flutter - 如何在颤动中按下按钮时更改价格
问题描述
设想
我有一个虚拟图像,图像下方有价格,价格下方有三个小部件 两个小部件是按钮 (+) 和 (-),一个小部件是 Text('1'),它是一个数量。
问题
当我单击按钮时,它会增加和减少数字,但我如何根据数量更改价格(如果数量为 2,则价格必须翻倍)
class Quantities extends StatefulWidget {
final productprice;
final productimage;
Quantities({this.productprice, this.productimage});
@override
_QuantitiesState createState() => _QuantitiesState(productprice,productimage);
}
class _QuantitiesState extends State<Quantities> {
int counter = 1;
final productprice;
final productimage;
_QuantitiesState(this.productprice, this.productimage);
void increment() {
setState(() {
counter++;
});
}
void decrement() {
setState(() {
counter--;
});
}
@override
Widget build(BuildContext context) {
return PlatformScaffold(
appBar: PlatformAppBar(
backgroundColor: Colors.lightBlue[900],
title: Text('Quantities'),
),
body: Padding(
padding: const EdgeInsets.only(top: 10.0),
child: ListView(
children: <Widget>[
new Container(
height: 200.0,
child: GridTile(
child: Container(
color: Colors.white,
child: Image.asset(productimage),),),),
Center(
child: Text(
productprice,),),
Padding(
padding: const EdgeInsets.only(top: 10.0),
child: Row(
mainAxisAlignment: MainAxisAlignment.center,
children: <Widget>[
Padding(
padding: const EdgeInsets.only(right: 10.0),
child: PlatformButton(
onPressed: () {
decrement();
if (counter < 1) {
counter = 1;
}
},
child: Text(
'-',
),
androidFlat: (_) =>
MaterialFlatButtonData(color: Colors.cyan),
ios: (_) => CupertinoButtonData(
color: Colors.cyan
)),
),
Text(
'$counter',
),
Padding(
padding: const EdgeInsets.only(left: 10.0),
child: PlatformButton(
onPressed: () {
increment();
},
child: Text(
'+',
style: TextStyle(color: Colors.white, fontSize: 30.0),
),
androidFlat: (_) =>
MaterialFlatButtonData(color: Colors.cyan),
ios: (_) => CupertinoButtonData(
color: Colors.cyan
)),
解决方案
这是完整的代码示例:
import 'package:flutter/material.dart';
import 'package:project_app/proyects/home.dart';
void main() => runApp(MyApp());
class MyApp extends StatelessWidget {
@override
Widget build(BuildContext context) {
return MaterialApp(
title: 'Product price',
theme: ThemeData(
primarySwatch: Colors.blue,
),
home: Quantities(productimage: "",productprice: "20$",),
);
}
}
class Quantities extends StatefulWidget {
final productprice;
final productimage;
Quantities({this.productprice, this.productimage});
@override
_QuantitiesState createState() =>
_QuantitiesState(productprice, productimage);
}
class _QuantitiesState extends State<Quantities> {
int counter = 1;
final productprice;
double finalprice;
final productimage;
final productp =productprice.replaceAll(new RegExp(r'\$'), '');
_QuantitiesState(this.productprice, this.productimage);
void increment() {
setState(() {
counter++;
finalprice=double.parse(productp)*counter;
});
}
void decrement() {
setState(() {
counter--;
finalprice=double.parse(productp)*counter;
});
}
@override
void initState() {
super.initState();
finalprice= double.parse(productp);
}
@override
Widget build(BuildContext context) {
return Scaffold(
appBar: AppBar(
backgroundColor: Colors.lightBlue[900],
title: Text('Quantities'),
),
body: Padding(
padding: const EdgeInsets.only(top: 10.0),
child: ListView(
children: <Widget>[
Center(
child: Text(
finalprice.toString(),
),
),
Padding(
padding: const EdgeInsets.only(top: 10.0),
child: Row(
mainAxisAlignment: MainAxisAlignment.center,
children: <Widget>[
Padding(
padding: const EdgeInsets.only(right: 10.0),
child: FlatButton(
onPressed: () {
if (counter > 1) {
decrement();
}
},
child: Text(
'-',
),
),
),
Text(
'$counter',
),
Padding(
padding: const EdgeInsets.only(left: 10.0),
child: FlatButton(
onPressed: () {
increment();
},
child: Text(
'+',
style:
TextStyle(color: Colors.white, fontSize: 30.0),
),
),
),
]),
),
],
),
));
}
}
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