forked from lxm_flutter/FlutterUnit
118 lines
3.8 KiB
Dart
118 lines
3.8 KiB
Dart
import 'package:flutter/material.dart';
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/// create by 张风捷特烈 on 2020/9/21
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/// contact me by email 1981462002@qq.com
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/// 说明: 349 ScrollView 滑动视图
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/// 该组件用于滑动的支持，该类是一个抽象类，所以无法直接使用，它有很多实现类，如 CustomScrollView、BoxScrollView、ListView、GridView。
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/// link 183,162,163,253,340
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///
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// {
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// "widgetId": 349,
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// "name": 'ScrollView 介绍',
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// "priority": 1,
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// "subtitle": "【reverse】 : 是否反向 【bool】\n"
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// "【scrollDirection】 : 滑动方向 【Axis】\n"
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// "【cacheExtent】 : 缓存长 【double】\n"
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// "【dragStartBehavior】 : 拖动行为 【DragStartBehavior】\n"
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// "【clipBehavior】 : 裁剪行为 【ClipBehavior】\n"
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// "【controller】 : 控制器 【ScrollController】",
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// }
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class ScrollViewDemo extends StatelessWidget {
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const ScrollViewDemo({Key? key}) : super(key: key);
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@override
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Widget build(BuildContext context) {
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return SizedBox(
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height: 300,
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child: MyScrollView(),
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);
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}
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}
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class MyScrollView extends ScrollView {
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MyScrollView({Key? key}) : super(key: key);
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final String info =
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'ScrollView 其内部依靠 Viewport + Scrollable 实现滑动。它只有一个 buildSlivers 的抽象方法，返回 Sliver 家族 Widget 列表，'
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'其子类最简单的是 CustomScrollView，将 slivers 交由用户传递，自身打个酱油。'
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'ListView 和 GridView 在底层源码中也是使用 Sliver 家族相关组件实现的。';
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final List<Color> data = [
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Colors.purple[50]!,
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Colors.purple[100]!,
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Colors.purple[200]!,
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Colors.purple[300]!,
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Colors.purple[400]!,
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Colors.purple[500]!,
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Colors.purple[600]!,
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Colors.purple[700]!,
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Colors.purple[800]!,
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Colors.purple[900]!,
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];
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@override
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List<Widget> buildSlivers(BuildContext context) {
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return [
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_buildSliverAppBar(),
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SliverToBoxAdapter(
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child: Container(
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color: Colors.blue.withOpacity(0.1),
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padding: const EdgeInsets.all(10),
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margin: const EdgeInsets.all(10),
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child: Text(info),
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),
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),
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_buildSliverFixedExtentList()
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];
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}
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_buildSliverAppBar() {
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return SliverAppBar(
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expandedHeight: 190.0,
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leading: Container(
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margin: const EdgeInsets.all(10),
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child: Image.asset('assets/images/icon_head.webp')),
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flexibleSpace: FlexibleSpaceBar(//伸展处布局
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titlePadding: const EdgeInsets.only(left: 55, bottom: 15), //标题边距
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collapseMode: CollapseMode.parallax, //视差效果
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title: const Text(
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'张风捷特烈',
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style: TextStyle(color: Colors.black, //标题
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shadows: [
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Shadow(color: Colors.blue, offset: Offset(1, 1), blurRadius: 2)
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]),
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),
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background: Image.asset(
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"assets/images/caver.webp",
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fit: BoxFit.cover,
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),
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),
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);
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}
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Widget _buildSliverFixedExtentList() => SliverFixedExtentList(
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itemExtent: 60,
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delegate: SliverChildBuilderDelegate(
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(_, int index) => Container(
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alignment: Alignment.center,
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width: 100,
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height: 50,
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color: data[index],
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child: Text(
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colorString(data[index]),
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style: const TextStyle(color: Colors.white, shadows: [
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Shadow(
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color: Colors.black,
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offset: Offset(.5, .5),
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blurRadius: 2)
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]),
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),
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),
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childCount: data.length),
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);
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String colorString(Color color) =>
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"#${color.value.toRadixString(16).padLeft(8, '0').toUpperCase()}";
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}
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