当我单击“ +添加行”按钮时，我想添加6个球行（请参考image），但是我遇到了1个问题，即我不确定它是否具有像我编码的Listview。请帮助我完成“ void addRow（）”，以单击按钮添加一行。
并且您能给我一些提示，以获取如何获得与其他行完全不同的随机数的新行吗？
import 'dart:async';
import 'package:flutter/material.dart';
import 'package:flutter/services.dart';
import 'package:material_design_icons_flutter/material_design_icons_flutter.dart';
import 'dart:math';
import 'package:barcode_scan/barcode_scan.dart';
void main() => runApp(
MaterialApp(
home: BallPage()
),
);
class BallPage extends StatefulWidget {
@override
_BallPageState createState() => _BallPageState();
}
class _BallPageState extends State<BallPage>{
@override
Widget build(BuildContext context) {
return Scaffold(
backgroundColor: Colors.white,
drawer: new Drawer(),
appBar: AppBar(
title: Text(
'Magic 6 balls'),
backgroundColor: Colors.black,
actions: <Widget>[
new IconButton(
icon: new Icon(MdiIcons.squareInc),
color: Colors.white,
onPressed: () {
Navigator.push(context,
MaterialPageRoute(builder: (context) => SecondRoute())
);
},
),
],
),
body: Number(),
);
}
}
class SecondRoute extends StatefulWidget {
@override
_SecondRouteState createState() {
return new _SecondRouteState();
}
}
class _SecondRouteState extends State<SecondRoute>{
String result ="Hey there!";
Future _scanQR() async {
try{
String qrResult = await BarcodeScanner.scan();
setState(() {
result = qrResult;
});
} on PlatformException catch (ex) {
if (ex.code == BarcodeScanner.CameraAccessDenied){
setState(() {
result = "Camera permission was denied";
});
} else {
setState(() {
result = "Unknown Error $ex";
});
}
} on FormatException {
setState(() {
result = "You pressed the black button before scanning anything";
});
}catch (ex) {
setState(() {
result = "Unknown Error $ex";
});
}
}
@override
Widget build(BuildContext context) {
return Scaffold(
appBar: AppBar(
title: Text('QR Code Scan'),
),
body: Center(
child: Text(
result,
style: new TextStyle(fontSize: 20.0),
),
),
floatingActionButton: FloatingActionButton.extended(
onPressed: _scanQR,
label: Text('Scan'),
icon: Icon(Icons.camera_alt),
),
floatingActionButtonLocation: FloatingActionButtonLocation.centerFloat,
);
}
}
class Number extends StatefulWidget {
@override
_NumberState createState() => _NumberState();
}
class _NumberState extends State<Number> {
int ball1 = 1;
int ball2 = 1;
int ball3 = 1;
int ball4 = 1;
int ball5 = 1;
int ball6 = 1;
void randomNumbers() {
setState(() {
ball1 = Random().nextInt(49) + 1;
ball2 = Random().nextInt(49) + 1;
ball3 = Random().nextInt(49) + 1;
ball4 = Random().nextInt(49) + 1;
ball5 = Random().nextInt(49) + 1;
ball6 = Random().nextInt(49) + 1;
});
}
void addRows(){
setState(() {
});
}
void removeRows(){
setState(() {
});
}
@override
Widget build(BuildContext context) {
return Scaffold(
body: Center(
child: Row(
mainAxisAlignment: MainAxisAlignment.center,
children: <Widget>[
Expanded(
child: ListView(
children: <Widget>[
SizedBox(height: 100.0),
Center(
child: Text('Winners Number')
),
SizedBox(height: 16.0),
