
            padding: const EdgeInsets.symmetric(horizontal: 10),
            height: 150,
            child: Swiper(
              autoplay: true,
              itemCount: imgs.length,
              itemBuilder: (context, index) {
                return Image.asset(
                  imgs[index],
                  fit: BoxFit.cover,
                );
              },
              // 主轮播图的缩放比例，默认是1
              viewportFraction: 0.7,
              // 非主轮播图的缩放比例
              scale: 0.7,
            ),
          ),
          const Text(
            '轮播图布局：',
            style: TextStyle(
              fontSize: 32,
            ),
            textAlign: TextAlign.left,
          ),
          Container(
            padding: const EdgeInsets.symmetric(horizontal: 10),
            height: 150,
            child: Swiper(
              autoplay: true,
              itemCount: imgs.length,
              itemBuilder: (context, index) {
                return Image.asset(
                  imgs[index],
                  fit: BoxFit.cover,
                );
              },
              itemWidth: 300,
              // 当 layout 取值为 TINDER 时，必须指明高度，否则会报错
              // itemHeight: 150,
              // layout: SwiperLayout.TINDER,
              layout: SwiperLayout.STACK,
            ),
          ),
        ],
      ),
    );
  }
}

 5、shared_preferences

是一个异步的本地数据缓存库，支持的数据类型有：int, double, bool, String, List<String>

文档：https://pub.flutter-io.cn/packages/shared_preferences

安装：flutter pub add shared_preferences

引用：import 'package:shared_preferences/shared_preferences.dart';

使用：SharedPreferences prefs = await SharedPreferences.getInstance();

增/改：setString(key, value)

查：getString(key)

删：remove(key), clear()

 

// ignore_for_file: avoid_print
import 'package:flutter/material.dart';
import 'package:shared_preferences/shared_preferences.dart';

class Home extends StatelessWidget {
  const Home({Key? key}) : super(key: key);

  @override
  Widget build(BuildContext context) {
    return Scaffold(
      appBar: AppBar(
        title: const Text('shared_preferences'),
      ),
      body: Container(
         double.infinity,
        padding: const EdgeInsets.all(10),
        child: Column(
          mainAxisAlignment: MainAxisAlignment.spaceAround,
          crossAxisAlignment: CrossAxisAlignment.center,
          children: [
            ElevatedButton(
              onPressed: _incrementCounter,
              child: const Text('递增'),
            ),
            ElevatedButton(
              onPressed: _decrementCounter,
              child: const Text('递减'),
            ),
            ElevatedButton(
              onPressed: _removeCounter,
              child: const Text('删除'),
            ),
            ElevatedButton(
              onPressed: _addStr,
              child: const Text('缓存字符串'),
              style: ButtonStyle(
                backgroundColor: MaterialStateProperty.all(Colors.pink),
              ),
            ),
            ElevatedButton(
              onPressed: _getStr,
              child: const Text('读取字符串'),
              style: ButtonStyle(
                backgroundColor: MaterialStateProperty.all(Colors.pink),
              ),
            ),
            ElevatedButton(
              onPressed: _clearPrefs,
              child: const Text('清空'),
              style: ButtonStyle(
                backgroundColor: MaterialStateProperty.all(Colors.pink),
              ),
            ),
          ],
        ),
      ),
    );
  }

  // 递增
  _incrementCounter() async {
    // 获取保存实例
    SharedPreferences prefs = await SharedPreferences.getInstance();
    // 需要注意运算的优先级 + 先于 ?? 执行
    int counter = (prefs.getInt('counter') ?? 0) + 1;
    print('Pressed $counter times.');
    await prefs.setInt('counter', counter);
  }

  // 递减
  _decrementCounter() async {
    // 获取保存实例
    SharedPreferences prefs = await SharedPreferences.getInstance();
    int counter = prefs.getInt('counter') ?? 0;
    if (counter > 0) {
      counter--;
    }
    print('Pressed $counter times.');
    await prefs.setInt('counter', counter);
  }

  // 删除
  _removeCounter() async {
    SharedPreferences prefs = await SharedPreferences.getInstance();
    await prefs.remove('counter');
  }

  // 缓存字符串
  _addStr() async {
    SharedPreferences prefs = await SharedPreferences.getInstance();
    await prefs.setString('msg', 'Hello World !');
  }

  // 读取缓存
  _getStr() async {
    SharedPreferences prefs = await SharedPreferences.getInstance();
    String msg = prefs.getString('msg') ?? '';
    print('缓存的字符串内容是：$msg');
  }

  // 清空所有缓存内容
  _clearPrefs() async {
    SharedPreferences prefs = await SharedPreferences.getInstance();
    prefs.clear();
  }
}