颤振ListView，在按back时导致重复值
我有两个类别类型过滤，以便获得帖子列表，然后传递到详细信息页面。我创建了一个新的列表来获得这个帖子颤振ListView，在按back时导致重复值,listview,flutter,Listview,Flutter,我有两个类别类型过滤，以便获得帖子列表，然后传递到详细信息页面。我创建了一个新的列表来获得这个帖子 // I believed this is the reason of the error, when it back it loop again. list<Post> cat1 = []; list<Post> cat2 = []; ........ Widget _postList ( List<Post> posts ) { for ( v
// I believed this is the reason of the error, when it back it loop again.
list<Post> cat1 = [];
list<Post> cat2 = [];
........
Widget _postList ( List<Post> posts ) {
for ( var item in posts) {
if (widget.cat1postsids.contains(item.id)) {
cat1.add(item);
}}
return Container(
child: _fetchPostbyCat1( cat1 )
);
}
Widget _fetchPostbyCat1 ( List<Post> posts ) {
for ( var item in posts) {
if (widget.cat2postsids.contains(item.id)) {
cat2.add(item);
}}
return Container(
child: _getPost( cat2 )
);
}
Widget _getPost ( List<Post> posts ) {
return ListView.builder ....
}
class PostListView extends StatefulWidget {
final List selectedIDS;
final String name;
PostListView(this.selectedIDS, this.name);
@override
PostListViewState createState() => new PostListViewState();
}
class PostListViewState extends State<PostListView> {
PostApi postapi;
List <Post> getPostByCat1 = [];
List <Post> getPostByCat2 = [];
@override
void initState() {
super.initState();
postapi = PostApi();
}
@override
Widget build(BuildContext context) {
return Scaffold(
appBar: AppBar(
title: Text('Post'),
leading: new IconButton(
icon: new Icon(Icons.arrow_back),
onPressed: () { Navigator.pop(context, true); })),
body: NestedScrollView(
headerSliverBuilder: (BuildContext context, bool innerBoxIsScrolled) {
return [ SliverList(
delegate: SliverChildListDelegate([
Container(
child: Padding(
padding: EdgeInsets.only(left: 20.0, top: 30.0, right: 20.0, bottom: 30.0 ),
child: Column(
mainAxisSize: MainAxisSize.max,
crossAxisAlignment: CrossAxisAlignment.stretch,
children: <Widget>[
AutoSizeText( 'LATEST POST', maxLines: 2,
textAlign: TextAlign.center,
style: TextStyle (fontSize: 28, color: Colors.black, fontWeight: FontWeight.w700))
])),
decoration: new BoxDecoration(
border: Border(
bottom: BorderSide(width: 1.0, color: Colors.grey ))))]))];},
body: SafeArea(
child: SizedBox(
child: Column(
mainAxisAlignment: MainAxisAlignment.spaceEvenly,
mainAxisSize: MainAxisSize.min,
crossAxisAlignment: CrossAxisAlignment.start,
children: <Widget>[
Expanded(
child: ListView (
children: <Widget>[
Container(
child: FutureBuilder(
future: postapi.fetchAllPost(),
builder: (BuildContext context, AsyncSnapshot snapshot) {
if( snapshot.connectionState == ConnectionState.done ) {
if( snapshot.hasError ) {
return returnerror( snapshot.error.toString());
}
}
if( snapshot.hasData) {
return _postList( snapshot.data );
}
return Center ( child: CircularProgressIndicator());
}))]))])))));
}
Widget _postList ( List<Post> posts ) {
for ( var item in posts) {
if (widget.name.contains(item.catname)) {
getPostByCat1.add(item);
}}
return Container( child: _getPosts(getPostByCat1));
}
Widget _getPosts (List<Post> posts) {
for(var item in getPostByCat1){
if(widget.selectedIDS.contains(item.post_id)) {
getPostByCat2.add(item);
}
} return Container(child: _listPosts(getPostByCat2));
}
Widget _listPosts (List<Post> posts) {
return ListView.builder(
physics: ClampingScrollPhysics(),
shrinkWrap: true,
itemCount: posts.length,
itemBuilder: ( BuildContext context, int index ) {
var imgUrl = ApiUtil.MAIN_API_URL + ApiUtil.IMAGE_PATH + posts[index].image;
String postID = posts[index].id;
String postname = posts[index].name;
return new Card (
child: InkWell(
onTap: () {
Navigator.push(context, MaterialPageRoute(
builder: (context) => PostDetails(postID, postname)));},
child: Padding(
padding: const EdgeInsets.all(10.0),
child: new Row(
crossAxisAlignment: CrossAxisAlignment.start,
children: <Widget>[
Expanded(
flex: 1,
child: Image.network(imgUrl),
),
Expanded(
flex: 3,
child: Padding(
padding: EdgeInsets.all(10.0),
child: ListTile(
title: new Text(posts[index].name,
style: TextStyle(
fontSize: 22,
fontWeight: FontWeight.w700
),
),
subtitle: new Text(posts[index].subname,
style: TextStyle(
fontSize: 16,
)))))])))); });}
}
onPressed: () {
Navigator.pop(context, true);
return Future.value(true);
}
// I believed this is the reason of the error, when it back it loop again.
