Flutter GestureDetector,onTap自动触发,怎么办? [英] Flutter GestureDetector, onTap gets triggered automatically, how to?
问题描述
我有一个有状态的小部件,其中有一个简单的网格,每个网格单元中都有一个容器.
I have a stateful widget that has a simple grid and each grid cell has a container inside it.
我想单击一个单元格/容器并更改其内容.
I would like to click on a cell / container and have its content changed.
问题在于,对于所有cel,应用刷新时都会触发GestureDetector-> onTap方法.
The problem is that the GestureDetector -> onTap method gets triggered on app refresh for all cels.
在下面的示例中,_changeCell
方法立即针对所有cel触发,并且onTap
不起作用.
In the example below, the _changeCell
method gets triggered instantly for all cels and onTap
doesn't work.
有什么想法吗?
import 'package:flutter/material.dart';
class GridWidget extends StatefulWidget {
@override
_GridWidgetState createState() => new _GridWidgetState();
}
class _GridWidgetState extends State<GridWidget> {
@override
Widget build(BuildContext context) {
Color cellColor = Colors.white;
Text cellText = new Text('');
// when a cell is tapped, change the color and text
_changeCell(index) {
setState(() {
cellColor = Colors.lightBlue;
cellText = new Text('clicked');
});
print("Container clicked " + index.toString());
}
// create a 5 by 5 grid
return new GridView.count(
crossAxisCount: 5,
children: new List.generate(5, (index) {
return new GestureDetector(
onTap: _changeCell(index),
child: new Container(
width: double.infinity,
height: double.infinity,
decoration: new BoxDecoration(
color: cellColor,
),
child: new Center(
child: cellText,
),
),
);
}),
);
}
}
推荐答案
只需将onTap: _changeCell(index)
更改为onTap: () => _changeCell(index)
即可. _changeCell(index)会返回 null ,您将null设置为onTap并调用相同的函数.
just change onTap: _changeCell(index)
to onTap: () => _changeCell(index)
. _changeCell(index) this returns null and you setting null to onTap and calling the same function .
以下代码是为此
我玩了一些.
import 'package:flutter/material.dart';
void main() {
runApp(new MaterialApp(
home: new DemoScreen(),
));
}
class DemoScreen extends StatefulWidget {
@override
_DemoScreenState createState() => new _DemoScreenState();
}
class _DemoScreenState extends State<DemoScreen> {
Color cellColor = Colors.white;
Text _getText(index) {
Text text;
switch (index) {
case 0:
text = new Text('lightBlue');
break;
case 1:
text = new Text('red');
break;
case 2:
text = new Text('green');
break;
case 3:
text = new Text('yellow');
break;
case 4:
text = new Text('orange');
break;
default:
text = new Text('brown');
break;
}
return text;
}
@override
Widget build(BuildContext context) {
return new Scaffold(
appBar: new AppBar(
title: new Text("Demo App"),
),
body: new GridView.count(
crossAxisCount: 5,
children: new List.generate(5, (index) {
return new MyWidget(
index: index,
color: cellColor,
text: _getText(index),
);
}),
),
);
}
}
class MyWidget extends StatefulWidget {
final Color color;
final Text text;
final int index;
MyWidget({this.color, this.text, this.index});
@override
_MyWidgetState createState() => new _MyWidgetState();
}
class _MyWidgetState extends State<MyWidget> {
Color cellColor = Colors.white;
Text cellText = new Text('white');
@override
void initState() {
super.initState();
cellColor = widget.color;
cellText = widget.text;
}
_changeCell(index) {
setState(() {
switch (index) {
case 0:
cellColor = Colors.lightBlue;
cellText = new Text('lightBlue');
break;
case 1:
cellColor = Colors.red;
cellText = new Text('red');
break;
case 2:
cellColor = Colors.green;
cellText = new Text('green');
break;
case 3:
cellColor = Colors.yellow;
cellText = new Text('yellow');
break;
case 4:
cellColor = Colors.orange;
cellText = new Text('orange');
break;
default:
cellColor = Colors.brown;
cellText = new Text('brown');
break;
}
});
print("Container clicked " + index.toString());
}
@override
Widget build(BuildContext context) {
return new GestureDetector(
onTap: () => _changeCell(widget.index),
child: new Container(
margin: new EdgeInsets.symmetric(horizontal: 1.0),
width: double.infinity,
height: double.infinity,
decoration: new BoxDecoration(
color: cellColor,
),
child: new Center(
child: cellText,
),
),
);
}
}
希望它会有所帮助:)
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