| // Copyright 2015 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. |
| |
| import 'package:flutter/rendering.dart'; |
| import 'package:flutter/widgets.dart'; |
| |
| class RenderDots extends RenderConstrainedBox { |
| RenderDots() : super(additionalConstraints: const BoxConstraints.expand()); |
| |
| // Makes this render box hittable so that we'll get pointer events. |
| @override |
| bool hitTestSelf(Offset position) => true; |
| |
| final Map<int, Offset> _dots = <int, Offset>{}; |
| |
| @override |
| void handleEvent(PointerEvent event, BoxHitTestEntry entry) { |
| if (event is PointerDownEvent || event is PointerMoveEvent) { |
| _dots[event.pointer] = event.position; |
| markNeedsPaint(); |
| } else if (event is PointerUpEvent || event is PointerCancelEvent) { |
| _dots.remove(event.pointer); |
| markNeedsPaint(); |
| } |
| } |
| |
| @override |
| void paint(PaintingContext context, Offset offset) { |
| final Canvas canvas = context.canvas; |
| canvas.drawRect(offset & size, new Paint()..color = const Color(0xFF0000FF)); |
| |
| final Paint paint = new Paint()..color = const Color(0xFF00FF00); |
| for (Offset point in _dots.values) |
| canvas.drawCircle(point, 50.0, paint); |
| |
| super.paint(context, offset); |
| } |
| } |
| |
| class Dots extends SingleChildRenderObjectWidget { |
| const Dots({ Key key, Widget child }) : super(key: key, child: child); |
| |
| @override |
| RenderDots createRenderObject(BuildContext context) => new RenderDots(); |
| } |
| |
| void main() { |
| runApp( |
| const Directionality( |
| textDirection: TextDirection.ltr, |
| child: const Dots( |
| child: const Center( |
| child: const Text('Touch me!'), |
| ), |
| ), |
| ), |
| ); |
| } |