I have a String List in my shared preferences that's meant to store account numbers which can then be used to make a call from the API:
List<String> accountList = [];
Future _getListData() async {
SharedPreferences myPrefs = await SharedPreferences.getInstance();
for(var i = 0; i < myPrefs.getStringList('accounts').length; i++){
accountList.add(myPrefs.getStringList('accounts')[i]);
}
//prints values from shared preferences
print(accountList);
}
Future<List<dynamic>> fetchData() async {
_getListData();
//prints an empty list
print(accountList);
try {
if (accountList == null) {
var result = await http.get(apiUrl);
List<dynamic> accountInfo = (json.decode(result.body));
return accountInfo;
} else {
List<dynamic> accountInfo = [];
for(var i = 0; i < accountList.length; i++){
var result =
await http.get(apiUrl + "/api/Data/GetCustomer?accntnum=" + accountList[i]);
accountInfo.add(json.decode(result.body));
}
return accountInfo;
}
} catch (e) {
print(e);
}
}
When calling the Future function "fetchData()" from my FutureBuilder in the widget it returns an empty list. However within the scope of the "_getListData()" function it prints the list witht he appropriate values. How can I make it such that "fetchData()" gets the intended list?
Just add an await before _getListData() here:
Future<List<dynamic>> fetchData() async {
await _getListData();
//prints an empty list
print(accountList);
Related
I'm trying to get datas from api and add them a list. But at this moment, I see datas i got but I can't get it out of the function. What should i do?
function
List<dynamic> xxx = [];
#override
void initState() {
super.initState();
Future<List<dynamic>> fetchCompanies(List<dynamic> datas) async {
var response = await Dio().get(CompaniesPath().url);
if (response.statusCode == HttpStatus.ok) {
Map<String, dynamic> company = jsonDecode(response.data);
for (int i = 0; i < company['Data'].length; i++) {
datas.add(company['Data'][i]);
}
//print(datas); //=> I see datas here
} else {
throw Exception();
}
return datas;
}
print(fetchCompanies(xxx));
}
When I run print(fetchCompanies(xxx)); I got "Instance of 'Future<List<dynamic>>'". How can i get data inside fetchCompanies to my xxx list?
You're trying to print future instance of List that's why you got
Instance of Future<List>
You have to wait until function finish executing.
Catch here is you can't call wait in initState() so you have to use .then method
try this:
fetchCompanies(xxx)
.then((result) {
print("result: $result");
});
It should already work fine like it is. But you probably want to call a setState to refresh the page. Try this:
#override
void initState() {
super.initState();
Future<List<dynamic>> fetchCompanies(List<dynamic> datas) async {
var response = await Dio().get(CompaniesPath().url);
if (response.statusCode == HttpStatus.ok) {
Map<String, dynamic> company = jsonDecode(response.data);
for (int i = 0; i < company['Data'].length; i++) {
datas.add(company['Data'][i]);
}
//print(datas); //=> I see datas here
setState(() {}); // added this
} else {
throw Exception();
}
return datas;
}
print(fetchCompanies(xxx));
}
Hello all at first I want to mention that I've tried a lot of solutions here but it didn't work for me.
