[英]setState is not working inside the floating action button and not able to render the ui in flutter?
[英]setState is not working with DropDown Button in Flutter
當我從下拉列表中選擇數量時,我正在根據數量計算總量,但總量Textformfield
保持不變,當我調試代碼時,我在setState
方法中獲得更新的數量,但沒有反映在 UI 上,我也是從它正在工作的方法中的另一種方法更新總數。
class _ProductDetailsPageState extends State<ProductDetailsPage> {
List _quantity = ["1", "2", "3", "4", "5"];
List<DropdownMenuItem<String>> _dropDownQuantity;
String _currentQuantity;
String _productprice;
double _taxrateamt;
double _taxper = 0.0;
String _producttotal;
int _productqty;
double _discount = 3.0;
String _productname;
List<DropdownMenuItem<String>> getDropDownQuantity() {
List<DropdownMenuItem<String>> items = new List();
for (String city in _quantity) {
items.add(new DropdownMenuItem(
value: city,
child: new Text(
city,
style:
TextStyle(color: MyColors.colorPrimary, fontFamily: 'semibold'),
)));
}
return items;
}
@override
void initState() {
super.initState();
_dropDownQuantity = getDropDownQuantity();
_currentQuantity = _dropDownQuantity[0].value;
}
Container rateAndTotal( String value) {
return Container(
child: Column(
children: <Widget>[
Row(
mainAxisAlignment: MainAxisAlignment.spaceBetween,
children: <Widget>[
Expanded(
flex: 1,
child: Container(
child: TextFormField(
style: TextStyle(
fontFamily: 'medium', color: MyColors.colorPrimaryDark),
keyboardType: TextInputType.number,
enabled: false,
textInputAction: TextInputAction.done,
initialValue: '${value}',
decoration: InputDecoration(
border: InputBorder.none, hintText: '$value'),),),),],),],),);}
Container quantity() {
return Container(
child: Column(
children: <Widget>[
Row(
mainAxisAlignment: MainAxisAlignment.spaceBetween,
children: <Widget>[
Expanded(
flex:1,
child: Container(
child: DropdownButtonHideUnderline(
child: DropdownButton(
value: _currentQuantity,
items: _dropDownQuantity,
onChanged: changedDropDownQuantity,),)),),],),],),);}
@override
Widget build(BuildContext context) {
MediaQueryData queryData;
queryData = MediaQuery.of(context);
double width = queryData.size.width;
double height = queryData.size.height;
return new Container(
height: double.infinity,
decoration: BoxDecoration(color: Colors.grey[200]),
child: SingleChildScrollView(
child: Container(
padding: EdgeInsets.all(height * 0.020),
child: Column(
children: <Widget>[
quantity(),
rateAndTotal( '${_productprice}'),
],
),
),
),
);
}
void changedDropDownQuantity(String selected_quantity) {
setState(() {
_currentQuantity = selected_quantity;
// _producttotal=getProductTotal(_productprice,_currentQuantity);
});
setState(() {
_producttotal=getProductTotal(_productprice,_currentQuantity);
});
}
String getProductTotal(String productprice, String _currentQuantity) {
try {
double sprice = 0.0;
double total = double.parse(productprice);
double taxrate = _taxrateamt;
double qty = double.parse(_currentQuantity);
return _producttotal =
(((total + taxrate + sprice) - _discount) * qty).toString();
} catch (e) {
debugPrint('PRODUCT TOTAl EXC.:--${e}');
return _producttotal = productprice;
}
}
}
要解決此問題,請替換 TextFormField 中的以下行:
initialValue: '$value',
和:
controller: TextEditingController(text: value),
或者更好:
// Define a controller in the State
class _ProductDetailsPageState extends State<ProductDetailsPage> {
TextEditingController _controller = TextEditingController(text: value);
...
// Then bind that controller to your TextFormField, replacing initialValue
child: TextFormField(
controller: _controller,
...
// Then change the .text property of that controller when you want it to update
setState(() => _controller.text = value);
initialValue
僅用於設置第一次初始化State
時TextFormField
第一個值是什么,並且State
通過重建保留,因此覆蓋它永遠不會導致文本更改。
重寫TextEditingController
每次完全或定義TextEditingController
和改變.text
屬性將正確地傳遞改變了State
的領域,並更新你的價值。
另一種情況; 如果在彈出窗口中使用下拉按鈕,則需要使用 StatefulBuilder。 這是參考; 如何在 Flutter 中刷新 AlertDialog?
聲明:本站的技術帖子網頁,遵循CC BY-SA 4.0協議,如果您需要轉載,請注明本站網址或者原文地址。任何問題請咨詢:yoyou2525@163.com.