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(
() {
},
),
)
Related
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 am getting some data from API in flutter. I am trying to decode the data using json.decode() but this decode function gives me the following error:
Closure: () => String from Function 'toString'
Here's my code:
Future<Product> createOrder() async {
var client = new http.Client();
var productModel = null;
try {
var response = await client
.get(Uri.https('butterbasket.onrender.com', Strings.createOrderUrl));
if (response.statusCode == 200) {
var body = response.body;
print("Body: $body");
var jsonMap = json.decode(body);
var productModel = Product.fromJson(jsonMap);
}
} catch (e) {
print("Exception: ${e.toString}");
}
return productModel;
}
Here is the Error Debug Console:
You are running into issues because the data you are loading in is an array, but the model is an object. You'll need to do something like the following:
final List jsonProducts = json.decode(body)
final List<Product> products =
jsonProducts.map((jsonProduct) => Product.fromJson(jsonProduct)).toList();
and then if you only need the first item you can do:
final Product product = products[0]
But don't forget to check if the array is big enough.
Your Future function must return an optional Product?, otherwise your future will never find a result as you are declaring it inside the function.
Instead of:
Future<Product> createOrder() async {}
Use:
Future<Product?> createOrder() async {}
Finally your async snapshot and FutureBuilder type should be of type <Product?>.
I have a scenario where the following function is called again and again whenever the user hits the "Load More" button.
The problem I'm facing is, that it replaces previously loaded data with a new one. Instead, it should add to the bottom of the Listview.Builder
Future fetchData() async{
var url = "url_goes_here";
final response = await http.get(url);
if (response.statusCode == 200) {
var resBody = jsonDecode(response.body);
var data = resBody['data'] as List;
if (data.isNotEmpty) {
setState(() {
listVariable = data
.map<ModelClass>((json) => ModelClass.fromJson(json))
.toList();
});
}
}
}
List<ModelClass> listVariable =List<ModelClass>(); //describe the object that way.
--------and---------
data.map<ModelClass>((json) {
listVariable.add(ModelClass.fromJson(jsonn));
} )).toList();
You should add received data to your listVariable, not assign a new value. Try this code:
final listVariable = <ModelClass>[];
...
Future fetchData() async {
var url = "url_goes_here";
final response = await http.get(url);
if (response.statusCode == 200) {
var resBody = jsonDecode(response.body);
var data = resBody['data'] as List;
if (data.isNotEmpty) {
final list = data.map<ModelClass>((json) => ModelClass.fromJson(json));
setState(() {
listVariable.addAll(list); // HERE: addAll() instead of assignment
});
}
}
}
I was able to figure out answer myself.
setState(() {
listVariable.addAll(data
.map<ModelClass>((json) => ModelClass.fromJson(json))
.toList();
}));
#Mol0ko and #hasan karaman both are right but #Mol0ko
Makes better sense when you have a set of data to addAll to existing data.
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}/$fileName-thumb-500.jpg');
picturesData.add(Picture(
album: albumID,
path: savedImage.path,
thumbPath: finalThumbImage.path,
timestamp: Timestamp.now()));
}
return true;
}
Ok, some code - I put this in dartpad.dev:
import 'package:flutter/foundation.dart';
void main() {
Map map = Map();
compute(myFunction, map).then((result) => print(result));
}
Future<bool> myFunction(Map map) async {
print("Starten");
// fake long process
await Future.delayed(Duration(seconds: 5));
return true;
}
and get this as a console result:
Starten
true
Also: is there a reason you need the "map" parameter in your function to be dynamic? If not, I'd declare it as type Map (like I did now).
Whenever trying to call future data and trying converting to List, it returns the error
type 'Future' is not a subtype of type 'List'
Tried type-casting, but no help
On HomePage.dart
final getPost = NetworkFile().getPosts();
List posts;
void getPostsList() {
setState(() {
var res = getPost;
posts = res as List<dynamic>;
print(posts);
});
}
On Network.dart
class NetworkFile{
Future<dynamic> getPosts() async {
var response = await http.get('$kBlogURL' + 'posts?_embed');
Iterable resBody = await jsonDecode(response.body.toString());
return resBody;
}
}
You are decoding the response and its a List of type dynamic. There are few method to handle it. You can create a simple PODO class and cast/mapped to it. Or just do like below:
List posts = [];
void getPostsList() async {
final fetchedPosts = await NetworkFile().getPosts();
setState(() {
posts = fetchedPosts;
});
print(posts);
}
Here is a nice article about PODO.
final getPost = NetworkFile().getPosts();
Map posts;
void getPostsList() async {
var res = await getPost;
setState(() {
posts = res as Map<String, dynamic>;
print(posts);
});
}
class NetworkFile {
Future<dynamic> getPosts() async {
var response = await http.get('https://onetechstop.net/wp-json/wp/v2');
var resBody = await jsonDecode(response.body.toString());
return resBody;
}
}