I bring the list from the database through the following code:
var listCat = [];
Future getdata() async {
apiURL = '***************.php';
var response = await http.post(Uri.parse(apiURL));
var responsebody = jsonDecode(response.body);
if (responsebody.length >0){
for (int i = 0; i < responsebody.length; i++) {
listCat.add(responsebody[i]['name']+ ':' + responsebody[i]['image'].toString());
}
return responsebody;
}else{
}
}
As is obvious in the code above I am trying to get the name and image and this is not a problem right now I want to store this listCat in SharedPreferences until I recall it from all pages of the app
I have the following class to save SharedPreferences:
class APIPreferences {
static SharedPreferences ? _preferences;
static const _keyMuinCat = 'MuinCat';
static Future init() async => _preferences = await SharedPreferences.getInstance();
static Future setMuinCat(String MuinCat) async => await _preferences!.setString(_keyMuinCat, MuinCat);
static String? getMuinCat() => _preferences!.getString(_keyMuinCat);
}
Then I save what I need to save by the following line:
APIPreferences.setMuinCat(listCat.toString());
Then I can bring pre-stored data from any location where I need it through the following code:
CatList = APIPreferences.getMuinCat() ?? '';
I tried to do the following thing now to save the list in the first code above:
var listCat = [];
Future getdata() async {
apiURL = '***************.php';
var response = await http.post(Uri.parse(apiURL));
var responsebody = jsonDecode(response.body);
if (responsebody.length >0){
for (int i = 0; i < responsebody.length; i++) {
listCat.add(responsebody[i]['name']+ ':' + responsebody[i]['image'].toString());
APIPreferences.setMuinCat(listCat.toString());
}
return responsebody;
}else{
}
}
But it didn't work. I don't really know how to deal with it.
How can I save it and then bring it to use with ListView.
instead of:
_preferences!.setString(_keyMuinCat, "some string");
use:
_preferences!.setStringList(_keyMuinCat, ["some", "strings", "in", "list"]);
So in your code, the setMuinCat method needs to be:
static Future setMuinCat(List<String> muinCat) async => await _preferences!.setStringList(_keyMuinCat, muinCat);
and then you call it like this:
APIPreferences.setMuinCat((listCat as List).map((v) => v.toString()).toList());
To save the list in shared preferences you need to pass as jsonEncode(yourList data) and when you will fecth the shared list you will again jsonDecode(your list)
await prefs.setString('YOUR KEY', json.encode(YOURMAP()));
The Problem is here that I can't find a list of lists and fetch complete information of other lists from API in flutter using Dio.
void fetchAllIndicatorsList(int ModuleId) async {
try {
isLoading(true);
var indicatorslist = await DioClient.fetchAllIndicators(ModuleId);
if (indicatorslist != null) {
Indicatorslist.clear();
first list ==> IndicatorsChecklist.clear();
Indicatorslist.value = indicatorslist;
for(var i=0; Indicatorslist.length>0; i++){
==> second list IndicatorsChecklist.assignAll(Indicatorslist[i].indicators!.length.obs.toJson());
}
}
} finally {
isLoading(false);
}
}enter link description here
Check out my example of getting lists in Dio
Future getCourses() async {
String endPoint = 'api/courses';
final api = service.getApiClient();
try {
final result = await api!.get(endPoint);
final rawList = result.data["data"] as List;
final list = rawList.map((e) => Course.fromJson(e)).toList();
return list;
} on DioError catch (error) {
return error.response!.data;
}
}
I have a Future which returns a map. I then need to use the values of that map to await another future and then return the entire result at the end. The problem is that dart can't await async Map.forEach() methods (see this: https://stackoverflow.com/a/42467822/15782390).
Here is my code:
the debug console shows that the items printed are in the following order:
flutter: getting journal entries
flutter: about to loop through pictures
flutter: getting picture
flutter: returning entries
flutter: [[....]] (Uint8List)
Future<List<JournalEntryData>> getJournalEntries() async {
List<JournalEntryData> entries = [];
print('getting journal entries');
EncryptService encryptService = EncryptService(uid);
await journal.get().then((document) {
Map data = (document.data() as Map);
print('about to loop through pictures');
data.forEach((key, value) async {
print('getting picture');
dynamic pictures = await StorageService(uid).getPictures(key);
print('done getting image');
entries.add(JournalEntryData(
date: key,
entryText: encryptService.decrypt(value['entryText']),
feeling: value['feeling'],
pictures: pictures,
));
});
});
print('returning entries');
return entries;
}
Future getPictures(String entryID) async {
try {
final ref = storage.ref(uid).child(entryID);
List<Uint8List> pictures = [];
await ref.listAll().then((result) async {
for (var picReference in result.items) {
Uint8List? pic = await ref.child(picReference.name).getData();
if (pic == null) {
// TODO make no picture found picture
var url = Uri.parse(
'https://www.salonlfc.com/wp-content/uploads/2018/01/image-not-found-scaled-1150x647.png');
var response = await http.get(url);
pic = response.bodyBytes;
}
pictures.add(pic);
}
});
return pictures;
} catch (e) {
print(e.toString());
return e;
}
}
It's quite annoying to have to use for-loops when you need async behaviour, specially on Maps, because as the other answer shows, that requires you to iterate over entries and then take the key and value out of it like this:
for (final mapEntry in data.entries) {
final key = mapEntry.key;
final value = mapEntry.value;
...
