如何在颤动中将按钮放在屏幕的两端
How to put buttons on two ends of screen in flutter
我希望 flutter 上的按钮位于屏幕的两侧，即一个在右下角，一个在左下角。
我想要屏幕左侧的减号按钮：
我在网上搜索过，但找不到任何帮助，我尝试使用对齐，但它只是给出了一些混乱。
我的 flutter 代码是（演示应用程序中的一些更改和使用对齐）：
void main() {
runApp(const MyApp());
}
class MyApp extends StatelessWidget {
const MyApp({Key? key}) : super(key: key);
// This widget is the root of your application.
@override
Widget build(BuildContext context) {
return MaterialApp(
title: 'Flutter Demo',
theme: ThemeData(
// This is the theme of your application.
//
// Try running your application with "flutter run". You'll see the
// application has a blue toolbar. Then, without quitting the app, try
// changing the primarySwatch below to Colors.green and then invoke
// "hot reload" (press "r" in the console where you ran "flutter run",
// or simply save your changes to "hot reload" in a Flutter IDE).
// Notice that the counter didn't reset back to zero; the application
// is not restarted.
primarySwatch: Colors.red,
),
home: const MyHomePage(title: 'Flutter Demo Home Page'),
);
}
}
class MyHomePage extends StatefulWidget {
const MyHomePage({Key? key, required this.title}) : super(key: key);
// This widget is the home page of your application. It is stateful, meaning
// that it has a State object (defined below) that contains fields that affect
// how it looks.
// This class is the configuration for the state. It holds the values (in this
// case the title) provided by the parent (in this case the App widget) and
// used by the build method of the State. Fields in a Widget subclass are
// always marked "final".
final String title;
@override
State<MyHomePage> createState() => _MyHomePageState();
}
class _MyHomePageState extends State<MyHomePage> {
int _counter = 0;
void _incrementCounter() {
setState(() {
// This call to setState tells the Flutter framework that something has
// changed in this State, which causes it to rerun the build method below
// so that the display can reflect the updated values. If we changed
// _counter without calling setState(), then the build method would not be
// called again, and so nothing would appear to happen.
_counter++;
});
}
void _decrementCounter(){
setState(() {
-_counter --;
});
}
@override
Widget build(BuildContext context) {
// This method is rerun every time setState is called, for instance as done
// by the _incrementCounter method above.
//
// The Flutter framework has been optimized to make rerunning build methods
// fast, so that you can just rebuild anything that needs updating rather
// than having to individually change instances of widgets.
return Scaffold(
appBar: AppBar(
// Here we take the value from the MyHomePage object that was created by
// the App.build method, and use it to set our appbar title.
title: Text(widget.title),
),
body: Center(
// Center is a layout widget. It takes a single child and positions it
// in the middle of the parent.
child: Column(
// Column is also a layout widget. It takes a list of children and
// arranges them vertically. By default, it sizes itself to fit its
// children horizontally, and tries to be as tall as its parent.
//
// Invoke "debug painting" (press "p" in the console, choose the
// "Toggle Debug Paint" action from the Flutter Inspector in Android
// Studio, or the "Toggle Debug Paint" command in Visual Studio Code)
// to see the wireframe for each widget.
//
// Column has various properties to control how it sizes itself and
// how it positions its children. Here we use mainAxisAlignment to
// center the children vertically; the main axis here is the vertical
// axis because Columns are vertical (the cross axis would be
// horizontal).
mainAxisAlignment: MainAxisAlignment.center,
children: <Widget>[
const Text(
'You have pushed the button this many times:',
),
Text(
'$_counter',
style: Theme.of(context).textTheme.headline4,
),
],
),
),
floatingActionButton:
Row(
mainAxisAlignment: MainAxisAlignment.end,
children :
[
Align(
alignment: Alignment.bottomLeft,
child : FloatingActionButton(
onPressed: _decrementCounter,
tooltip: 'decrement',
child: const Icon(Icons.remove),
heroTag: null,
)),
FloatingActionButton(
onPressed: _incrementCounter,
tooltip: 'Increment',
child: const Icon(Icons.add),
heroTag: null,
) ,
]),
// This trailing comma makes auto-formatting nicer for build methods.