buildForm(),
SizedBox(height: 16.0),
RaisedButton.icon(
icon: Icon(Icons.add),
label: Text('Add Rows'),
onPressed: () {
addRows();
},
),
],
),
),
],
),
),
floatingActionButton: FloatingActionButton.extended(
onPressed: () {
randomNumbers();
},
label: Text(
'Click Here!'),
icon: Icon(
Icons.loop),
backgroundColor: Colors.black,
),
);
}
Widget buildForm() {
List<Widget> list = new List();
for (var index = 0; index < 1; index++) {
list.add(Row(
mainAxisAlignment: MainAxisAlignment.center,
children: <Widget>[
Container(
height: 60,
width: 60,
child: Center
(
child: Text(
'$ball1',
style: TextStyle(
fontSize: 20.0,
),
),
),
decoration: BoxDecoration(
color: Colors.yellow,
shape: BoxShape.circle,
),
),
Container(
height: 60,
width: 60,
child: Center
(
child: Text(
'$ball2',
style: TextStyle(
fontSize: 20.0,
),
),
),
decoration: BoxDecoration(
color: Colors.yellow,
shape: BoxShape.circle,
),
),
Container(
height: 60,
width: 60,
child: Center
(
child: Text(
'$ball3',
style: TextStyle(
fontSize: 20.0,
),
),
),
decoration: BoxDecoration(
color: Colors.yellow,
shape: BoxShape.circle,
),
),
Container(
height: 60,
width: 60,
child: Center
(
child: Text(
'$ball4',
style: TextStyle(
fontSize: 20.0,
),
),
),
decoration: BoxDecoration(
color: Colors.yellow,
shape: BoxShape.circle,
),
),
Container(
height: 60,
width: 60,
child: Center
(
child: Text(
'$ball5',
style: TextStyle(
fontSize: 20.0,
),
),
),
decoration: BoxDecoration(
color: Colors.yellow,
shape: BoxShape.circle,
),
),
Container(
height: 60,
width: 60,
child: Center
(
child: Text(
'$ball6',
style: TextStyle(
fontSize: 20.0,
color: Colors.white,
),
),
),
decoration: BoxDecoration(
color: Colors.black,
shape: BoxShape.circle,
),
),
],
));
list.add(
SizedBox(
height: 12.0,
));
}
return Column(
children: list);
}
}
我建议做的是，将行始终保留在其中，而仅使用可见性小部件将其隐藏。
添加一个整数计数器变量，并在每次单击addRow时将其递增。
然后将可见的球小部件包裹起来，并执行类似的操作：
伪代码
Visibilty(
visible: counter == 1,
child: BallWidget(),
)
...对于所有其他球形小部件，依此类推。
希望有帮助。
这只是生成与其他行完全不同的随机数的技巧。
此
ball1 = Random().nextInt(49) + 1;
ball2 = Random().nextInt(49) + 1;
ball3 = Random().nextInt(49) + 1;
ball4 = Random().nextInt(49) + 1;
ball5 = Random().nextInt(49) + 1;
ball6 = Random().nextInt(49) + 1;
有0.02040816326％的机会与前一行生成相同的随机数。
第一方式
您可以使用Random().nextInt(49) + 1。用Set randomSet = new Set();添加每个随机数randomSet.add(randomNumber)并使用if(randomNumber in randomSet)如果为true，则生成另一个。
第二种方式
如果您有6个球，也许您可以事先自己制作1-6个数字。首先创建列表，添加所有单个随机数，然后将其随机播放。这样，不会重复随机数。import 'dart:math'; List shuffle(List items) { var random = new Random(); // Go through all elements. for (var i = items.length - 1; i > 0; i--) { // Pick a pseudorandom number according to the list length var n = random.nextInt(i + 1); var temp = items[i]; items[i] = items[n]; items[n] = temp; } return items; } main() { var items = [1, 2, 3, 4, 5, 6]; print(shuffle(items)); }从此处的答案中获取的代码：List.shuffle() in Dart?
然后
ball1 = items[0]; ball2 = items[1]; ball3 = items[2]; ball4 = items[3]; ball5 = items[4]; ball6 = items[5];希望有帮助。