Flutter Save JSON Array to SharedPreferences - arrays

Question

How to save JSON array into SharedPreferences?
I've tried some code like this below, but i got some error :
[ERROR:flutter/lib/ui/ui_dart_state.cc(148)] Unhandled Exception: type
'Text' is not a subtype of type 'String'
for (var x = 0; x < dynamicwidget.length - 1; x++) {
_listOrder={
"id_product": dataJSON[x]["product_id"],
"order_count": dynamicwidget[x].controller.text,
};
}
String json = jsonEncode(_listOrder);
SharedPreferences prefs = await SharedPreferences.getInstance();
prefs.setString(categoryname, json);

Answer 1

I would recommend you to use something like this (local storage implementation) which is made for saving and loading JSON.
From the code snippet itself i can't tell you exactly what is causing this exception but basically everywhere a String is beeing expected but you provided an actual Text widget. It could be the categoryname variable. What kind of controller do you get from your dynamicWidget instance? Are you sure controller.text returns a String?
Another note: you are re-assigning _listOrder with every for loop instead of adding information. You have to use an empty array which will be filled with every loop.

Answer 2

Thanks all, for contributing this question.
I've solved this question and makes some change.
_listOrder.clear();
for (var x = 0; x < dynamicwidget.length; x++) {
int jml = int.parse(dynamicwidget[x].controller.text == ""? "0": dynamicwidget[x].controller.text);
if (jml > 0) {
_listOrder.add({
"id_product": dataJSON[x]["product_id"],
"order_count": dynamicwidget[x].controller.text,
});
}
}
if (_listOrder.length > 0) {
SharedPreferences prefs = await SharedPreferences.getInstance();
Map<String, dynamic> _collOrder = Map<String, dynamic>();
String sessjson = prefs.getString("orderlist");
if (sessjson != null) {
_collOrder = json.decode(sessjson);
_collOrder.remove(categoryname);
}
_collOrder[categoryname] = _listOrder;
prefs.setString("orderlist", json.encode(_collOrder));
}