);
}
}
我怎样才能做到这一点？
一种选择是在 Row 小部件中使用 mainAxisAlignment: MainAxisAlignment.spaceBetween，并结合设置 floatingActionButtonLocation: FloatingActionButtonLocation.centerFloat。可以用Padding横向加一些space：
floatingActionButtonLocation: FloatingActionButtonLocation.centerFloat,
floatingActionButton: Padding(
padding: const EdgeInsets.symmetric(horizontal: 16.0),
child:
Row(mainAxisAlignment: MainAxisAlignment.spaceBetween, children: [
FloatingActionButton(
onPressed: _decrementCounter,
tooltip: 'decrement',
child: const Icon(Icons.remove),
heroTag: null,
),
FloatingActionButton(
onPressed: _incrementCounter,
tooltip: 'Increment',
child: const Icon(Icons.add),
heroTag: null,
),
])),
但是你最初的计划 Align 也可以，你只需要将两个 FAB 放入一个 Stack 小部件中，这意味着它们将相互放置（如图层） , 可以分别设置左下对齐和右下对齐:
floatingActionButtonLocation: FloatingActionButtonLocation.centerFloat,
floatingActionButton: Padding(
padding: const EdgeInsets.symmetric(horizontal: 16.0),
child: Stack(children: [
Align(
alignment: Alignment.bottomLeft,
child: FloatingActionButton(
onPressed: _decrementCounter,
tooltip: 'decrement',
child: const Icon(Icons.remove),
heroTag: null,
)),
Align(
alignment: Alignment.bottomRight,
child: FloatingActionButton(
onPressed: _incrementCounter,
tooltip: 'Increment',
child: const Icon(Icons.add),
heroTag: null,
)),
])),
我希望 flutter 上的按钮位于屏幕的两侧，即一个在右下角，一个在左下角。
我想要屏幕左侧的减号按钮：
我在网上搜索过，但找不到任何帮助，我尝试使用对齐，但它只是给出了一些混乱。
我的 flutter 代码是（演示应用程序中的一些更改和使用对齐）：
void main() {
runApp(const MyApp());
}
class MyApp extends StatelessWidget {
const MyApp({Key? key}) : super(key: key);
// This widget is the root of your application.
@override
Widget build(BuildContext context) {
return MaterialApp(
title: 'Flutter Demo',
theme: ThemeData(
// This is the theme of your application.
//
// Try running your application with "flutter run". You'll see the
// application has a blue toolbar. Then, without quitting the app, try
// changing the primarySwatch below to Colors.green and then invoke
// "hot reload" (press "r" in the console where you ran "flutter run",
// or simply save your changes to "hot reload" in a Flutter IDE).
// Notice that the counter didn't reset back to zero; the application
// is not restarted.
primarySwatch: Colors.red,
),
home: const MyHomePage(title: 'Flutter Demo Home Page'),
);
}
}
class MyHomePage extends StatefulWidget {
const MyHomePage({Key? key, required this.title}) : super(key: key);
// This widget is the home page of your application. It is stateful, meaning
// that it has a State object (defined below) that contains fields that affect
// how it looks.
// This class is the configuration for the state. It holds the values (in this
// case the title) provided by the parent (in this case the App widget) and
// used by the build method of the State. Fields in a Widget subclass are
// always marked "final".
final String title;
@override
State<MyHomePage> createState() => _MyHomePageState();
}
class _MyHomePageState extends State<MyHomePage> {
int _counter = 0;
void _incrementCounter() {
setState(() {
// This call to setState tells the Flutter framework that something has
// changed in this State, which causes it to rerun the build method below
// so that the display can reflect the updated values. If we changed
// _counter without calling setState(), then the build method would not be
// called again, and so nothing would appear to happen.
