基本上我有一个带有元素的滑动屏幕，用户可以在其中向左或向右滑动。当用户滑动时，我调用了一些函数。我GestureDetector用于手势识别和PageView.Custom我的物品。可能ListView.Custom也有效，但它不能解决我的问题。
我需要一个PageController，因为我必须以编程方式控制导航。而且我认为这PageController可能是我的函数被多次调用的问题背后的原因。如何解决？有人知道为什么setstate经常被调用以及如何防止它吗？
我为您提供了一个完整的工作示例（缩小版），其中包含向右滑动操作的打印，您可以在其中看到它的beeing 被多次调用。
import 'package:flutter/gestures.dart';
import 'package:flutter/material.dart';
void main() {
runApp(MyApp());
}
class MyApp extends StatelessWidget {
// This widget is the root of your application.
@override
Widget build(BuildContext context) {
return MaterialApp(
title: 'Flutter Demo',
theme: ThemeData(
primarySwatch: Colors.blue,
),
home: MyHomePage(),
);
}
}
class MyHomePage extends StatefulWidget {
@override
_MyHomePageState createState() => _MyHomePageState();
}
class _MyHomePageState extends State<MyHomePage> {
int currentIndex = 0;
@override
Widget build(BuildContext context) {
// Page selector for tab list
void _selectPage(int index) {
print('page index: $index');
setState(() {
currentIndex = index;
});
}
// Routes list for tab navigation Android
final List<Widget> _pages = [
ScreenA(),
ScreenB(func: _selectPage),
];
return Scaffold(
appBar: AppBar(),
body: _pages[currentIndex],
bottomNavigationBar: SafeArea(
child: BottomNavigationBar(
onTap: _selectPage,
iconSize: 22,
currentIndex: currentIndex,
type: BottomNavigationBarType.fixed,
items: [
BottomNavigationBarItem(
backgroundColor: Theme.of(context).primaryColor,
icon: Icon(Icons.description),
label: 'ScreenA',
),
BottomNavigationBarItem(
backgroundColor: Theme.of(context).primaryColor,
icon: Icon(Icons.ac_unit_outlined),
label: 'ScreenB'),
],
),
),
);
}
}
class ScreenA extends StatelessWidget {
@override
Widget build(BuildContext context) {
return Container(
child: Text('HOME'),
);
}
}
class ScreenB extends StatefulWidget {
Function func;
ScreenB({Key key, @required this.func})
: super(key: key);
@override
_ScreenBState createState() => _ScreenBState();
}
class _ScreenBState extends State<ScreenB> {
_ScreenBState();
var _controller = PageController();
@override
Widget build(BuildContext context) {
return Scaffold(
appBar: AppBar(
actions: [
IconButton(
icon: Icon(Icons.access_alarm_sharp),
onPressed: () async {
widget.func(0);
},
),
],
),
body: PageView.custom(
dragStartBehavior: DragStartBehavior.start,
controller: _controller,
physics: NeverScrollableScrollPhysics(),
scrollDirection: Axis.horizontal,
childrenDelegate: SliverChildBuilderDelegate((ctx, pageIndex) =>
GestureDetector(
onPanUpdate: (details) async {
if (details.delta.dx < 0) {
_controller.nextPage(
duration: Duration(milliseconds: 200),
curve: Curves.easeInOut);
print('function called');
}
},
child: Center(
child: Container(
width: 200,
height: 200,
color: Colors.red,
child: Text('hi')))))),
);
}
}
提前致谢！