forked from lxm_flutter/FlutterUnit
126 lines
3.3 KiB
Dart
126 lines
3.3 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: 239 AutomaticKeepAlive 自动保活 在懒加载的列表中，允许子树请求保持状态，单独使用无效果，需要配合 KeepAliveNotification 使用。
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/// link 59,162,163,165,185,188
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///
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// {
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// "widgetId": 239,
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// "name": 'AutomaticKeepAlive 介绍',
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// "priority": 1,
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// "subtitle":
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// "【child】 : 子组件 【Widget】\n"
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// "在 ListView、SliverList、GridView、SliverGrid、PageView、TabBarView 等列表、切页组件源码中都有使用到 AutomaticKeepAlive 组件。在保活某个 State 时，可以使用 AutomaticKeepAliveClientMixin 进行操作，它是对 KeepAliveNotification 使用的一个简易封装。该示例展示出 ListView 条目的状态保活。",
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// }
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class AutomaticKeepAliveDemo extends StatelessWidget {
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AutomaticKeepAliveDemo({Key? key}) : super(key: key);
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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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Colors.red[50]!,
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Colors.red[100]!,
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Colors.red[200]!,
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Colors.red[300]!,
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Colors.red[400]!,
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Colors.red[500]!,
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Colors.red[600]!,
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Colors.red[700]!,
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Colors.red[800]!,
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Colors.red[900]!,
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];
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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: ListView.builder(
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itemCount: data.length,
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itemBuilder: (_, index) => ColorBox(
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color: data[index],
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index: index,
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),
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),
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);
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}
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}
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class ColorBox extends StatefulWidget {
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final Color color;
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final int index;
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const ColorBox({Key? key, required this.color, required this.index})
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: super(key: key);
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@override
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_ColorBoxState createState() => _ColorBoxState();
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}
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class _ColorBoxState extends State<ColorBox> with AutomaticKeepAliveClientMixin {
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bool _checked = false;
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@override
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void initState() {
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super.initState();
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_checked = false;
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print('-----_ColorBoxState#initState---${widget.index}-------');
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}
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@override
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void dispose() {
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print('-----_ColorBoxState#dispose---${widget.index}-------');
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super.dispose();
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}
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@override
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Widget build(BuildContext context) {
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super.build(context);
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return Container(
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alignment: Alignment.center,
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height: 50,
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color: widget.color,
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child: Row(
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children: [
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const SizedBox(
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width: 60,
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),
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Checkbox(
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value: _checked,
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onChanged: (bool? v) {
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setState(() {
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_checked = v ?? false;
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});
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},
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),
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Text(
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"index ${widget.index}: ${colorString(widget.color)}",
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style: const TextStyle(color: Colors.white, shadows: [
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Shadow(
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color: Colors.black,
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offset: Offset(.5, .5),
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blurRadius: 2,
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)
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]),
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),
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],
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),
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);
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}
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String colorString(Color color) =>
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"#${color.value.toRadixString(16).padLeft(8, '0').toUpperCase()}";
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@override
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bool get wantKeepAlive => true;
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}
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