}
Instead of that, you can write a utility extension that does the work for you:
extension AsyncMap<K, V> on Map<K, V> {
Future<void> forEachAsync(FutureOr<void> Function(K, V) fun) async {
for (var value in entries) {
final k = value.key;
final v = value.value;
await fun(k, v);
}
}
}
Then, you can use that like this:
await data.forEachAsync((key, value) async {
...
});
Much better.
Don't mix the use of then and await since it get rather confusing and things are no longer being executed as you think.
Also, the use of forEach method should really not be used for complicated logic like what you are doing. Instead, use the for-each loop. I have tried rewrite getJournalEntries here:
Future<List<JournalEntryData>> getJournalEntries() async {
List<JournalEntryData> entries = [];
print('getting journal entries');
EncryptService encryptService = EncryptService(uid);
final document = await journal.get();
Map data = (document.data() as Map);
print('about to loop through pictures');
for (final mapEntry in data.entries) {
final key = mapEntry.key;
final value = mapEntry.value;
print('getting picture');
dynamic pictures = await StorageService(uid).getPictures(key);
print('done getting image');
entries.add(JournalEntryData(
date: key,
entryText: encryptService.decrypt(value['entryText']),
feeling: value['feeling'],
pictures: pictures,
));
}
print('returning entries');
return entries;
}
And getPictures here. I have only removed the use of then here.
Future getPictures(String entryID) async {
try {
final ref = storage.ref(uid).child(entryID);
List<Uint8List> pictures = [];
final result = await ref.listAll();
for (var picReference in result.items) {
Uint8List? pic = await ref.child(picReference.name).getData();
if (pic == null) {
// TODO make no picture found picture
var url = Uri.parse(
'https://www.salonlfc.com/wp-content/uploads/2018/01/image-not-found-scaled-1150x647.png');
var response = await http.get(url);
pic = response.bodyBytes;
}
pictures.add(pic);
}
return pictures;
} catch (e) {
print(e.toString());
return e;
}
}
i have been trying to get all my data from a sqflite database, when i try to get a single data, this works totally fine:
Future<dynamic> getUser() async {
final db = await database;
var res = await db.query("files");
if (res.length == 0) {
return null;
} else {
var resMap = res[0];
return resMap;
}
}
but when i try to get all data using a for loop like the example below, i get an error
Future<dynamic> getUser() async {
final db = await database;
var res = await db.query("files");
var resMap;
var count = res.length;
if (count != 0) {
for (int i = 0; i < count; i++) {
resMap.add(res[i]);
}
}
return resMap;
}
the error says:
The method 'forEach' was called on null.
Receiver: null
Tried calling: forEach(Closure: (dynamic, dynamic) => Null)
i understand that it says that I've got no data,
and i also tried to remove the if statement, but still no luck!
change this method:
EDIT
Future<List<Map>> getUser() async {
final db = await database;
var res = await db.query("files");
List<Map> resMap = [];
if (res != null res.length > 0) {
for (int i = 0; i < count; i++) {
resMap.add(res[i]);
}
return resMap;
} else
{
return null;
}
}
try this in you widget
List<Map> newUser = [];
#override
void initState() {
super.initState();
getUser();
}
getUser() async {
final _userData = await DBProvider.db.getUser();
if(_userData != null ){
setState(() {
newUser = _userData;
});
} else{
setState(() {
newUser =[];
});
}
}