I am very new to Flutter, and stuck at the following problem:
My function to get a list of books using googleapis:
Future cercaLibri(String ricerca) async {
final String dominio = 'www.googleapis.com';
final String percorso = '/books/v1/volumes';
Map<String, dynamic> parametri = {'q': ricerca};
final Uri url = Uri.https(dominio, percorso, parametri);
print('hello');
http.get(url).then((res) {
final resJson = json.decode(res.body);
final libriMap = resJson['items'];
libri = libriMap.map<Libro>((value) => Libro.fromMap(value)).toList();
setState(() {
libri = libri;
risultato = res.body;
});
});
setState(() {
risultato = "Caricamento in corso";
});
}
for all files see stackblitz
In pubspec.yaml I have
http: ^0.13.4
It seems to me that the get method is not being called, or maybe the call is pending
Sorry the code isn't in English
try adding "http" or "https" to dominio, like:
final String dominio = "http://www.googleapis.com"
or
final String dominio = "https://www.googleapis.com"
I solved the problem
call effect it works
but it fails 'immagineCopertina' which sometimes returns null
I added a control in Image.newtork by putting a dummy url if 'immagineCopertina' is null
Related
My goal is to do a simple BitcoinApp. I am trying to get a method that is in the MyHomePageState class to call a method that I have in another class. When I compile and click on the button to give me the bitcoin info of USD I get the error of setState() callback argument returned to Future. Any advice or alternative that you can suggest me? I'm new to Flutter and adjusting.Here is my code:
///This piece of code is located in MyHomePageState Class
BitcoinCurrency _bitcoin = BitcoinCurrency();
void _getUSDBitcoin(){
setState(() async{
_bitcoin.usdBitcoin();
});
}
///This is the class I have outside of MyHomePageState Class.
class BitcoinCurrency {
///Variables we want for the information
String _disclaimer = "N/A";
String _time = "N/A";
String _currencyBitcoin = "N/A";
///Getters for our variables
get disclaimer => _disclaimer;
get time => _time;
get currencyBitcoin => _currencyBitcoin;
///Methods()
void usdBitcoin() async{
var url = Uri.https('api.coindesk.com', '/v1/bpi/currentprice.json');
var response = await http.get(url);
var httpBody = response.body;
var decoded = json.decode(httpBody);
_disclaimer = decoded['disclaimer'];
_time = decoded['time']['updated'];
_currencyBitcoin = decoded['bpi']['USD']['rate'];
}
}
You can convert usdBitcoin void method to Future<void>
Future<void>? usdBitcoin() async{
var url = Uri.https('api.coindesk.com', '/v1/bpi/currentprice.json');
var response = await http.get(url);
var httpBody = response.body;
var decoded = json.decode(httpBody);
_disclaimer = decoded['disclaimer'];
_time = decoded['time']['updated'];
_currencyBitcoin = decoded['bpi']['USD']['rate'];
}
And call setState like
usdBitcoin().then((value) => setState(() {}));
setState can't be an async function. usdBitcoin has to be a Future method, so you have to call it before the setState starts.
usdBitcoin method:
Future usdBitcoin() async{
var url = Uri.https('api.coindesk.com', '/v1/bpi/currentprice.json');
var response = await http.get(url);
var httpBody = response.body;
var decoded = json.decode(httpBody);
_disclaimer = decoded['disclaimer'];
_time = decoded['time']['updated'];
_currencyBitcoin = decoded['bpi']['USD']['rate'];
}
In initState:
usdBitcoin().then(
(value) => setState(
() {
},
),
)
I'm having issues with the return type of this HTTP request, I need to return Future<List> but the map is returning a List<Future>. I don't know how to get the CustomerInfo without it being a future and I don't know how to return it any other way.
if (response.statusCode == 200) {
Iterable l = json.decode(response.body);
final data = List.from(l.map((model) async {
final name = model['UserName'];
final id = model['UserICode'];
return {name, id};
}));
final users = data.map<CustomerInfo>((e) async {return await getFaxinfo(e.id, e.name);});
return users;
} else {
throw 'err';
}
}
Future<CustomerInfo> getFaxinfo(
String id,
String name,
) async {
final baseUrl = 'localhost';
final int port = 3003;
final accountsPath = '/accounts';
final accountsFaxInfoPath = '$accountsPath/fax-info';
final Map<String, dynamic> queryParam = {'id': id};
final uri = Uri(
scheme: 'http',
path: accountsFaxInfoPath,
host: baseUrl,
queryParameters: queryParam);
final response = await http.get(uri);
return CustomerInfo(sent: 200, received: 300, name: 'Test');
}
The problem is that an async function always returns a Future no matter if you call await inside it or not. To fix it a good approach is to use list comprehension. A simple for loop also would do.