list<Post> cat1 = [];
list<Post> cat2 = [];
........
Widget _postList ( List<Post> posts ) {
for ( var item in posts) {
if (widget.cat1postsids.contains(item.id)) {
cat1.add(item);
}}
return Container(
child: _fetchPostbyCat1( cat1 )
);
}
Widget _fetchPostbyCat1 ( List<Post> posts ) {
for ( var item in posts) {
if (widget.cat2postsids.contains(item.id)) {
cat2.add(item);
}}
return Container(
child: _getPost( cat2 )
);
}
Widget _getPost ( List<Post> posts ) {
return ListView.builder ....
}
class PostListView extends StatefulWidget {
final List selectedIDS;
final String name;
PostListView(this.selectedIDS, this.name);
@override
PostListViewState createState() => new PostListViewState();
}
class PostListViewState extends State<PostListView> {
PostApi postapi;
List <Post> getPostByCat1 = [];
List <Post> getPostByCat2 = [];
@override
void initState() {
super.initState();
postapi = PostApi();
}
@override
Widget build(BuildContext context) {
return Scaffold(
appBar: AppBar(
title: Text('Post'),
leading: new IconButton(
icon: new Icon(Icons.arrow_back),
onPressed: () { Navigator.pop(context, true); })),
body: NestedScrollView(
headerSliverBuilder: (BuildContext context, bool innerBoxIsScrolled) {
return [ SliverList(
delegate: SliverChildListDelegate([
Container(
child: Padding(
padding: EdgeInsets.only(left: 20.0, top: 30.0, right: 20.0, bottom: 30.0 ),
child: Column(
mainAxisSize: MainAxisSize.max,
crossAxisAlignment: CrossAxisAlignment.stretch,
children: <Widget>[
AutoSizeText( 'LATEST POST', maxLines: 2,
textAlign: TextAlign.center,
style: TextStyle (fontSize: 28, color: Colors.black, fontWeight: FontWeight.w700))
])),
decoration: new BoxDecoration(
border: Border(
bottom: BorderSide(width: 1.0, color: Colors.grey ))))]))];},
body: SafeArea(
child: SizedBox(
child: Column(
mainAxisAlignment: MainAxisAlignment.spaceEvenly,
mainAxisSize: MainAxisSize.min,
crossAxisAlignment: CrossAxisAlignment.start,
children: <Widget>[
Expanded(
child: ListView (
children: <Widget>[
Container(
child: FutureBuilder(
future: postapi.fetchAllPost(),
builder: (BuildContext context, AsyncSnapshot snapshot) {
if( snapshot.connectionState == ConnectionState.done ) {
if( snapshot.hasError ) {
return returnerror( snapshot.error.toString());
}
}
if( snapshot.hasData) {
return _postList( snapshot.data );
}
return Center ( child: CircularProgressIndicator());
}))]))])))));
}
Widget _postList ( List<Post> posts ) {
for ( var item in posts) {
if (widget.name.contains(item.catname)) {
getPostByCat1.add(item);
}}
return Container( child: _getPosts(getPostByCat1));
}
Widget _getPosts (List<Post> posts) {
for(var item in getPostByCat1){
if(widget.selectedIDS.contains(item.post_id)) {
getPostByCat2.add(item);
}
} return Container(child: _listPosts(getPostByCat2));
}
Widget _listPosts (List<Post> posts) {
return ListView.builder(
physics: ClampingScrollPhysics(),
shrinkWrap: true,
itemCount: posts.length,
itemBuilder: ( BuildContext context, int index ) {
var imgUrl = ApiUtil.MAIN_API_URL + ApiUtil.IMAGE_PATH + posts[index].image;
