[英]Change Background Color of Elevated Button OnPressed in Flutter
[英]Flutter - image change with onPressed (not in a button)
我是 StackOverflow 和 flutter 游戲的新手,並嘗試為 web 編寫應用程序。 也許這是一個簡單的問題,但我不知道該怎么做。 我有問題,我不知道如何更改已顯示的圖像。
我的目標是 3 個按鈕,可以更改它們上方的圖像。 可以顯示其中一張圖像或在開始時用占位符替換,這並不重要。
可能代碼中有一些不必要的function,忽略它們。
如果你能幫助我,那就太好了。
import 'package:flutter/material.dart';
void main() {
runApp(StarCounter());
}
class StarCounter extends StatelessWidget {
// This widget is the root of your application.
@override
Widget build(BuildContext context) {
return MaterialApp(
title: 'Screen',
theme: ThemeData(
primarySwatch: Colors.orange,
visualDensity: VisualDensity.adaptivePlatformDensity,
),
home: MyHomePage(title: 'Screen'),
);
}
}
class MyHomePage extends StatefulWidget {
MyHomePage({Key key, this.title}) : super(key: key);
final String title;
@override
_MyHomePageState createState() => _MyHomePageState();
}
class _MyHomePageState extends State<MyHomePage> {
var _itemImage = Image.asset("Screenshot1.png");
tmpFunction() {
Container(
child: _itemImage,
width: 500,
);
}
@override
Widget build(BuildContext context) {
return Scaffold(
appBar: AppBar(
title: Text(widget.title),
),
body: Center(
child: Column(
mainAxisAlignment: MainAxisAlignment.center,
children: <Widget>[
Container(
child: Placeholder(
fallbackWidth: 500,
),
),
Text(
'Wählen Sie den gewünschten Button aus:',
),
Row(
mainAxisAlignment: MainAxisAlignment.center,
children: [
FlatButton(onPressed: tmpFunction, child: Text("Button 1")),
FlatButton(onPressed: tmpFunction, child: Text("Button 2")),
FlatButton(onPressed: tmpFunction, child: Text("Button 3")),
],
),
],
),
),
);
}
}
每個按鈕都會改變圖像你可以改變用戶資產圖像或網絡圖像
import 'package:flutter/material.dart';
void main() {
runApp(StarCounter());
}
class StarCounter extends StatelessWidget {
// This widget is the root of your application.
@override
Widget build(BuildContext context) {
return MaterialApp(
title: 'Screen',
theme: ThemeData(
primarySwatch: Colors.orange,
visualDensity: VisualDensity.adaptivePlatformDensity,
),
home: MyHomePage(title: 'Screen'),
);
}
}
class MyHomePage extends StatefulWidget {
MyHomePage({Key key, this.title}) : super(key: key);
final String title;
@override
_MyHomePageState createState() => _MyHomePageState();
}
class _MyHomePageState extends State<MyHomePage> {
var _itemImage = [
Image.network("https://i.picsum.photos/id/203/200/300.jpg?
hmac=mJaqsySlyEjr8fLBHytyVCUyqlfPSxqXePXEIhZZi_Y"),
Image.network("https://i.picsum.photos/id/14/200/200.jpg?hmac=bwQwH7-
0RPCqUVkFzd3hFhc6yDfC6_e7vgaKXZ7vFOA"),
Image.network("https://picsum.photos/id/870/200/300?grayscale&blur=2")];
int index =0;
tmpFunction() {
Container(
child: _itemImage[index],
width: 500,
);
}
@override
Widget build(BuildContext context) {
return Scaffold(
appBar: AppBar(
title: Text(widget.title),
),
body: Center(
child: Column(
mainAxisAlignment: MainAxisAlignment.center,
children: <Widget>[
Container(
child: _itemImage[index],
width: 500,
),
Text(
'Wählen Sie den gewünschten Button aus:',
),
Row(
mainAxisAlignment: MainAxisAlignment.center,
children: [
FlatButton(onPressed: (){
setState(() { index = 0;});
}, child: Text("Button 1")),
FlatButton(onPressed: (){
setState(() { index = 1;});
}, child: Text("Button 2")),
FlatButton(onPressed: (){
setState(() { index = 2;});
}, child: Text("Button 3")),
],
),
],
),
),
);
}
}
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