Instead of those 2 maps that result in List<Future>:
final data = List.from(l.map((model) async {
final name = model['UserName'];
final id = model['UserICode'];
return {name, id};
}));
final users = data.map<CustomerInfo>((e) async {return await getFaxinfo(e.id, e.name);});
Do the following with list comprehension:
final users = [
for (final model in l)
await getFaxinfo(model['UserICode'], model['UserName'])
];
Now if you want to make the HTTP calls in parallel it's possible to do a Future.wait() in a List<Future> to get the result as List<CustomerInfo>. Something like the following:
final users = await Future.wait(l.map((model) async =>
await getFaxinfo(model['UserICode'], model['UserName'])));
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()));
I try to use compute in Flutter. Here I try to pass multiple parameters inside a Map. But the code in my function myFunction does not work. I get no errors or something else. My code seems to be ignored. Do you find an error here?
Compute function:
Map map = Map();
map['resultList'] = resultList;
map['_getImageFileFromAssets'] = _getImageFileFromAssets;
map["picturesData"] = picturesData;
map["albumID"] = albumID;
await compute(myFunction, map);
Calls the following function:
Future<bool> myFunction(map) async {
var resultList = map["resultList"];
var _getImageFileFromAssets = map["_getImageFileFromAssets"];
var picturesData = map["picturesData"];
var albumID = map["albumID"];
print("Starten");
for (var i = 0; i < resultList.length; i++) {
print(i);
File imageFile = await _getImageFileFromAssets(resultList[i]);
final appDir = await syspath.getApplicationDocumentsDirectory();
final fileName = path.basename(imageFile.path);
final savedImage =
await File(imageFile.path).copy('${appDir.path}/$fileName');
// Creating thumbnails
final thumb = image.decodeImage(await File(savedImage.path).readAsBytes());
final thumbImage = image.copyResize(thumb, width: 500);
new File('${appDir.path}/$fileName-thumb-500.jpg')
.writeAsBytes(image.encodeJpg(thumbImage));
final finalThumbImage = File('${appDir.path}/$fileName-thumb-500.jpg');
picturesData.add(Picture(
album: albumID,
path: savedImage.path,
thumbPath: finalThumbImage.path,
timestamp: Timestamp.now()));
}
return true;
}
Ok, some code - I put this in dartpad.dev:
import 'package:flutter/foundation.dart';
void main() {
Map map = Map();
compute(myFunction, map).then((result) => print(result));
}
Future<bool> myFunction(Map map) async {
print("Starten");
// fake long process
await Future.delayed(Duration(seconds: 5));
return true;
}
and get this as a console result:
Starten
true
Also: is there a reason you need the "map" parameter in your function to be dynamic? If not, I'd declare it as type Map (like I did now).
I am using this package to retrieve device's contacts. The lib retrieve 427 contacts and I want to loop the whole list so that I can create another list and send it to the back-end. The problem is looping does not work this the function return before looping is completed.
Here the function I use:
Future<QueryResult> uploadContacts() async {
final List<Contact> rawContacts =
(await ContactsService.getContacts(withThumbnails: false)).toList();
List<ContactInput> contactsListInput;
print('contactsListInput length: ${rawContacts.length}');
rawContacts.forEach((contact) {
print('contact: $contact'); //PRINTED JUST ONCE
//Contact can have more than 1 number. We need them all
contact.phones.forEach((phone) {
final contactInput =
ContactInput(name: contact.displayName, phone: phone.value);
contactsListInput.add(contactInput);
});
});
print('contactsListInput length: ${contactsListInput.length}'); //NEVER PRINT ANYTHING
final ContactsListInput input =
ContactsListInput(contacts: contactsListInput);
final MutationOptions _options = MutationOptions(
document: SyncContactsMutation().document,
variables: SyncContactsArguments(input: input).toJson());
return client.mutate(_options);
}
I have also tried using for loop and the same thing happened.
for (int i = 0; i < rawContacts.length; i++) {
final contact = rawContacts[i];
final contactInput =
ContactInput(name: contact.displayName, phone: contact.phones.first.value);
contactsListInput.add(contactInput);
}
print('contactsListInput length: ${contactsListInput.length}'); //NEVER CALLED
And I also tried Future.forEach
await Future.forEach(rawContacts, (contact) async {
print('contact: $contact');
//Since contact can have more than one number we loop them too.
await Future.forEach(contact.phones, (phone) async {
final contactInput =
ContactInput(name: contact.displayName, phone: phone.value);
contactsListInput.add(contactInput);
});
});
How to fix this? Any help will be much appreciated.
I have fixed it as
Future<QueryResult> uploadContacts() async {
final Iterable<Contact> rawContacts =
(await ContactsService.getContacts(withThumbnails: false));
final Iterable<ContactInput> contacts = rawContacts.expand((contact) => contact.phones.map(
(phone) =>
ContactInput(name: contact.displayName, phone: phone.value)));
final input = ContactsListInput(contacts: contacts);
final MutationOptions _options = MutationOptions(
document: SyncContactsMutation().document,
variables: SyncContactsArguments(input: input).toJson());
return client.mutate(_options);
}
Credit goes to #pskink and #loganrussell48
You should use it as a dynamic type object. Try something like this:
(event.snapshot.value as dynamic).forEach()
Try and see if it works.