我需要刷新后才能更新数据。我正在从json url提取数据并将数据保存到db并在listview builder中显示，但是每当json api正在更新数据时，数据都是静态的，因此请帮助我。我使用了here中的示例。下面是我的代码
articles.dart
class Articleslist extends StatefulWidget {
@override
Articleslist({this.title}) : super();
final String title;
_OurArticleslistPageState createState() => new _OurArticleslistPageState();
}
class _OurArticleslistPageState extends State<Articleslist> {
final GlobalKey<RefreshIndicatorState> _refreshIndicatorKey =
new GlobalKey<RefreshIndicatorState>();
ScrollController _scrollController = new ScrollController();
List<ArticleslistData> articleslist = [];
var dbHelper = DBHelper();
@override
void initState() {
if (Platform.isAndroid) {
FirebaseAdMob.instance.initialize(appId: appIdForAndroid);
} else if (Platform.isIOS) {
FirebaseAdMob.instance.initialize(appId: appIdForIOS);
}
_getOurArticleslist(0);
dbHelper.countItems().then((val) {
if (val == 0) {
_getOurArticleslist(0);
} else {
dbHelper.readdb().then((list) {
print("The Last nid and Pageno is : ");
print(list[list.length - 1]['nid']);
print(list[list.length - 1]['pageno']);
pageno = list[list.length - 1]['pageno'] + 1;
_getOurArticleslist1(pageno);
});
}
});
_scrollController.addListener(() {
if (_scrollController.position.pixels ==
_scrollController.position.maxScrollExtent) {
dbHelper.readdb().then((list) {
pageno = list[list.length - 1]['pageno'] + 1;
_getOurArticleslist1(pageno);
});
// if we scroll up to bottom of the page
}
});
super.initState();
}
@override
void dispose() {
// _scrollController.dispose();
super.dispose();
}
_getOurArticleslist1(int pageno) async {
if (this.mounted) {
var data = await http.get('$BaseUrl/rest/articles?page=$pageno');
if (data.contentLength == 5) {
print('ಲೋಡ್ ಮಾಡಲು ಇನ್ನಷ್ಟು ಲೇಖನಗಳು ಇಲ್ಲ');
} else {
if (context != null) {
Scaffold.of(context).showSnackBar(new SnackBar(
content: new Text("ಲೋಡ್ ಮಾಡಲಾಗುತ್ತಿದೆ. ದಯವಿಟ್ಟು ನಿರೀಕ್ಷಿಸಿ..."),
backgroundColor: Colors.deepOrange,
duration: Duration(milliseconds: 1600),
));
}
}
if (data.statusCode == 200) {
if (this.mounted) {
setState(() {
var jsonData = json.decode(utf8.decode(data.bodyBytes));
for (var e in jsonData) {
if (e['field_image'] == '[]') {
e['field_image'] = 'No img';
}
ArticleslistData article = ArticleslistData(
e['title'],
e['nid'],
e['field_image'],
e['created'],
e['uid'],
e['totalcount'],
pageno);
articleslist.add(article);
dbHelper.saveArticle(article);
}
});
}
} else {
throw Exception('Failed to load data ');
}
if (this.mounted) {
return articleslist;
}
}
return null();
}
_getOurArticleslist(int pageno) async {
if (this.mounted) {
var data = await http.get('$BaseUrl/rest/articles?page=$pageno');
if (data.contentLength == 5) {
print('ಲೋಡ್ ಮಾಡಲು ಇನ್ನಷ್ಟು ಲೇಖನಗಳು ಇಲ್ಲ');
} else {
if (context != null) {
Scaffold.of(context).showSnackBar(new SnackBar(
content: new Text("ಲೋಡ್ ಮಾಡಲಾಗುತ್ತಿದೆ. ದಯವಿಟ್ಟು ನಿರೀಕ್ಷಿಸಿ..."),
backgroundColor: Colors.deepOrange,
duration: Duration(milliseconds: 1600),
));
}
}
if (data.statusCode == 200) {
var listfromdb;
if (this.mounted) {
setState(() {
var jsonData = json.decode(utf8.decode(data.bodyBytes));
dbHelper.readdb().then((list) {
listfromdb = list;
print('Listfromdb count is');
print(listfromdb.length);
if (listfromdb.length == 0) {
print('\n\nInside listfromdb.length == 0\n\n');
for (var e in jsonData) {
if (e['field_image'].toString() == '[]') {
e['field_image'] = 'No img';
}
ArticleslistData article = ArticleslistData(
e['title'],
e['nid'],
e['field_image'],
e['created'],
e['uid'],
e['totalcount'],
// e['body'],
pageno);
articleslist.add(article);
dbHelper.saveArticle(article);
}
}
if (pageno == 0) {
print('Inside pageno == 0\n\n');
for (var e = 0; e < jsonData.length; e++) {
for (var i = 0; i < listfromdb.length; i++) {
print(jsonData[e]['nid'] + ',' + listfromdb[i]['nid']);
