【重要】带你了解Dart泛型在Flutter中的应用-辅导说明和源码

Question

main.dart

import 'package:flutter/material.dart';
import 'package:flutter_dart_learn/data_type.dart';
import 'package:flutter_dart_learn/generic_learn.dart';
import 'package:flutter_dart_learn/oop_learn.dart';

import 'function_learn.dart';

void main() => runApp(MyApp());

class MyApp extends StatelessWidget {
  @override
  Widget build(BuildContext context) {
    return MaterialApp(
      title: 'Flutter必备Dart基础',
      theme: ThemeData(
        primarySwatch: Colors.blue,
      ),
      home: MyHomePage(title: 'Flutter必备Dart基础'),
    );
  }
}

class MyHomePage extends StatefulWidget {
  MyHomePage({Key key, this.title}) : super(key: key);

  final String title;

  @override
  _MyHomePageState createState() => _MyHomePageState();
}

class _MyHomePageState extends State<MyHomePage> {
  @override
  Widget build(BuildContext context) {
//    _oopLearn();
//    _functionLearn();
    _genericLearn();
    return Scaffold(
      appBar: AppBar(
        title: Text(widget.title),
      ),
      body: Center(
        child: ListView(
          children: <Widget>[
//            DataType(),
          ],
        ),
      ),
    );
  }

  void _oopLearn() {
    //创建Student的对象
    Student stu1 = Student('清华', 'Jack', 18);
    stu1.school = '985';
    print(stu1.toString());
    Student stu2 = Student('北大', 'Tom', 16, city: '上海', country: '中国');
    print(stu2.toString());

    Student.doPrint('_oopLearn');

    StudyFlutter sf = StudyFlutter();
    sf.study();
    Logger log1 = Logger();
    Logger log2 = Logger();
    print(log1 == log2);
  }

  void _functionLearn() {
    TestFunction testFunction = TestFunction();
    testFunction.start();
  }

  void _genericLearn() {
    TestGeneric testGeneric = TestGeneric();
    testGeneric.start();
  }
}

generic_learn.dart

//入口方法
//构造方法
//实例方法
//setters 和 getters
//静态方法
//抽象方法
//私有方法
//匿名方法
//泛型方法

import 'package:flutter_dart_learn/oop_learn.dart';

class TestGeneric {

  void start() {
    //泛型
    Cache<String> cache1 = Cache();
    cache1.setItem('cache1', 'cache1'); //泛型作用：类型检查约束类比：List<String>
    String string1 = cache1.getItem('cache1');
    print(string1);

    Cache<int> cache2 = Cache();
    cache2.setItem('cache2', 1008);
    int int1 = cache2.getItem('cache2');
    print(int1);

    Member<Student> member = Member(Student('', '', 16));
    print(member.fixedName());
  }
}

///泛型：
///通俗理解：泛型主要是解决类、接口、方法的复用性、以及对不特定数据类型的支持

///泛型类
///泛型作用：提高代码服用度
class Cache<T> {
  static final Map<String, Object> _cached = Map();

  void setItem(String key, T value) {
    _cached[key] = value;
  }

  ///泛型方法
  T getItem(String key) {
    return _cached[key];
  }
}

///有时候你在实现类似通用接口的泛型中，期望的类型是某些特定类型时，这时可以使用类型约束
class Member<T extends Person> {
  T _person;

  ///泛型作用：约束参数类型
  Member(this._person);

  String fixedName() {
    return 'fixed:${_person.name}';
  }
}

Answer 1

提问者 CrazyCodeBoy 2019-08-01 20:16:49

以上。