Flutter pageview切换指示器的实现代码
PageView 是一个滑动视图列表,它也是继承至 CustomScrollView 的。
在 PageView 里有三个构造函数:
- PageView - 创建一个可滚动列表。
- PageView.builder - 创建一个滚动列表,指定数量。
- PageView.custom - 创建一个可滚动的列表,自定义子项。
效果
代码
// Copyright 2017, the Flutter project authors. Please see the AUTHORS file // for details. All rights reserved. Use of this source code is governed by a // BSD-style license that can be found in the LICENSE file. import 'dart:math'; import 'package:flutter/material.dart'; void main() { runApp(new MyApp()); } class MyApp extends StatelessWidget { @override Widget build(BuildContext context) { return new MaterialApp( title: 'Flutter Demo', home: new MyHomePage(), debugShowCheckedModeBanner: false, ); } } /// An indicator showing the currently selected page of a PageController class DotsIndicator extends AnimatedWidget { DotsIndicator({ this.controller, this.itemCount, this.onPageSelected, this.color: Colors.white, }) : super(listenable: controller); /// The PageController that this DotsIndicator is representing. final PageController controller; /// The number of items managed by the PageController final int itemCount; /// Called when a dot is tapped final ValueChanged<int> onPageSelected; /// The color of the dots. /// /// Defaults to `Colors.white`. final Color color; // The base size of the dots static const double _kDotSize = 8.0; // The increase in the size of the selected dot static const double _kMaxZoom = 2.0; // The distance between the center of each dot static const double _kDotSpacing = 25.0; Widget _buildDot(int index) { double selectedness = Curves.easeOut.transform( max( 0.0, 1.0 - ((controller.page ?? controller.initialPage) - index).abs(), ), ); double zoom = 1.0 + (_kMaxZoom - 1.0) * selectedness; return new Container( width: _kDotSpacing, child: new Center( child: new Material( color: color, type: MaterialType.circle, child: new Container( width: _kDotSize * zoom, height: _kDotSize * zoom, child: new InkWell( onTap: () => onPageSelected(index), ), ), ), ), ); } Widget build(BuildContext context) { return new Row( mainAxisAlignment: MainAxisAlignment.center, children: new List<Widget>.generate(itemCount, _buildDot), ); } } class MyHomePage extends StatefulWidget { @override State createState() => new MyHomePageState(); } class MyHomePageState extends State<MyHomePage> { final _controller = new PageController(); static const _kDuration = const Duration(milliseconds: 300); static const _kCurve = Curves.ease; final _kArrowColor = Colors.black.withOpacity(0.8); final List<Widget> _pages = <Widget>[ new ConstrainedBox( constraints: const BoxConstraints.expand(), child: new FlutterLogo(colors: Colors.blue), ), new ConstrainedBox( constraints: const BoxConstraints.expand(), child: new FlutterLogo(style: FlutterLogoStyle.stacked, colors: Colors.red), ), new ConstrainedBox( constraints: const BoxConstraints.expand(), child: new FlutterLogo(style: FlutterLogoStyle.horizontal, colors: Colors.green), ), ]; @override Widget build(BuildContext context) { return new Scaffold( body: new IconTheme( data: new IconThemeData(color: _kArrowColor), child: new Stack( children: <Widget>[ new PageView.builder( physics: new AlwaysScrollableScrollPhysics(), controller: _controller, itemBuilder: (BuildContext context, int index) { return _pages[index % _pages.length]; }, ), new Positioned( bottom: 0.0, left: 0.0, right: 0.0, child: new Container( color: Colors.grey[800].withOpacity(0.5), padding: const EdgeInsets.all(20.0), child: new Center( child: new DotsIndicator( controller: _controller, itemCount: _pages.length, onPageSelected: (int page) { _controller.animateToPage( page, duration: _kDuration, curve: _kCurve, ); }, ), ), ), ), ], ), ), ); } }
PageView 有以下常用属性:
- childrenDelegate → SliverChildDelegate - 子项列表。
- controller → PageController - 控制台。
- onPageChanged → ValueChanged - 索引改变时触发。
- pageSnapping → bool - 设置为 false 以禁用页面捕捉,对自定义滚动行为很有用。
- physics → ScrollPhysics - 页面视图如何响应用户输入,即滚动的动画表现。
- reverse → bool - 是否反方向。
- scrollDirection → Axis - 视图滚动的方向。
以上就是本文的全部内容,希望对大家的学习有所帮助,也希望大家多多支持我们。
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