if (jsonData[e]['nid'] == listfromdb[i]['nid']) {
break;
} else {
if (jsonData[e]['field_image'].toString() == '[]') {
jsonData[e]['field_image'] = 'No img';
}
ArticleslistData article = ArticleslistData(
jsonData[e]['title'],
jsonData[e]['nid'],
jsonData[e]['field_image'],
jsonData[e]['created'],
jsonData[e]['uid'],
jsonData[e]['totalcount'],
listfromdb[listfromdb.length - 1]['pageno']);
print(article);
articleslist.add(article);
dbHelper.saveArticle(article);
e++;
}
}
break;
}
} else if (listfromdb.length != 0) {
print(' Inside listfromdb.length != 0\n\n');
for (var e in jsonData) {
if (e['field_image'].toString() == '[]') {
e['field_image'] = 'No img';
}
print(e['nid']);
ArticleslistData article = ArticleslistData(
e['title'],
e['nid'],
e['field_image'],
e['created'],
e['uid'],
e['totalcount'],
pageno);
articleslist.add(article);
dbHelper.saveArticle(article);
}
}
});
});
}
} else {
throw Exception('Failed to load data ');
}
if (this.mounted) {
return articleslist;
}
}
return null;
}
Future<List<ArticleslistData>> fetchEmployeesFromDatabase() async {
await new Future.delayed(const Duration(seconds: 1));
var dbHelper = DBHelper();
Future<List<ArticleslistData>> articles = dbHelper.getArticles();
return articles;
}
@override
Widget build(BuildContext context) {
return new Scaffold(
body: Container(
padding: new EdgeInsets.all(5.0),
child: new FutureBuilder<List<ArticleslistData>>(
future: fetchEmployeesFromDatabase(),
builder: (context, snapshot) {
print(snapshot.data);
if (snapshot.hasData) {
print('Snapshot has data');
if (snapshot.data == []) {
return new Text(
'Poor Connection, Please wait or Try refreshing the content');
} else {
return RefreshIndicator(
key: _refreshIndicatorKey,
onRefresh: fetchEmployeesFromDatabase,
child: ListView.builder(
scrollDirection: Axis.vertical,
shrinkWrap: true,
controller: _scrollController,
itemCount: snapshot.data.length,
itemBuilder: (context, index) {
var imgUrl = snapshot.data[index].img.toString();
imgUrl = imgUrl.replaceAll("\"", "");
imgUrl = BaseUrl + imgUrl.toString();
print('\n Image Url: $imgUrl \n');
var title = snapshot.data[index].title;
title = title.replaceAll(""", '"');
title = title.replaceAll("'", "'");
var views = snapshot.data[index].totalcount;
return Container(
child: SizedBox.fromSize(
// child: GestureDetector(
child: new Card(
elevation: 2.0,
child: Column(
children: <Widget>[
GestureDetector(
onTap: () {
print('Tapped : ${snapshot.data[index].nid}');
print(index);
Navigator.push(
context,
new MaterialPageRoute(
builder: (context) => DetailPage(
snapshot.data[index].title,
snapshot.data[index].img,
snapshot.data[index].nid,
snapshot.data[index].uid,
)));
},
child: ListTile(
contentPadding: EdgeInsets.symmetric(
horizontal: 20.0, vertical: 25.0),
leading: Container(
padding: EdgeInsets.only(right: 12.0),
decoration: new BoxDecoration(
border: new Border(
right: new BorderSide(
width: 1.0, color: Colors.grey)),
),
child: imgUrl == 'No img'
? new Image.asset(
'images/placeholder.png',
height: 100,
width: 100,
)
: FadeInImage.assetNetwork(
placeholder: 'images/placeholder.png',
image: imgUrl,
fit: BoxFit.fitWidth,
),
),
title: Text(
title,
style: TextStyle(
fontSize: 16,
color: Colors.black,
fontWeight: FontWeight.bold),
overflow: TextOverflow.ellipsis,
maxLines: 2,
),
subtitle: Text(
'ಲೇಖಕರು : ' + snapshot.data[index].uid,
style: TextStyle(
fontSize: 12,
color: Colors.grey,
fontWeight: FontWeight.bold),
textAlign: TextAlign.left,
overflow: TextOverflow.ellipsis,
maxLines: 1,
),
),
),
Divider(height: .0),
Row(
mainAxisAlignment: MainAxisAlignment.spaceAround,
children: <Widget>[
Row(
mainAxisAlignment: MainAxisAlignment.spaceBetween,
children: <Widget>[
new Icon(Icons.remove_red_eye,size: 14.0),
