flutter - 如何在颤动中重新访问时保存页面状态
问题描述
我有 2 个屏幕，我试图了解如何实现页面状态。例如，在下面的屏幕中，我有 4 个选项，所有选项都将用户带到同一个屏幕，唯一的区别是为每个选项调用的 API 不同以构建列表。我正在尝试处理后退箭头动作，这就是我遇到问题的地方。
用例 - 当用户在屏幕 2 上时，他正在播放歌曲，现在在后按歌曲继续播放。现在，当用户再次从屏幕 1 中选择相同的选项时，我想显示相同的列表而无需重新加载和选择。如果用户选择任何其他选项，它应该表现正常，这是有效的。
解决方案 -
- 我可以对加载的歌曲列表进行硬编码并发送回屏幕 1，然后通过选择再次将其取回，但这会占用大量资源。
- AutomaticKeepAliveClientMixin 我尝试了本教程，但没有帮助或保持状态处于活动状态。
- PageStorage 是我看到的第三个选项，但我发现大部分时间都在我们有标签的应用程序上使用它。
屏幕 1 -
class Dashboard extends StatefulWidget {
int playingId;
Dashboard({this.playingId});
@override
_DashboardState createState() => _DashboardState(playingId);
}
class _DashboardState extends State<Dashboard> {
String appname;
int playingId = 0;
_DashboardState(this.playingId);
// print('${playingId}');
@override
void initState() {
appname="";
// playingId=0;
}
@override
Widget build(BuildContext context) {
return Scaffold(
appBar: AppBar(
elevation: 0,
backgroundColor: AppColors.darkBlue,
centerTitle: true,
title: Text("Tirthankar",
style: TextStyle(color: Colors.white),),
),
backgroundColor: AppColors.styleColor,
body: Column(
children: <Widget>[
// SizedBox(height: 5),
Padding(
padding: const EdgeInsets.all(20),
child: Row(
mainAxisAlignment: MainAxisAlignment.spaceBetween,
children: <Widget>[
CustomGridWidget(
child: Icon(
Icons.file_download,
size: 100,
color: AppColors.styleColor,
),
// image: 'assets/bhaktambar.png',
sizew: MediaQuery.of(context).size.width * .4,
sizeh: MediaQuery.of(context).size.width * .5,
borderWidth: 2,
label: "Bhakti",
onTap: () {
Navigator.of(context).push(
MaterialPageRoute(
builder: (_) => ListPage(appname: "Kids",playingId: playingId,),
),
);
},
),
CustomGridWidget(
child: Icon(
Icons.file_download,
size: 100,
color: AppColors.styleColor,
),
// image: 'assets/bhaktambar.png',
sizew: MediaQuery.of(context).size.width * .4,
sizeh: MediaQuery.of(context).size.width * .5,
borderWidth: 2,
label: "Kids",
onTap: () {
Navigator.of(context).push(
MaterialPageRoute(
builder: (_) => ListPage(appname: "Kids",playingId: playingId,),
),
);
},
),
],
),
),
Padding(
padding: const EdgeInsets.only(
left: 20,
right: 20,
bottom: 20),
child: Row(
mainAxisAlignment: MainAxisAlignment.spaceBetween,
children: <Widget>[
CustomGridWidget(
child: Icon(
Icons.favorite,
size: 100,
color: AppColors.styleColor,
),
// image: 'assets/kids.jpg',
sizew: MediaQuery.of(context).size.width * .4,
sizeh: MediaQuery.of(context).size.width * .5,
borderWidth: 2,
label: "Favorite",
onTap: () {
Navigator.of(context).push(
MaterialPageRoute(
builder: (_) => ListPage(appname: "Songs"),
),
);
},
),
Align(
alignment: Alignment.center,
child: CustomGridWidget(
child: Icon(
Icons.book,
size: 100,
color: AppColors.styleColor,
),
// image: 'assets/vidyasagar.jpg',
sizew: MediaQuery.of(context).size.width * .4,
sizeh: MediaQuery.of(context).size.width * .5,
borderWidth: 2,
onTap: () {
Navigator.of(context).push(
MaterialPageRoute(
builder: (_) => ListPage(appname: "Bhajan"),
),
);
},
),
),
],
),
),
]
),
);
}
Material boxTiles(IconData icon, String name){
return Material(
color: AppColors.mainColor,
elevation: 14.0,
shadowColor: AppColors.styleColor,
borderRadius: BorderRadius.circular(24.0),
child: Center(
child: Padding(
padding: const EdgeInsets.all(8.0),
child:Row(
mainAxisAlignment: MainAxisAlignment.center,
children: <Widget>[
Column(
mainAxisAlignment: MainAxisAlignment.center,
children: <Widget>[
InkWell(
onTap: (){print("tapped"); /* or any action you want */ },
child: Container(
width: 130.0,
height: 10.0,
color : Colors.transparent,
), // container
), //
//Text
Padding(
padding: const EdgeInsets.all(8.0),
child: Text(name,
style:TextStyle(
color: AppColors.styleColor,
fontSize: 20.0,
)
),
