如何在 Flutter 中收听抽屉打开/关闭动画

Question

Being new to Flutter, I'm doing a learning exercise by re-creating my existing Android app. However I'm having trouble to produce a 'spinning, growing home icon', which should be animated in sync with the drawer open/close animation.

The desired drawer/home-icon behaviour looks like this:

I made this in Android by implementing

DrawerListener.onDrawerSlide(View drawerView, float slideOffset) 

My naive approach to do this in Flutter, is to use a ScaleTransition and a RotationTransition that listen to the same Animation that opens/closes the Drawer.

I can see that ScaffoldState has a DrawerControllerState, but it is private.

final GlobalKey<DrawerControllerState> _drawerKey = new GlobalKey<DrawerControllerState>();

And even if I could somehow access the DrawerControllerState (which I don't know how), I then couldn't access _animationChanged() and _controller because both are private members of DrawerControllerState.

I feel that I'm coming at this in the wrong way, and that there is an better approach that's more natural to Flutter, that I'm unable to see.

Please can anyone describe the Flutter way of implementing this?

Answer 1

You can first refer to other people's replies on stackoverflow here

My solve:

get Drawer status on DrawerWidget

initState() : open drawer
dispose() : close drawer

Stream drawer status by DrawerService Provider

see full code

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

import 'package:provider/provider.dart';


void main() {
  runApp(
    MultiProvider(
      providers: [
        Provider(create: (_) => DrawerService()),
      ],
      child: MyApp(),
    ),
  );
}

class MyApp extends StatelessWidget {
  @override
  Widget build(BuildContext context) {
    return MaterialApp(
      title: 'Flutter Demo',
      theme: ThemeData(
        primarySwatch: Colors.blue,
        visualDensity: VisualDensity.adaptivePlatformDensity,
      ),
      home: MyHomePage(title: 'Flutter Demo Home Page'),
    );
  }
}

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

  final String title;

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

class _MyHomePageState extends State<MyHomePage> {
  DrawerService _drawerService;
  String drawerStatus = 'close';
  @override
  void initState() {
    super.initState();
    _drawerService = Provider.of(context, listen: false);
    _listenDrawerService();
  }

  _listenDrawerService() {
    _drawerService.status.listen((status) {
      if(status) {
        drawerStatus = 'open';
      } else {
        drawerStatus = 'close';
      }
      setState(() { });
    });
  }

  @override
  Widget build(BuildContext context) {
    Color bgColor = Colors.yellow;
    if(drawerStatus == 'open') {
      bgColor = Colors.red;
    }

    return Scaffold(
      appBar: AppBar(
        title: Text(widget.title),
      ),
      drawer: DrawerWidget(),
      body: Container(
        decoration: BoxDecoration(color: bgColor),
        height: 300,
        child: Center(child: Text(drawerStatus),),
      ),
    );
  }
}


class DrawerWidget extends StatefulWidget {
  @override
  _DrawerWidgetState createState() => _DrawerWidgetState();
}

class _DrawerWidgetState extends State<DrawerWidget> {  
  DrawerService _drawerService;

  @override
  void initState() {
    super.initState();
    _drawerService = Provider.of(context, listen: false);
    _drawerService.setIsOpenStatus(true);
  }

  @override
  Widget build(BuildContext context) {
    return Drawer(
      child: Center(child: Text('drawer'),),
    );
  }

  @override
  void dispose() {
    super.dispose();
    _drawerService.setIsOpenStatus(false);
  }
}

class DrawerService {
  StreamController<bool> _statusController = StreamController.broadcast();
  Stream<bool> get status => _statusController.stream;

  setIsOpenStatus(bool openStatus) {
    _statusController.add(openStatus);
  }
}

hope to help some body