Center(
child: views == null
? new Text('')
: new Text(' ${snapshot.data[index].totalcount} ಓದು'),
)
],
),
SizedBox(
height: 40,
child: FlatButton(
child: Row(
children: <Widget>[
// Padding(
// padding: EdgeInsets.all(8.0),
// child:
// ),
Image.asset('images/share-icons.png',scale: 5.0),
new Text(' ಹಂಚಿಕೊಳ್ಳಿ')
],
),
onPressed: (){
var nid = articleslist[index].nid;
var url = '$BaseUrl/node/' + nid;
Share.share(url);
}),
),
],
),
],
),
),
),
);
},
),
);
}
} else if (snapshot.hasError) {
return new Text(
"${snapshot.error}",
style: TextStyle(fontSize: 22, color: Colors.black),
);
}
return new Container(
alignment: AlignmentDirectional.center,
child: new CircularProgressIndicator(),
);
},
),
));
}
}
class ArticleslistData {
final String title;
final String nid;
final String img;
final String created;
final String uid;
final String totalcount;
int pageno;
ArticleslistData(this.title, this.nid, this.img, this.created, this.uid,
this.totalcount, this.pageno);
}
dbhelper.dart
import 'dart:async';
import 'dart:io' as io;
import 'package:path/path.dart';
import 'package:models/Article/articleslist.dart';
import 'package:sqflite/sqflite.dart';
import 'package:path_provider/path_provider.dart';
class DBHelper {
static Database _db;
Future<Database> get db async {
if (_db != null) return _db;
_db = await initDb();
return _db;
}
initDb() async {
io.Directory documentsDirectory = await getApplicationDocumentsDirectory();
String path = join(documentsDirectory.path, "test.db");
// await deleteDatabase(path);
var theDb = await openDatabase(path, version: 1, onCreate: _onCreate);
return theDb;
}
killDb() async{
io.Directory documentsDirectory = await getApplicationDocumentsDirectory();
String path = join(documentsDirectory.path, "test.db");
await deleteDatabase(path);
//initDb();
}
void _onCreate(Database db, int version) async {
// When creating the db, create the table
await db.execute(
"CREATE TABLE Employee(title TEXT, nid TEXT PRIMARY KEY, img TEXT,created TEXT, uid TEXT, totalcount TEXT, pageno INTEGER )");
print("Created tables");
}
readdb() async{
var dbClient = await db;
return await dbClient.rawQuery('SELECT * FROM Employee');
// return dbClient.transaction((txn) async {
// return await txn.rawDelete('SELECT * FROM Employee WHERE lastname = ?', ['48670']);
// });
}
cleardb() async{
var dbClient = await db;
return dbClient.transaction((txn) async {
return await txn.rawDelete('DELETE FROM Employee WHERE firstname = ?', ['test']);
});
}
countItems() async{
var dbClient = await db;
var count = Sqflite.firstIntValue(await dbClient.rawQuery('SELECT COUNT(*) FROM Employee'));
return count;
}
void saveArticle(ArticleslistData article) async {
var dbClient = await db;
await dbClient.transaction((txn) async {
return await txn.rawInsert(
'INSERT INTO Employee(title, nid, img, created, uid, totalcount, pageno ) VALUES(' +
'\'' +
article.title +
'\'' +
',' +
'\'' +
article.nid +
'\'' +
',' +
'\'' +
article.img +
'\'' +
',' +
'\'' +
article.created +
'\'' +
',' +
'\'' +
article.uid +
'\'' +
',' +
'\'' +
article.totalcount +
'\'' +
',' +
'\'' +
article.pageno.toString() +
'\'' +
')');
});
}
Future<List<ArticleslistData>> getArticles() async {
var dbClient = await db;
List<Map> list = await dbClient.rawQuery('SELECT * FROM Employee ORDER BY nid DESC;');
List<ArticleslistData> articles = new List();
for (int i = 0; i < list.length; i++) {
articles.add(new ArticleslistData(list[i]["title"], list[i]["nid"], list[i]["img"], list[i]["created"], list[i]['uid'],list[i]['totalcount'], list[i]['pageno']));
}
return articles;
}
}
答案 0 :(得分：0)
您万事大吉，但需要setState（）告诉flutter重建UI。
如果您不使用状态管理解决方案，请执行此操作。
然后转换为无状态小部件。
onRefresh: () {
SetState() {
fetchEmployeesFromDatabase();
}
}