最近一段时间我正面临一些问题。我正在为我的应用程序使用scoped_model软件包。但是我遇到的问题是，当我搜索东西或将屏幕转到横向模式时，它会生成两次。
这种情况发生时，我会得到重复的json，因为它会重建两次。
搜索并返回自定义滚动视图后，我再遇到另一个问题。我不能再向下滚动。
我写了以下文件：
main.dart：
class GetRelations extends StatefulWidget {
@override
RelationsPage createState() => RelationsPage();
}
class RelationsPage extends State<GetRelations> {
final RelationScopedModel relationScopedModel = RelationScopedModel();
@override
Widget build(BuildContext context) {
relationScopedModel.initializeValues();
return Scaffold(
body: ScopedModel<RelationScopedModel>(
model: relationScopedModel,
child: Container(
child: SearchScreen(),
),
),
);
}
}
search_screen.dart：
class SearchScreen extends StatefulWidget {
@override
SearchScreenState createState() {
return new SearchScreenState();
}
}
class SearchScreenState extends State<SearchScreen> {
final RelationScopedModel relationScopedModel = RelationScopedModel();
ScrollController controller;
int page = 0;
bool atEnd = false;
@override
void initState() {
super.initState();
controller = new ScrollController()..addListener(_scrollListener);
}
@override
void dispose() {
super.dispose();
controller.dispose();
}
void _scrollListener() {
var props = RelationScopedModel.of(context);
/// When reload we check if skip == 0, if skip is 0 then page has to become 0 too.
if (props.skip == 0) {
page = 0;
}
/// Checking if user is at the end of the screen, then let's receive some new content.
if (controller.position.pixels == controller.position.maxScrollExtent) {
/// If it is at the end, we have to set atEnd to true.
if (props.atTheEnd == true) {
atEnd = props.atTheEnd;
return;
}
/// If it has no more pages, return.
if (props.hasMorePages == false) {
return;
}
/// If it is has more stuff, load it in!
if (!props.isLoadingMore && props.hasMorePages) {
page++;
props.getRelations(props.search, page);
}
}
}
@override
Widget build(BuildContext context) {
/// Go back to last page by using WillPopScope.
return WillPopScope(
onWillPop: () {
Navigator.pop(context);
},
child: new Scaffold(
drawer: new DrawerOnly(),
/// We are using Scoped Model to load the json in the sliver list.
body: ScopedModelDescendant<RelationScopedModel>(
builder: (context, child, model) {
return CustomScrollView(
controller: controller,
slivers: <Widget>[
SliverAppBar(
title: SearchWidget(
performSearch: model.getRelations,
),
floating: true,
pinned: true,
),
model.isLoading && model.atTheEnd
? SliverFillRemaining(
child: Center(
child: CircularProgressIndicator(),
),
)
: model.getRelationCount() < 1
? SliverFillRemaining(
child: Center(
child: Text(
model.statusText,
style: Theme.of(context).textTheme.headline,
),
),
)
: SliverList(
delegate: SliverChildBuilderDelegate(
(context, index) {
if (index == model.getRelationCount() + 1) {
if (model.hasMorePages == true) {
return Padding(
padding: const EdgeInsets.symmetric(
vertical: 16.0),
child: Center(
child: CircularProgressIndicator()),
);
}
return Container(width: 0, height: 0);
} else if (index == 0) {
return Container(
padding: const EdgeInsets.all(16),
decoration: BoxDecoration(
border: Border(
bottom: BorderSide(
color: Colors.grey[300]))),
child: Text(
"Relaties",
style: Theme.of(context)
.textTheme
.body2
.copyWith(color: Colors.white),
),
);
} else {
return Container(
child: Column(
children: <Widget>[
InkWell(
child: RelationItem(
model.relation[index - 1]),
onTap: () {
var id =
model.relation[index - 1].id;
Navigator.of(context).push(
new MaterialPageRoute(
builder: (BuildContext
context) =>
new DetailScreen(id)));
},
),
],
),
);
}
},
childCount: model.getRelationCount() + 2,
),
)
],
);
},
),
),
);
}
}
search.dart（这是我的searchwidget）：
class SearchWidget extends StatelessWidget { final performSearch;
const SearchWidget({Key key, @required this.performSearch}) : super(key: key);
@override Widget build(BuildContext context) {
print('wat gebeurt er');
return Card(
elevation: 3.0,
shape: RoundedRectangleBorder(
borderRadius: BorderRadius.all(Radius.circular(2.0)),
),
child: Padding(
padding: EdgeInsets.symmetric(horizontal: 15.0),
child: Row(
mainAxisAlignment: MainAxisAlignment.spaceBetween,
children: <Widget>[
GestureDetector(
child: Icon(
Icons.search,
color: Colors.white,
),
onTap: () {},
),
SizedBox(
width: 10.0,
),
Expanded(
child: TextField(
decoration: InputDecoration(
hintStyle: TextStyle(fontSize: 14.0, color: Colors.white),
border: InputBorder.none,
hintText: "Zoeken..."),
onChanged: (String search) {
if (search.length > 2) {
performSearch(search);
}
if (search.length == 0) {
performSearch(search);
}
},
),
),
InkWell(
onTap: () {
Navigator.of(context).push(
MaterialPageRoute(builder: (context) => SettingsScreen()));
},
child: Icon(
FontAwesomeIcons.slidersH,
color: Colors.white,
),
),
],
),
),