),
//Icon
Material(
color: AppColors.styleColor,
borderRadius: BorderRadius.circular(50.0),
child: Padding(padding: const EdgeInsets.all(10.0),
child: Icon(icon, color: AppColors.lightBlue,size: 30,),
),
),
],
)
],
)
),
)
);
}
}
屏幕 2 -
// import 'dart:js';
class ListPage extends StatefulWidget {
String appname;
int playingId;
ListPage({this.appname,this.playingId});
@override
_ListPageState createState() => _ListPageState(appname,playingId);
}
class _ListPageState extends State<ListPage>
with SingleTickerProviderStateMixin,AutomaticKeepAliveClientMixin<ListPage> {
String appname;
int playingId;
bool isPlaying = false;
_ListPageState(this.appname,playingId);
// List<MusicModel> _list1;
List<MusicData> _list;
var _value;
int _playId;
int _songId;
String _playURL;
bool _isRepeat;
bool _isShuffle;
bool _isFavorite;
String _startTime;
String _endTime;
AnimationController _controller;
Duration _duration = new Duration();
Duration _position = new Duration();
final _random = new Random();
AudioPlayer _audioPlayer = AudioPlayer();
@override
void initState() {
_playId = 0;
// _list1 = MusicModel.list;
this._fileUpdate();
// _list = _list1;
_controller =
AnimationController(vsync: this, duration: Duration(microseconds: 250));
_value = 0.0;
_startTime = "0.0";
_endTime = "0.0";
_isRepeat = false;
_isShuffle = false;
_isFavorite = false;
_audioPlayer.onAudioPositionChanged.listen((Duration duration) {
setState(() {
// _startTime = duration.toString().split(".")[0];
_startTime = duration.toString().split(".")[0];
_duration = duration;
// _position = duration.toString().split(".")[0];
});
});
_audioPlayer.onDurationChanged.listen((Duration duration) {
setState(() {
_endTime = duration.toString().split(".")[0];
_position = duration;
});
});
_audioPlayer.onPlayerCompletion.listen((event) {
setState(() {
isPlaying = false;
_position = _duration;
if (_isRepeat) {
_songId = _songId;
} else {
if (_isShuffle) {
var element = _list[_random.nextInt(_list.length)];
_songId = element.id;
} else {
_songId = _songId + 1;
}
}
_player(_songId);
});
});
super.initState();
}
bool get wantKeepAlive => true;
@override
Widget build(BuildContext context) {
super.build(context);
return Scaffold(
appBar: AppBar(
elevation: 0,
backgroundColor: AppColors.mainColor,
centerTitle: true,
leading: IconButton(
icon: Icon(Icons.arrow_back),
onPressed: (){
Navigator.of(context).push(
MaterialPageRoute(
builder: (_) => Dashboard(playingId: _songId),
),
);
},
),
title: Text(
appname,
style: TextStyle(color: AppColors.styleColor),
),
),
backgroundColor: AppColors.mainColor,
body: Stack(
children: <Widget>[
Column(
children: <Widget>[
Padding(
padding: const EdgeInsets.all(24.0),
child: Row(
mainAxisAlignment: MainAxisAlignment.spaceBetween,
children: <Widget>[
CustomButtonWidget(
child: Icon(
Icons.favorite,
color: AppColors.styleColor,
),
size: 50,
onTap: () {},
),
CustomButtonWidget(
image: 'assets/logo.jpg',
size: 100,
borderWidth: 5,
onTap: () {
Navigator.of(context).push(
MaterialPageRoute(
builder: (_) => DetailPage(),
),
);
},
),
CustomButtonWidget(
child: Icon(
Icons.menu,
color: AppColors.styleColor,
),
size: 50,
onTap: () {
Navigator.of(context).push(
MaterialPageRoute(
builder: (_) => HomePage(),
),
);
},
)
],
),
),
slider(),
Padding(
padding: const EdgeInsets.symmetric(horizontal: 15),
child: Row(
mainAxisAlignment: MainAxisAlignment.spaceBetween,
children: <Widget>[
IconButton(
icon: Icon(
_isRepeat ? Icons.repeat_one : Icons.repeat,
color: _isRepeat ? Colors.brown : AppColors.styleColor,
),
onPressed: () {
if (_isRepeat) {
_isRepeat = false;
} else {
_isRepeat = true;
}
},
),
IconButton(
icon: Icon(
isPlaying ? Icons.pause : Icons.play_arrow,
