Flutter: How to change variables through TextFormField in a AlertDialog? - flutter

Question

I want to implement a function as following:
There is a button named 自定义. In this page, there is a variable named money. When I click the button, an AlertDialog with a TextFormField inside will occur. I hope that after inputting a number X into the TextFormField and clicking button ok to exit the AlertDialog, money would be changed to X. I have used onSaved to save the variable, and used _formkey.currentState.save(), but money didn't change. What's wrong with my codes? Here are my codes:
void _showMessageDialog() {
//int addMoney = 0;
showDialog(
context: context,
builder: (BuildContext context) {
// return object of type Dialog
return AlertDialog(
key: _formKey,
title: new Text('INPUT'),
content: TextFormField(
maxLines: 1,
keyboardType: TextInputType.emailAddress,
autofocus: false,
style: TextStyle(fontSize: 15),
decoration: new InputDecoration(
border: InputBorder.none,
hintText: 'input',
),
onSaved: (value) {
money = int.parse(value?.trim() ?? '0') as double;
print(money);
}
),
actions: <Widget>[
new TextButton(
key: _formKey,
child: new Text("ok"),
onPressed: () {
_formKey.currentState?.save();
Navigator.of(context).pop();
},
),
],
);
},
);
}
Here are the codes relative to the button 自定义
OutlinedButton(
style: OutlinedButton.styleFrom(
side: BorderSide(
width: 1,
color: Colors.blueAccent
)
),
onPressed: () {
// Navigator.of(context).push(
// _showMessageDialog()
// );
_showMessageDialog();
},
child: Text(
"自定义",
style: TextStyle(
fontSize: 20,
fontWeight: FontWeight.w700,
color: Colors.blueAccent
),
),
),
I know maybe I have made a big mistake, but it is my first Flutter project. Thanks for your advices.

Answer 1

I would use ValueNotifier for this. But first you need to add a controller to your TextFormField so you can get the text user typed in.
//initialize it
final myController = TextEditingController();
TextFormField(
controller: myController, //pass it to the TextFormField
),
TextButton(
child: new Text("ok"),
onPressed: () {
String input = myController.text; //this is how you get the text input
_formKey.currentState?.save();
Navigator.of(context).pop();
},
),
As I said you also need to initialize ValueNotifier and pass it to _showMessageDialog
ValueNotifier<int> money = ValueNotifier(0);
_showMessageDialog(money); //and pass it to your function
void _showMessageDialog(ValueNotifier<int> money) {
TextButton(
child: new Text("ok"),
onPressed: () {
String input = myController.text; //this is how you get the text input
money.value = int.parse(input); //and then update your money variable
_formKey.currentState?.save();
Navigator.of(context).pop();
},
),
}