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| import 'package:flutter/material.dart'; | |
| import 'package:flutter/rendering.dart'; | |
| import 'dart:math' as math; | |
| class CustomLayout extends MultiChildRenderObjectWidget { | |
| CustomLayout({ | |
| Key key, | |
| List<Widget> children = const <Widget>[], | |
| }) : super(key: key, children: children); | |
| @override | |
| RenderCustomLayoutBox createRenderObject(BuildContext context) { | |
| return RenderCustomLayoutBox(); | |
| } | |
| } | |
| class RenderCustomLayoutBox extends RenderBox | |
| with ContainerRenderObjectMixin<RenderBox, CustomLayoutParentData>, | |
| RenderBoxContainerDefaultsMixin<RenderBox, CustomLayoutParentData> { | |
| RenderCustomLayoutBox({ | |
| List<RenderBox> children, | |
| }) { | |
| addAll(children); | |
| } | |
| @override | |
| void setupParentData(RenderBox child) { | |
| if (child.parentData is! CustomLayoutParentData) { | |
| child.parentData = CustomLayoutParentData(); | |
| } | |
| } | |
| double _getIntrinsicHeight(double childSize(RenderBox child)) { | |
| double inflexibleSpace = 0.0; | |
| RenderBox child = firstChild; | |
| while (child != null) { | |
| if (child == lastChild) | |
| break; | |
| inflexibleSpace += childSize(child); | |
| final FlexParentData childParentData = child.parentData; | |
| child = childParentData.nextSibling; | |
| } | |
| return inflexibleSpace; | |
| } | |
| double _getIntrinsicWidth(double childSize(RenderBox child)) { | |
| double maxSpace = 0.0; | |
| RenderBox child = firstChild; | |
| while (child != null) { | |
| if (child == lastChild) | |
| break; | |
| maxSpace = math.max(maxSpace, childSize(child)); | |
| final FlexParentData childParentData = child.parentData; | |
| child = childParentData.nextSibling; | |
| } | |
| return maxSpace; | |
| } | |
| @override | |
| double computeMinIntrinsicWidth(double height) { | |
| return _getIntrinsicWidth((RenderBox child) => child.getMinIntrinsicWidth(height)); | |
| } | |
| @override | |
| double computeMaxIntrinsicWidth(double height) { | |
| return _getIntrinsicWidth((RenderBox child) => child.getMaxIntrinsicWidth(height)); | |
| } | |
| @override | |
| double computeMinIntrinsicHeight(double width) { | |
| return _getIntrinsicHeight((RenderBox child) => child.getMinIntrinsicHeight(width)); | |
| } | |
| @override | |
| double computeMaxIntrinsicHeight(double width) { | |
| return _getIntrinsicHeight((RenderBox child) => child.getMaxIntrinsicHeight(width)); | |
| } | |
| @override | |
| void performLayout() { | |
| if (childCount == 0) { | |
| size = constraints.biggest; | |
| assert(size.isFinite); | |
| return; | |
| } | |
| double width = constraints.maxWidth; | |
| double height = 0; | |
| RenderBox child = firstChild; | |
| while (child != null) { | |
| if (child == lastChild) | |
| break; | |
| final CustomLayoutParentData childParentData = child.parentData; | |
| child.layout(BoxConstraints.tightFor(width: width), parentUsesSize: true); | |
| childParentData.offset = Offset(0, height); | |
| final Size childSize = child.size; | |
| width = math.max(width, childSize.width); | |
| height += childSize.height; | |
| child = childParentData.nextSibling; | |
| } | |
| size = Size(width, height); | |
| lastChild.layout(BoxConstraints(maxWidth: width, maxHeight: height), parentUsesSize: true); | |
| final CustomLayoutParentData childParentData = lastChild.parentData; | |
| final double margin = 20; | |
| final double x = size.width - lastChild.size.width - margin; | |
| final double y = height - childParentData.previousSibling.size.height - lastChild.size.height / 2; | |
| childParentData.offset = Offset(x, y); | |
| } | |
| @override | |
| void paint(PaintingContext context, Offset offset) { | |
| defaultPaint(context, offset); | |
| } | |
| @override | |
| bool hitTestChildren(HitTestResult result, { Offset position }) { | |
| return defaultHitTestChildren(result, position: position); | |
| } | |
| } | |
| class CustomLayoutParentData extends ContainerBoxParentData<RenderBox> { | |
| } |
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