color: AppColors.styleColor,
),
onPressed: () {
if (isPlaying) {
_audioPlayer.pause();
setState(() {
isPlaying = false;
});
} else {
if (!isPlaying){
_audioPlayer.resume();
setState(() {
isPlaying = true;
});
}
}
}),
IconButton(
icon: Icon(
Icons.stop,
color: AppColors.styleColor,
),
onPressed: () {
if (isPlaying){
_audioPlayer.stop();
setState(() {
isPlaying = false;
_duration = new Duration();
});
}
// isPlaying = false;
}),
IconButton(
icon: Icon(
Icons.shuffle,
color:
_isShuffle ? Colors.brown : AppColors.styleColor,
),
onPressed: () {
if (_isShuffle) {
_isShuffle = false;
} else {
_isShuffle = true;
}
}),
],
),
),
Expanded(
//This is added so we can see overlay else this will be over button
child: ListView.builder(
physics:
BouncingScrollPhysics(), //This line removes the dark flash when you are at the begining or end of list menu. Just uncomment for
// itemCount: _list.length,
itemCount: _list == null ? 0 : _list.length,
padding: EdgeInsets.all(12),
itemBuilder: (context, index) {
return GestureDetector(
onTap: () {
_songId = index;
_player(index);
},
child: AnimatedContainer(
duration: Duration(milliseconds: 500),
//This below code will change the color of sected area or song being played.
decoration: BoxDecoration(
color: _list[index].id == _playId
? AppColors.activeColor
: AppColors.mainColor,
borderRadius: BorderRadius.all(
Radius.circular(20),
),
),
//End of row color change
child: Padding(
padding: const EdgeInsets.all(
16), //This will all padding around all size
child: Row(
mainAxisAlignment: MainAxisAlignment
.spaceBetween, //This will allign button to left, else button will be infront of name
children: <Widget>[
Column(
crossAxisAlignment: CrossAxisAlignment.start,
children: <Widget>[
Text(
_list[index].title,
style: TextStyle(
color: AppColors.styleColor,
fontSize: 16,
),
),
Text(
_list[index].album,
style: TextStyle(
color: AppColors.styleColor.withAlpha(90),
fontSize: 16,
),
),
],
),
IconButton(
icon: Icon(_isFavorite
? Icons.favorite
: Icons.favorite_border),
onPressed: () {
if (_isFavorite) {
_isFavorite = false;
} else {
_isFavorite = true;
}
})
//Diabled Play button and added fav button.
// CustomButtonWidget(
// //This is Play button functionality on list page.
// child: Icon(
// _list[index].id == _playId
// ? Icons.pause
// : Icons.play_arrow,
// color: _list[index].id == _playId
// ? Colors.white
// : AppColors.styleColor,
// ),
// size: 50,
// isActive: _list[index].id == _playId,
// onTap: () async {
// _songId = index;
// _player(index);
// },
// )
],
),
),
),
);
},
),
)
],
),
Align(
alignment: Alignment.bottomCenter,
child: Container(
height: 50,
decoration: BoxDecoration(
gradient: LinearGradient(
colors: [
AppColors.mainColor.withAlpha(0),
AppColors.mainColor,
],
begin: Alignment.topCenter,
end: Alignment.bottomCenter,
)),
),
)
],
),
// floatingActionButton: FloatingActionButton(
// child: Icon(Icons.music_note),
// onPressed: () async { // String filePath = await FilePicker.getFilePath();
// int status = await _audioPlayer.play("https://traffic.libsyn.com/voicebot/Jan_Konig_on_the_Jovo_Open_Source_Framework_for_Voice_App_Development_-_Voicebot_Podcast_Ep_56.mp3");
// if (status == 1){
// setState(() {
// isPlaying = true;
// });
// }
// },
// )
);
}
Widget slider() {
return Slider(
activeColor: AppColors.styleColor,
inactiveColor: Colors.lightBlue,
value: _duration.inSeconds.toDouble(),
min: 0.0,
max: _position.inSeconds.toDouble(),
divisions: 10,
onChangeStart: (double value) {
print('Start value is ' + value.toString());
},
onChangeEnd: (double value) {
print('Finish value is ' + value.toString());
},
onChanged: (double value) {
setState(() {