); } }
relation_scoped_model.dart：
class RelationScopedModel extends Model {
List<GetRelation> _relation = [];
List<GetContacts> _contacts = [];
List<GetLocations> _locations = [];
bool _isLoading = false;
String _statusText = "Start met zoeken...";
bool _hasMorePages = true;
int _skip = 0;
int skipMore = 0;
String _search;
bool _isLoadingMore = false;
bool atTheEnd = false;
List<Map<String, String>> _listingTypeList = [
{"name": "Buy", "value": "buy"},
{"name": "Rent", "value": "rent"},
];
String _listingType;
List<Map<String, String>> _sortList = [
{"name": "Relevancy", "value": "relevancy"},
{"name": "Bedroom (Ascending)", "value": "bedroom_lowhigh"},
{"name": "Bedroom (Descending)", "value": "bedroom_highlow"},
{"name": "Price (Ascending)", "value": "price_lowhigh"},
{"name": "Price (Descending)", "value": "price_highlow"},
{"name": "Newest", "value": "newest"},
{"name": "Oldest", "value": "oldest"},
{"name": "Random", "value": "random"},
{"name": "Distance", "value": "distance"}
];
String _sort;
List<GetRelation> get relation => _relation;
List<GetContacts> get contacts => _contacts;
List<GetLocations> get locations => _locations;
bool get isLoading => _isLoading;
String get statusText => _statusText;
bool get hasMorePages => _hasMorePages;
String get search => _search;
int get skip => _skip;
bool get isLoadingMore => _isLoadingMore;
List<Map<String, String>> get listingTypeList => _listingTypeList;
String get listingType => _listingType;
List<Map<String, String>> get sortList => _sortList;
String get sort => _sort;
int getRelationCount() => _relation.length;
void initializeValues() async {
_relation.clear();
SharedPreferences prefs = await SharedPreferences.getInstance();
_listingType = prefs.getString('listingType') ?? 'rent';
_sort = prefs.getString('sort') ?? 'relevancy';
getRelations(search);
}
var _skiptotal = 10;
var lastSearch;
Future<dynamic> _getData(String search, [int page = 0]) async {
/// When page is 0 we don't have to skip content, if page is 1 or higher it will have to skip content
if (page != 0) {
var skipPage = page * _skiptotal;
_skip = skipPage;
}
/// If page == 0, we have to set page and _skip to 0.
else {
_skip = 0;
page = 0;
}
/// When nothing is filled in the input search, we have to set search to single quotes because otherwise it will search on null.
if (search == null) {
search = '';
}
if (lastSearch != search) {
_relation.clear();
lastSearch = '';
lastSearch = search;
page + 1;
}
String _credentials;
SharedPreferences pref = await SharedPreferences.getInstance();
_credentials = (pref.getString("credentials") ?? "Empty");
var res = await http.get(
Uri.encodeFull("$cf_api_RelationsUrl" +
"?$cf_api_SkipParameter=$_skip&$cf_api_SearchParameter=$search&$cf_api_LimitParameter=10"),
headers: {
"content-type": "application/json",
"accept": "application/json",
'cookie': '$_credentials'
});
var decodedJson = json.decode(res.body, reviver: (k, v) {
if (k == "status" && v == false) {
_hasMorePages = false;
return v;
} else {
return v;
}
});
if (_hasMorePages == false) {
return decodedJson;
} else {
List list = List();
list = json.decode(res.body) as List;
if (list.length < 10) {
atTheEnd = true;
_hasMorePages = false;
return decodedJson;
}
}
return decodedJson;
}
Future getRelations(String search, [int page = 0]) async {
if (page == 0) {
page = 0;
_isLoading = true;
_relation.clear();
} else {
_isLoadingMore = true;
}
_search = search;
var responseData = await _getData(search, page);
notifyListeners();
var result = responseData
.map(
(data) => serializers.deserializeWith(GetRelation.serializer, data))
.toList();
result.forEach((relations) {
_relation.add(relations);
});
if (result.isEmpty) {
_statusText = "Nothing Found";
}
if (page == 0) {
_isLoading = false;
} else {
_isLoadingMore = false;
}
if (atTheEnd == true) {
return true;
}
// notifyListeners();
}
void setListingType(String value) async {
_listingType = value;
getRelations(search);
notifyListeners();
SharedPreferences prefs = await SharedPreferences.getInstance();
prefs.setString('listingType', _listingType);
}
void setSort(String value) async {
_sort = value;
getRelations(search);
notifyListeners();
SharedPreferences prefs = await SharedPreferences.getInstance();
prefs.setString('sort', _sort);
}
/// Wraps [ScopedModel.of] for this [Model].
static RelationScopedModel of(BuildContext context) =>
ScopedModel.of<RelationScopedModel>(context);
}
我猜测问题是我的scopedmodeldescendant不在init状态。但是我不确定，我希望有人知道这段代码有什么问题。
预先感谢
问候，
Jente
更新： 当我在initializeValues（）的relation_scoped_model中将atTheEnd设置为false并将hasMorePages设置为true时，我的customcrollview工作正常。
我仍然面临的唯一问题是我得到了重复，这是因为我的屏幕重建了两次。
答案 0 :(得分：0)
使用作用域模型时，应使用作用域模型后代包装应该对更改一一响应的小部件。这样，只有那些小部件可以重建，而不是整个页面重建。