我正在使用LiveTv应用程序。每次尝试使用API加载应用程序时，都会显示“RangeError(索引):无效值:有效值范围为空:0”。因此我了解到，因为在加载应用程序时未加载数据，因此出现错误。
所以我使用了一个叫做Future Builder的东西，但是尽管如此，我仍然遇到相同的错误，但是在加载之后的某个时候，我尝试放置计数器，因为同样需要花费一些时间来构建for循环，但是仍然会发生相同的错误我只是不知道我要去哪里错了
下面是代码，下面是我插入的每个代码的简短说明，请看一下:
Widget build(BuildContext context) {
Widget widgetOptions(int idx) {
Widget _selectedWidget = CircularProgressIndicator();
switch (idx) {
case 0:
_selectedWidget = homePageForBottomNavigator();
break;
case 1:
_selectedWidget = MoviesPageForBottomNavigator();
break;
case 2:
_selectedWidget = TvSHowsPageOfBottomNavigator();
break;
case 3:
_selectedWidget = MusicPageofBottomNavigator();
break;
case 4:
_selectedWidget = NewsPageOfBottomNavigator();
break;
case 5:
_selectedWidget = LifeStylePageOfBottomNavigator();
break;
case 6:
_selectedWidget = SportsPageOfBottomNavigator();
}
return _selectedWidget;
}
return Scaffold(
// key: _drawerKey,
body: SafeArea(
child: SingleChildScrollView(
controller: _scrollController,
child: FutureBuilder(
future: widgetLoadingFunctions(_selectedIndex),
builder: (BuildContext context, AsyncSnapshot snapshot) {
if (snapshot.hasData != null) {
return widgetOptions(_selectedIndex);
} else
return CircularProgressIndicator();
})),
),
drawer: Drawer(),
bottomNavigationBar: BottomNavigationBar(
backgroundColor: Colors.black,
showUnselectedLabels: true,
type: BottomNavigationBarType.shifting,
currentIndex: _selectedIndex,
fixedColor: Colors.amber,
onTap: (int index) {
setState(() {
_selectedIndex = index;
});
},
items: <BottomNavigationBarItem>[
// Icon(
// FontAwesome.facebook_square,
// color: Colors.amber,
// ),
BottomNavigationBarItem(
backgroundColor: Colors.black,
icon: Icon(Icons.home),
title: Text('Home'),
),
BottomNavigationBarItem(
backgroundColor: Colors.black,
icon: Icon(
MaterialCommunityIcons.video_vintage,
),
title: Text(
'Movies',
),
),
BottomNavigationBarItem(
backgroundColor: Colors.black,
icon: Icon(Icons.live_tv),
title: Text(
'Tv shows',
),
),
BottomNavigationBarItem(
backgroundColor: Colors.black,
icon: Icon(Icons.music_video),
title: Text(
'Music',
),
),
BottomNavigationBarItem(
backgroundColor: Colors.black,
icon: Icon(Icons.radio),
title: Text(
'News',
),
),
BottomNavigationBarItem(
backgroundColor: Colors.black,
icon: Icon(
FontAwesome.heartbeat,
),
title: Text(
'LifeStyle',
),
),
BottomNavigationBarItem(
backgroundColor: Colors.black,
icon: Icon(
Ionicons.md_football,
),
title: Text(
'Sports',
),
),
],
),
);
}
}
Future widgetLoadingFunctions(int idx) async {
var _selectedFunxtion;
switch (idx) {
case 0:
_selectedFunxtion = await functionsToBeLoadedForHomePage();
break;
case 1:
_selectedFunxtion = //yet to be implemented
break;
case 2:
_selectedFunxtion = //yet to be implemented
break;
case 3:
_selectedFunxtion = //yet to be implemented
break;
case 4:
_selectedFunxtion = //yet to be implemented
break;
case 5:
_selectedFunxtion = //yet to be implemented
break;
case 6:
_selectedFunxtion = //yet to be implemented
}
return _selectedFunxtion;
}
Future functionsToBeLoadedForHomePage() async {
int counter = 10;
String url =
"https://livetvapi.apyhi.com/api/v3/home?pageLocation=home&countries=IN&app_version=13&"
"user_id=44edc2c905ae163f&package_id=livetv.movies.freemovies.watchtv.tvshows&os_platform=android";
var res = await http
.get(url, headers: {'Authorization': dartJsonWebTokenGenerator()});
if (res.statusCode == 200) {
