Flutter 局部路由實現

時間 2019-11-16

原文原文鏈接

Flutter是借鑑React的開發思想實現的，在子組件的插槽上，React有this.props.children，Vue有<slot></slot>。git

固然Flutter也有相似的Widget，那就是Navigator，不過是以router的形式實現（像<router-view></router-view>？？？）。github

Navigator的使用無非3個屬性app

initialRoute: 初始路由
onGenerateRoute: 匹配路由
onUnknownRoute: 404

在實現層面ide

首先：Navigator的高度爲infinity。若是直接父級非最上級也是infinity會產生異常，例如，Scaffold -> Column -> Navigator。因此：Navigator須要附件限制高度，例如：Scaffold -> Column -> Container（height: 300） -> Navigatorui

而後：在onGenerateRoute屬性中，使用第一個BuildContext參數，可以在MaterialApp未設置route的狀況下使用Navigator.pushNamed(nContext, '/efg');跳到對應的子路由中。this

最後：Navigator執行尋找路由順序是 initialRoute -> onGenerateRoute -> onUnknownRoute，這個和React的Route是相似的。code

最後附上源碼router

import 'package:flutter/material.dart';

class NavigatorPage extends StatefulWidget {
  @override
  _NavigatorPageState createState() => _NavigatorPageState();
}

class _NavigatorPageState extends State<NavigatorPage> {
  @override
  Widget build(BuildContext context) {
    return Scaffold(
      appBar: AppBar(
        title: Text('Navigator'),
      ),
      body: Column(
        children: <Widget>[
          Text('Navigator的高度爲infinity'),
          Text('若是直接父級非最上級也是infinity會產生異常'),
          Container(
            height: 333,
            color: Colors.amber.withAlpha(111),
            child: Navigator( // Navigator
              initialRoute: '/abc',
              onGenerateRoute: (val) {
                RoutePageBuilder builder;
                switch (val.name) {
                  case '/abc':
                    builder = (BuildContext nContext, Animation<double> animation, Animation<double> secondaryAnimation) => Column(
                      // 並無在 MaterialApp 中設定 /efg 路由
                      // 由於Navigator的特性 使用nContext 能夠跳轉 /efg
                      children: <Widget>[
                        Text('呵呵呵'),
                        RaisedButton(
                          child: Text('去 /efg'),
                          onPressed: () {
                            Navigator.pushNamed(nContext, '/efg');
                          },
                        )
                      ],
                    );
                  break;
                  case '/efg':
                    builder = (BuildContext nContext, Animation<double> animation, Animation<double> secondaryAnimation) => Row(
                      children: <Widget>[
                        RaisedButton(
                          child: Text('去 /hhh'),
                          onPressed: () {
                            Navigator.pushNamed(nContext, '/hhh');
                          },
                        )
                      ],
                    );
                  break;
                  default:
                    builder = (BuildContext nContext, Animation<double> animation, Animation<double> secondaryAnimation) => Center(
                      child: RaisedButton(
                        child: Text('去 /abc'),
                        onPressed: () {
                          Navigator.pushNamed(nContext, '/abc');
                        },
                      )
                    );
                }
                return PageRouteBuilder(
                  pageBuilder: builder,
                  // transitionDuration: const Duration(milliseconds: 0),
                );
              },
              onUnknownRoute: (val) {
                print(val);
              },
              observers: <NavigatorObserver>[]
            ),
          ),
          Text('Navigator執行尋找路由順序'),
          Text('initialRoute'),
          Text('onGenerateRoute'),
          Text('onUnknownRoute'),
        ],
      ),
    );
  }
}