14Flutter StatefulWidget有状态组件、页面上绑定数据、改变页面数据、实现计数器功能、动态列表

/**
 * Flutter StatefulWidget有状态组件、页面上绑定数据、改变页面数据
 * 在Flutter中自定义组件其实就是一个类，这个类需要继承StatelessWidget/StatefulWidget
 * StatelessWidget是无状态组件，状态不可变得widget
 * StatefulWidget是有状态组件，持有的状态可能在widget生命周期改变。如果我们想
 * 改变页面中的数据化的这个时候就需要用到StatefulWidget
*/

import 'package:flutter/material.dart';

void main() {
  runApp(MyApp());
}
class MyApp extends StatelessWidget {
  @override
  Widget build(BuildContext context) {
    // TODO: implement build
    return MaterialApp(
      home: Scaffold(
        appBar: AppBar(
          title: Text('自定义组件'),
        ),
        body: HomeContent(),
      ),
    );
  }
}

class HomeContent extends StatelessWidget {
  @override
  Widget build(BuildContext context) {
    //Stack结合align实现布局：
    return HomePage();
  }
}

//自定义有状态组件：
class HomePage extends StatefulWidget {
  HomePage({Key key}) : super(key: key);

  _HomePageState createState() => _HomePageState();
}

class _HomePageState extends State<HomePage> {
  int countNum=0;
  @override
  Widget build(BuildContext context) {
    return Column(
      children: <Widget>[
        SizedBox(height: 200),
        Chip(label: Text('${this.countNum}')),
        SizedBox(height: 20),
        RaisedButton(
          child: Text('按钮'),
          onPressed: (){
            setState(() { //只有有状态的组件里面才有
              this.countNum++;
            });
          },
        )
      ],
    );
  }
}

demo2

main.dart

import 'package:flutter/material.dart';
void main() {
  runApp(MyApp());
}
class MyApp extends StatelessWidget {
  @override
  Widget build(BuildContext context) {
    // TODO: implement build
    return MaterialApp(
      home: Scaffold(
        appBar: AppBar(
          title: Text('自定义组件'),
        ),
        body: HomeContent(),
      ),
    );
  }
}

class HomeContent extends StatelessWidget {
  @override
  Widget build(BuildContext context) {
    //Stack结合align实现布局：
    return HomePage();
  }
}

//自定义有状态组件：
class HomePage extends StatefulWidget {
  HomePage({Key key}) : super(key: key);

  _HomePageState createState() => _HomePageState();
}

class _HomePageState extends State<HomePage> {
  List list=new List();
  @override
  Widget build(BuildContext context) {
    return ListView(
      children: <Widget>[
        Column(
          children:this.list.map((value){
            return ListTile(
              title: Text(value),
            );
          }).toList()
        ),
        RaisedButton(
          child: Text('按钮'),
          onPressed: (){
            setState(() {
              this.list.add('新增数据1');
              this.list.add('新增数据2');
            });
          },
        )
      ],
    );
  }
}