我正在尝试为 DropDownButton 创建一个自定义小部件。看起来效果很好。当我在控制台打印更改后的值时， onChanged() 函数也可以工作。 但是，我无法在 Onchanged() 函数之后查看框中的文本。
有人可以让我知道同样的事情可能有什么问题吗？ 我的小部件代码如下：
import 'package:flutter/material.dart';
import 'package:shared_preferences/shared_preferences.dart';
class InputScreen2 extends StatefulWidget {
final List<double> sizes;
const InputScreen2({Key? key, required this.sizes}) : super(key: key);
@override
State<InputScreen2> createState() => _InputScreen2State();
}
class _InputScreen2State extends State<InputScreen2> {
Future? future;
double screenwd = 0, screenht = 0;
List<String> listsex = ['Male', 'Female'];
String? sex;
@override
void initState() {
// TODO: implement initState
future = _future();
super.initState();
}
Future<int> _future() async {
SharedPreferences prefs = await SharedPreferences.getInstance();
screenwd = widget.sizes[0];
screenht = widget.sizes[1];
return 0;
}
@override
Widget build(BuildContext context) {
return Scaffold(
backgroundColor: Colors.orange,
body: FutureBuilder(
future: future,
builder: (context, snapshot) {
if (snapshot.hasError) {
return Center(
child: Text(
'Data Error...Please try again',
style: Theme.of(context).textTheme.titleSmall,
));
} else if (snapshot.connectionState == ConnectionState.waiting) {
return Text(
'Waiting',
style: Theme.of(context).textTheme.titleSmall,
);
} else if (!snapshot.hasData) {
return Text(
'No Data',
style: Theme.of(context).textTheme.titleSmall,
);
} else if (snapshot.hasData) {
//Block I====================================================
return SafeArea(
child: Center(
child: Container(
padding: const EdgeInsets.all(20.0),
decoration: BoxDecoration(
border: Border.all(width: 2.0), color: Colors.blue),
width: screenwd * .8,
height: screenht * .75,
child: SingleChildScrollView(
child: Column(
children: [
Row(
mainAxisAlignment: MainAxisAlignment.start,
children: [
const Text(
'Personal Details',
),
const SizedBox(
width: 23,
),
dropDownMenu('Sex', sex, listsex),
],
),
],
),
),
),
),
);
}
return const Text('No DATA');
}));
}
Widget dropDownMenu(String title, String? inputTxt, List<String> stringList) {
return Container(
margin: const EdgeInsets.only(top: 10.0),
child: Column(
crossAxisAlignment: CrossAxisAlignment.start,
children: [
Text(
title,
),
Container(
width: 80,
height: 35,
decoration: BoxDecoration(
border: Border.all(color: Colors.white, width: 1.0),
borderRadius: const BorderRadius.all(Radius.circular(5.0))),
child: DropdownButton<String>(
value: inputTxt,
dropdownColor: Colors.amber,
items: stringList.map<DropdownMenuItem<String>>((String value) {
return DropdownMenuItem<String>(
value: value,
child: Text(
value,
style: const TextStyle(color: Colors.white),
));
}).toList(),
onChanged: (String? value) {
setState(() {
inputTxt = value!;
});
}),
),
],
),
);
}
}
我在 Dartpad 中尝试了你的代码：你必须用这个替换 dropDownMenu
onChanged onChanged: (String? value) {
setState(() {
sex = value!;
});
}),
我想你只是把
inputTxtsexdropDownMenu中的
inputTxt：只需将其替换为 sex_InputScreen2StateWidget dropDownMenu(String title, List<String> stringList) {
return Container(
margin: const EdgeInsets.only(top: 10.0),
child: Column(
crossAxisAlignment: CrossAxisAlignment.start,
children: [
Text(title),
Container(
width: 80,
height: 35,
decoration: BoxDecoration(
border: Border.all(color: Colors.white, width: 1.0),
borderRadius: const BorderRadius.all(Radius.circular(5.0))),
child: DropdownButton<String>(
value: sex,
dropdownColor: Colors.amber,
items: stringList.map<DropdownMenuItem<String>>((String value) {
return DropdownMenuItem<String>(
value: value,
child: Text(
value,
style: const TextStyle(color: Colors.white),
));
}).toList(),
onChanged: (String? value) {
setState(() {
sex = value!;
});
}),
),
],
),
);
}
我在同一个 Dartpad 中测试了它，它有效。