[英]Flutter - StatefulBuilder - The declaration setState isn't referenced
I'm writing an alertDialog where the user can type a name.我正在编写一个警报对话框,用户可以在其中输入名称。 The alertDialog has a "OK" button and a "Annulla" button.
alertDialog 有一个“OK”按钮和一个“Annulla”按钮。 I want the "OK" button to be disabled while the textField is empty, and then enabled when the user types something.
我希望在 textField 为空时禁用“确定”按钮,然后在用户键入内容时启用。
I'm using a statefulBuilder as recommended by some answers here on StackOverflow, but clearly my implementation is not working.我正在使用 StackOverflow 上的一些答案所推荐的 statefulBuilder,但显然我的实现不起作用。
// Function to display a dialog to insert a new item to the list
Future<void> _displayItemAddDialog(BuildContext context, provider) async {
String itemName;
// clear the textField and add the item to the list
Future<void> onOKPressed() {
_textFieldController.clear();
Navigator.pop(context);
provider.addItem(itemName);
}
showDialog(
context: context,
builder: (context) {
return StatefulBuilder(
builder: (BuildContext context, StateSetter setState) {
// used to check if to enable the OK button
bool okButtonEnabled = false;
return AlertDialog(
title: Text('Inserisci Nome Oggetto'),
content: TextField(
onChanged: (value) {
itemName = value;
print(value);
// if the TextField is not empty then enable the button
if (value != "") {
// not working :(
setState() => okButtonEnabled = true;
}
},
controller: _textFieldController,
decoration: InputDecoration(hintText: 'Nome'),
),
actions: <Widget>[
TextButton(
onPressed: () {
_textFieldController.clear();
Navigator.pop(context);
},
child: Text('Annulla'),
),
TextButton(
// if button enabled then I change the assigned function
onPressed: okButtonEnabled ? onOKPressed : null,
child: Text('OK')),
],
);
});
});
}
You should move your okButtonEnabled
outside StatefulBuilder, so right above it.你应该把你的
okButtonEnabled
移到 StatefulBuilder 之外,就在它上面。
showDialog(
context: context,
builder: (context) {
// Move okButtonEnabled here
bool okButtonEnabled = false;
return StatefulBuilder(
builder: (BuildContext context, StateSetter setState) {
return AlertDialog(
title: Text('Inserisci Nome Oggetto'),
content: TextField(
onChanged: (value) {
itemName = value;
print(value);
// if the TextField is not empty then enable the button
if (value != "") {
setState(() => okButtonEnabled = true);
}
},
controller: _textFieldController,
decoration: InputDecoration(hintText: 'Nome'),
),
actions: <Widget>[
TextButton(
onPressed: () {
_textFieldController.clear();
Navigator.pop(context);
},
child: Text('Annulla'),
),
TextButton(
// if button enabled then I change the assigned function
onPressed: okButtonEnabled ? onOKPressed : null,
child: Text('OK')),
],
);
},
);
},
);
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