Flutter中文网

---

日志随笔

一、复习

• Scrollbar添加通知NotificationListener监听后，应该return false;如果返回的是true，那么Scrollbar会消失

二、功能型组件

1、导航返回拦截

iOS应该不需要

2、数据共享（InheritedWidget）

InheritedWidget提供了一种数据在widget树中从上到下传递、共享的方式，比如我们在应用的根widget中通过InheritedWidget共享了一个数据，那么我们便可以在任意子widget中来获取该共享的数据

InheritedWidget和React中的context功能类似，和逐级传递数据相比，它们能实现组件跨级传递数据

import 'dart:ffi';
import 'dart:ui';

import 'package:flutter/material.dart';

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

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

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

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

class _MyHomePageState extends State<MyHomePage> {
  int number = 0;

  @override
  Widget build(BuildContext context) {
    return Scaffold(
      appBar: AppBar(
        title: Text(widget.title),
      ),
      body: Center(
        child: Column(
          mainAxisAlignment: MainAxisAlignment.center,
          children: <Widget>[
            ShareData(
              params: number.toString(),
              child: TextWidget(),
            ),
            RaisedButton(
              onPressed: () {
                number++;
                setState(() {});
              },
              child: Icon(Icons.add),
            ),
          ],
        ),
      ),
    );
  }
}

class ShareData extends InheritedWidget {
  ShareData({
    Key key,
    @required this.params,
    Widget child,
  }) : super(key: key, child: child);
  final String params;

  @override
  bool updateShouldNotify(ShareData oldWidget) {
    debugPrint('updateShouldNotify');
    if (oldWidget.params != params) {
      return true;
    } else {
      return false;
    }
  }

  static ShareData getSharedData(BuildContext context) {
    return context.dependOnInheritedWidgetOfExactType();
  }
}

class TextWidget extends StatefulWidget {
  _TextWidgetState createState() => _TextWidgetState();
}

class _TextWidgetState extends State<TextWidget> {
  @override
  Widget build(BuildContext context) {
    return Text(
      ShareData.getSharedData(context).params.toString(),
      style: TextStyle(
        fontSize: 30,
      ),
    );
  }

  @override
  void didChangeDependencies() {
    super.didChangeDependencies();
    debugPrint('didChangeDependencies');
  }
}

未完待续