final _homePage = homePageFromJson(res.body);
for (var homeBannerObject in _homePage.homeBanners) {
setState(() {
_homeBannerObjectMovieIdList.add(homeBannerObject.movieId);
counter = counter - 1;
});
}
for (var homeBannerObject in _homePage.movies) {
setState(() {
_popularMoviesMovieId.add(homeBannerObject.movieId);
counter = counter - 1;
});
}
for (var homeBannerObject in _homePage.series) {
setState(() {
_seriesData.add(homeBannerObject.posterLink);
counter = counter - 1;
});
}
for (var homeBannerObject in _homePage.musicCategories) {
setState(() {
_musicCategories.add(homeBannerObject.categoryName);
counter = counter - 1;
});
}
for (var playListObj in _homePage.musicPlaylists.playlists) {
setState(() {
_musicCategories.add(playListObj.playlistName);
counter = counter - 1;
});
}
for (var publisherObj in _homePage.publishers) {
setState(() {
_popularNewsChannelNames.add(publisherObj.fullName);
counter = counter - 1;
});
}
for (var publisherObj in _homePage.publishers) {
setState(() {
_popularNewsChannelProfilePicUrl.add(publisherObj.profilePicUrl);
counter = counter - 1;
});
}
for (var liveChannelObj in _homePage.liveChannels) {
setState(() {
_liveNewsChannelProfilePicUrl.add(liveChannelObj.publisherProfilePic);
counter = counter - 1;
});
}
for (var liveChannelObj in _homePage.liveChannels) {
setState(() {
_liveNewsChannelNames.add(liveChannelObj.publisherName);
counter = counter - 1;
});
}
setState(() {
_musicPlaylistThemeName = _homePage.musicPlaylists.categoryName;
counter = counter - 1;
return counter == 0 ? "Successfully Exectued" : null;
});
} else
return null;
// print("finished services...........................");
}
最终将被调用的小部件如下:
Widget homePageForBottomNavigator() {
return Stack(
children: <Widget>[
Column(
crossAxisAlignment: CrossAxisAlignment.start,
children: <Widget>[
_buildBody(MediaQuery.of(context).size.height * 0.35,
_homeBannerObjectMovieIdList),
HorizontalListView("Popular movies", _popularMoviesMovieId, false),
HorizontalListView("Popular Tv shows", _seriesData, false),
//infinite list view to be implemented here
HorizontalGridViewOfCardsofGradientColorWithtitle(1, "Music"),
// HorizontalListViewWithoutViewAll(
// _musicPlaylistThemeName , false),
HorizontalListViewWitCircularCards("Popular News channels",
_popularNewsChannelProfilePicUrl, _popularNewsChannelNames),
HorizontalListViewWithoutViewAllForLiveNewsChannels(
"Live News Channels",
_liveNewsChannelProfilePicUrl,
_liveNewsChannelNames),
//VerticalListView(["Latest News"],false),
],
), //end of 1st Widget
Positioned(
bottom: MediaQuery.of(context).size.height * 0.01,
left: MediaQuery.of(context).size.width * 0.3,
child: returnToTopButton()),
],
);
}
最佳答案
在FutureBuilder中，您有错误的条件，(snapshot.hasData!= null)始终为true，应该是这样的:
FutureBuilder(
future: widgetLoadingFunctions(_selectedIndex),
builder: (BuildContext context, AsyncSnapshot snapshot) {
if (snapshot.hasData) {
return widgetOptions(_selectedIndex);
} else
return CircularProgressIndicator();
})),
FutureBuilder(
future: widgetLoadingFunctions(_selectedIndex),
builder: (BuildContext context, AsyncSnapshot snapshot) {
if (snapshot.data != null) {
return widgetOptions(_selectedIndex);
} else
return CircularProgressIndicator();
})),
关于flutter - 为什么我的 FutureBuilder 尽管充满了等待，但仍然不工作？，我们在Stack Overflow上找到一个类似的问题： https://stackoverflow.com/questions/63846698/