forked from lxm_flutter/FlutterUnit
119 lines
2.9 KiB
Dart
119 lines
2.9 KiB
Dart
import 'package:flutter/material.dart';
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/// create by 张风捷特烈 on 2020/6/3
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/// contact me by email 1981462002@qq.com
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/// 说明:
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// {
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// "widgetId": 285,
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// "name": 'CustomSingleChildLayout的偏移使用',
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// "priority": 2,
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// "subtitle":
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// "可以利用代理的偏移能力，对子组件进行偏移定位。",
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// }
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class OffSetWidgetDemo extends StatelessWidget {
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final data = [
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{
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'offset': Offset(20, 20),
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'direction': Direction.topLeft,
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},
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{
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'offset': Offset(20, -15),
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'direction': Direction.topRight,
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},
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{
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'offset': Offset(-15, 20),
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'direction': Direction.bottomLeft,
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},
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{
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'offset': Offset(-15, 20),
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'direction': Direction.bottomLeft,
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},
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{
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'offset': Offset(15, 20),
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'direction': Direction.bottomLeft,
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},
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{
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'offset': Offset(-15, -15),
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'direction': Direction.topRight,
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},
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];
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@override
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Widget build(BuildContext context) {
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return Wrap(
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spacing: 20,
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runSpacing: 20,
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children: data
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.map((e) => Container(
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width: 150,
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height: 100,
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alignment: Alignment.topRight,
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color: Colors.grey.withAlpha(11),
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child: OffSetWidget(
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offset: e['offset'],
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direction: e['direction'],
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child: Icon(
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Icons.android,
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size: 30,
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color: Colors.green,
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),
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)))
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.toList());
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}
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}
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class OffSetWidget extends StatelessWidget {
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final Offset offset;
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final Widget child;
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final Direction direction;
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OffSetWidget(
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{this.offset = Offset.zero,
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this.child,
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this.direction = Direction.topLeft});
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@override
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Widget build(BuildContext context) {
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return CustomSingleChildLayout(
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delegate: _OffSetDelegate(offset: offset, direction: direction),
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child: child,
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);
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}
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}
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enum Direction { topLeft, topRight, bottomLeft, bottomRight }
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class _OffSetDelegate extends SingleChildLayoutDelegate {
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final Offset offset;
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final Direction direction;
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_OffSetDelegate(
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{this.offset = Offset.zero, this.direction = Direction.topLeft});
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@override
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bool shouldRelayout(_OffSetDelegate oldDelegate) =>
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offset != oldDelegate.offset;
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@override
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Offset getPositionForChild(Size size, Size childSize) {
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var w = size.width;
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var h = size.height;
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var wc = childSize.width;
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var hc = childSize.height;
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switch (direction) {
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case Direction.topLeft:
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return offset;
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case Direction.topRight:
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return offset.translate(w - wc - offset.dx * 2, 0);
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case Direction.bottomLeft:
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return offset.translate(0, h - hc - offset.dy * 2);
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case Direction.bottomRight:
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return offset.translate(w - wc - offset.dx * 2, h - hc - offset.dy * 2);
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}
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return offset;
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}
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}
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