_counter++;
});
}
void _decrementCounter(){
setState(() {
-_counter --;
});
}
@override
Widget build(BuildContext context) {
// This method is rerun every time setState is called, for instance as done
// by the _incrementCounter method above.
//
// The Flutter framework has been optimized to make rerunning build methods
// fast, so that you can just rebuild anything that needs updating rather
// than having to individually change instances of widgets.
return Scaffold(
appBar: AppBar(
// Here we take the value from the MyHomePage object that was created by
// the App.build method, and use it to set our appbar title.
title: Text(widget.title),
),
body: Center(
// Center is a layout widget. It takes a single child and positions it
// in the middle of the parent.
child: Column(
// Column is also a layout widget. It takes a list of children and
// arranges them vertically. By default, it sizes itself to fit its
// children horizontally, and tries to be as tall as its parent.
//
// Invoke "debug painting" (press "p" in the console, choose the
// "Toggle Debug Paint" action from the Flutter Inspector in Android
// Studio, or the "Toggle Debug Paint" command in Visual Studio Code)
// to see the wireframe for each widget.
//
// Column has various properties to control how it sizes itself and
// how it positions its children. Here we use mainAxisAlignment to
// center the children vertically; the main axis here is the vertical
// axis because Columns are vertical (the cross axis would be
// horizontal).
mainAxisAlignment: MainAxisAlignment.center,
children: <Widget>[
const Text(
'You have pushed the button this many times:',
),
Text(
'$_counter',
style: Theme.of(context).textTheme.headline4,
),
],
),
),
floatingActionButton:
Row(
mainAxisAlignment: MainAxisAlignment.end,
children :
[
Align(
alignment: Alignment.bottomLeft,
child : FloatingActionButton(
onPressed: _decrementCounter,
tooltip: 'decrement',
child: const Icon(Icons.remove),
heroTag: null,
)),
FloatingActionButton(
onPressed: _incrementCounter,
tooltip: 'Increment',
child: const Icon(Icons.add),
heroTag: null,
) ,
]),
// This trailing comma makes auto-formatting nicer for build methods.
);
}
}
我怎样才能做到这一点？
一种选择是在 Row 小部件中使用 mainAxisAlignment: MainAxisAlignment.spaceBetween，并结合设置 floatingActionButtonLocation: FloatingActionButtonLocation.centerFloat。可以用Padding横向加一些space：
floatingActionButtonLocation: FloatingActionButtonLocation.centerFloat,
floatingActionButton: Padding(
padding: const EdgeInsets.symmetric(horizontal: 16.0),
child:
Row(mainAxisAlignment: MainAxisAlignment.spaceBetween, children: [
FloatingActionButton(
onPressed: _decrementCounter,
tooltip: 'decrement',
child: const Icon(Icons.remove),
heroTag: null,
),
FloatingActionButton(
onPressed: _incrementCounter,
tooltip: 'Increment',
child: const Icon(Icons.add),
heroTag: null,
),
])),
但是你最初的计划 Align 也可以，你只需要将两个 FAB 放入一个 Stack 小部件中，这意味着它们将相互放置（如图层） , 可以分别设置左下对齐和右下对齐:
floatingActionButtonLocation: FloatingActionButtonLocation.centerFloat,
floatingActionButton: Padding(
padding: const EdgeInsets.symmetric(horizontal: 16.0),
child: Stack(children: [
Align(
alignment: Alignment.bottomLeft,
child: FloatingActionButton(
onPressed: _decrementCounter,
tooltip: 'decrement',
child: const Icon(Icons.remove),
heroTag: null,
)),
Align(
alignment: Alignment.bottomRight,
child: FloatingActionButton(
onPressed: _incrementCounter,
tooltip: 'Increment',
child: const Icon(Icons.add),
heroTag: null,
)),
])),