seekToSecond(value.toInt());
value = value;
});
});
}
Future<Void> _fileUpdate() async {
String url =
"azonaws.com/input.json";
String arrayObjsText = "";
try {
eos.Response response;
Dio dio = new Dio();
response = await dio.get(url,options: Options(
responseType: ResponseType.plain,
),);
arrayObjsText = response.data;
print(response.data.toString());
} catch (e) {
print(e);
}
var tagObjsJson = jsonDecode(arrayObjsText)['tags'] as List;
this.setState(() {
_list = tagObjsJson.map((tagJson) => MusicData.fromJson(tagJson)).toList();
});
// return _list;
// print(_list);
}
Future<void> _player(int index) async {
if (isPlaying) {
if (_playId == _list[index].id) {
int status = await _audioPlayer.pause();
if (status == 1) {
setState(() {
isPlaying = false;
});
}
} else {
_playId = _list[index].id;
_playURL = _list[index].songURL;
_audioPlayer.stop();
int status = await _audioPlayer.play(_playURL);
if (status == 1) {
setState(() {
isPlaying = true;
});
}
}
} else {
_playId = _list[index].id;
_playURL = _list[index].songURL;
int status = await _audioPlayer.play(_playURL);
if (status == 1) {
setState(() {
isPlaying = true;
});
}
}
}
String _printDuration(Duration duration) {
String twoDigits(int n) {
if (n >= 10) return "$n";
return "0$n";
}
String twoDigitMinutes = twoDigits(duration.inMinutes.remainder(60));
String twoDigitSeconds = twoDigits(duration.inSeconds.remainder(60));
return "${twoDigits(duration.inHours)}:$twoDigitMinutes:$twoDigitSeconds";
}
void seekToSecond(int second) {
Duration newDuration = Duration(seconds: second);
_audioPlayer.seek(newDuration);
}
}
解决方案
PageStorage 是我看到的第三个选项，但我发现大部分时间都在我们有标签的应用程序上使用它。
您仍然可以根据需要使用此方法，无论是否使用 Tab/底部导航栏。
页面视图类
class Home extends StatefulWidget {
@override
_HomeState createState() => _HomeState();
}
class _HomeState extends State<Home> with SingleTickerProviderStateMixin{
PageController _pageController;
@override
void initState() {
super.initState();
_pageController = PageController();
}
@override
void dispose() {
super.dispose();
_pageController?.dispose();
}
@override
Widget build(BuildContext context) {
return SafeArea(
child: PageView(
controller: _pageController,
physics: NeverScrollableScrollPhysics(), // so the user cannot scroll, only animating when they select an option
children: <Widget>[
Dashboard(playingId: 1, key: PageStorageKey<String>('MyPlayList'), pageController: _pageController), //or the name you want, but you need to give them a key to all the child so it can save the Scroll Position
ListPage(appname: "FirstButton",playingId: 1, key: PageStorageKey<String>('FirstButton'), pageController: _pageController),
ListPage(appname: "SecondButton",playingId: 1, key: PageStorageKey<String>('SecondButton'), pageController: _pageController),
ListPage(appname: "ThirdButton",playingId: 1, key: PageStorageKey<String>('ThirdButton'), pageController: _pageController),
ListPage(appname: "FourthButton",playingId: 1, key: PageStorageKey<String>('FourthButton'), pageController: _pageController)
],
),
)
);
}
}
现在您将 PageController 传递给所有子项（将键和 PageController 属性添加到屏幕 1 和 2）并且在 DashBoard（屏幕 1）中，您可以将按钮的 onTap 从 MaterialRoute 更改为此
onTap: () => widget.pageController.jumpToPage(x), //where x is the index of the children of the PageView you want to see (between 0 and 4 in this case)
在屏幕 2 中，您使用 WillPopScope 包裹所有 Scaffold，因此当用户点击返回而不是关闭路线时，它会返回到索引 0 处的仪表板小部件
@override
Widget build(BuildContext context) {
return WillPopScope(
onWillPop: () {
widget.pageController.jumpToPage(0); // Move back to dashboard (index 0)
return false;
}
child: Scaffold(...)
);
}
如果你想要一些动画效果（animateTo、nextPage、previousPage 等），你可以使用 PageController 的其他方法
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