String postID = posts[index].id;
String postname = posts[index].name;
return new Card (
child: InkWell(
onTap: () {
Navigator.push(context, MaterialPageRoute(
builder: (context) => PostDetails(postID, postname)));},
child: Padding(
padding: const EdgeInsets.all(10.0),
child: new Row(
crossAxisAlignment: CrossAxisAlignment.start,
children: <Widget>[
Expanded(
flex: 1,
child: Image.network(imgUrl),
),
Expanded(
flex: 3,
child: Padding(
padding: EdgeInsets.all(10.0),
child: ListTile(
title: new Text(posts[index].name,
style: TextStyle(
fontSize: 22,
fontWeight: FontWeight.w700
),
),
subtitle: new Text(posts[index].subname,
style: TextStyle(
fontSize: 16,
)))))])))); });}
}
class PostListView扩展了StatefulWidget{
最终选定的列表ID；
最后的字符串名；
PostListView（this.selectedds，this.name）；
@凌驾
PostListViewState createState（）=>新建PostListViewState（）；
}
类PostListViewState扩展了状态{
PostApi PostApi；
列表getPostByCat1=[]；
列表getPostByCat2=[]；
@凌驾
void initState（）{
super.initState（）；
postapi=postapi（）；
}
@凌驾
小部件构建（构建上下文）{
返回脚手架(
appBar:appBar(
标题：文本（“帖子”），
领先：新图标按钮(
图标：新图标（图标。箭头返回），
onPressed:（）{Navigator.pop（context，true）；}）），
正文：嵌套滚动视图(
headerSliverBuilder：（BuildContext上下文，boolInnerBoxIsCrolled）{
返回[切片列表](
委托：SliverChildListDelegate([
容器(
孩子：填充(
填充：仅限边缘设置（左侧：20.0，顶部：30.0，右侧：20.0，底部：30.0），
子：列(
mainAxisSize:mainAxisSize.max，
crossAxisAlignment:crossAxisAlignment.stretch，
儿童：[
AutoSizeText（'LATEST POST'，maxLines:2，
textAlign:textAlign.center，
样式：TextStyle（fontSize:28，颜色：Colors.black，fontWeight:fontWeight.w700））
])),
装饰：新盒子装饰(
边界：边界(
底部：边框边（宽度：1.0，颜色：Colors.grey））]；}，
正文：安全区(
孩子：大小盒子(
子：列(
mainAxisAlignment:mainAxisAlignment.space，
mainAxisSize:mainAxisSize.min，
crossAxisAlignment:crossAxisAlignment.start，
儿童：[
扩大(
子：ListView(
儿童：[
容器(
孩子：未来建设者(
future:postapi.fetchAllPost（），
生成器：（BuildContext上下文，异步快照）{
if（snapshot.connectionState==connectionState.done）{
if（snapshot.hasError）{
返回returnerror（snapshot.error.toString（））；
}
}
if（snapshot.hasData）{
返回_postList（snapshot.data）；
}
返回中心（子项：CircularProgressIndicator（））；
}))]))])))));
}
小部件_postList（列表帖子）{
用于（职位中的var项目）{
if（widget.name.contains（item.catname））{
getPostByCat1.add（项）；
}}
返回容器（子项：_getPosts（getPostByCat1））；
}
小部件_getPosts（列出帖子）{
for（getPostByCat1中的变量项）{
if（widget.selectedds.contains（item.post\u id））{
getPostByCat2.add（项）；
}
}返回容器（子项：_listPosts（getPostByCat2））；
}
小部件_列表帖子（列表帖子）{
返回ListView.builder(
物理：ClampingScrollPhysics（），
收缩膜：对，
itemCount:posts.length，
itemBuilder:（构建上下文，int索引）{
var imgUrl=ApiUtil.MAIN\u API\u URL+ApiUtil.IMAGE\u PATH+posts[index].IMAGE；
字符串postID=posts[index].id；
字符串postname=posts[index].name；
归还新卡(
孩子：InkWell(
onTap:（）{
Navigator.push（上下文、MaterialPage路由）(
生成器：（上下文）=>PostDetails（postID，postname））；}，
孩子：填充(
填充：常数边集全部（10.0），
孩子：新的一排(
crossAxisAlignment:crossAxisAlignment.start，
儿童：[
扩大(
弹性：1，
子：Image.network（imgUrl），
),
扩大(
弹性：3，
孩子：填充(
填充：所有边缘设置（10.0），
孩子：ListTile(
标题：新文本（发布[索引]）。名称，
样式：TextStyle(
尺寸：22，
fontWeight:fontWeight.w700
),
),
字幕：新文本（帖子[索引]）。子名称，
样式：TextStyle(
尺寸：16，
)))))])))); });}
}