// Copyright 2016 The Chromium Authors. All rights reserved. // Use of this source code is governed by a BSD-style license that can be // found in the LICENSE file. // This example shows how to use the Cassowary autolayout system with widgets. import 'package:cassowary/cassowary.dart' as al; import 'package:flutter/widgets.dart'; class _MyAutoLayoutDelegate extends AutoLayoutDelegate { AutoLayoutRect p1 = new AutoLayoutRect(); AutoLayoutRect p2 = new AutoLayoutRect(); AutoLayoutRect p3 = new AutoLayoutRect(); AutoLayoutRect p4 = new AutoLayoutRect(); List<al.Constraint> getConstraints(AutoLayoutRect parent) { return <al.Constraint>[ // Sum of widths of each box must be equal to that of the container parent.width.equals(p1.width + p2.width + p3.width), // The boxes must be stacked left to right p1.right <= p2.left, p2.right <= p3.left, // The widths of the first and the third boxes should be equal p1.width.equals(p3.width), // The width of the second box should be twice as much as that of the first // and third p1.width.equals(p2.width * al.cm(2.0)), // The height of the three boxes should be equal to that of the container p1.height.equals(p2.height), p2.height.equals(p3.height), p3.height.equals(parent.height), // The fourth box should be half as wide as the second and must be attached // to the right edge of the same (by its center) p4.width.equals(p2.width / al.cm(2.0)), p4.height.equals(al.cm(50.0)), p4.horizontalCenter.equals(p2.right), p4.verticalCenter.equals(p2.height / al.cm(2.0)), ]; } bool shouldUpdateConstraints(_MyAutoLayoutDelegate oldDelegate) => true; } class ColoredBoxes extends StatefulWidget { _ColoredBoxesState createState() => new _ColoredBoxesState(); } class _ColoredBoxesState extends State<ColoredBoxes> { final _MyAutoLayoutDelegate delegate = new _MyAutoLayoutDelegate(); Widget build(BuildContext context) { return new AutoLayout( delegate: delegate, children: <Widget>[ new AutoLayoutChild( rect: delegate.p1, child: new DecoratedBox( decoration: new BoxDecoration(backgroundColor: const Color(0xFFFF0000)) ) ), new AutoLayoutChild( rect: delegate.p2, child: new DecoratedBox( decoration: new BoxDecoration(backgroundColor: const Color(0xFF00FF00)) ) ), new AutoLayoutChild( rect: delegate.p3, child: new DecoratedBox( decoration: new BoxDecoration(backgroundColor: const Color(0xFF0000FF)) ) ), new AutoLayoutChild( rect: delegate.p4, child: new DecoratedBox( decoration: new BoxDecoration(backgroundColor: const Color(0xFFFFFFFF)) ) ), ] ); } } void main() { runApp(new ColoredBoxes()); }