https://github.com/kyorohiro/hello_skyengine/tree/master/touch_event
//// following code is checked in 2016/01/13// from 2015/11/07 need override// need bool hitTest(HitTestResult result, {Point position})//import 'package:flutter/widgets.dart';import 'package:flutter/rendering.dart';void main() {runApp(new DrawRectWidget());}class DrawRectWidget extends OneChildRenderObjectWidget {RenderObject createRenderObject() {return new DrawRectObject();}}class DrawRectObject extends RenderBox {double x = 100.0;double y = 100.0;@overridebool hitTest(HitTestResult result, {Point position}) {result.add(new BoxHitTestEntry(this, position));return true;}@overridevoid performLayout() {size = constraints.biggest;}@overridevoid paint(PaintingContext context, Offset offset) {Paint p = new Paint();p.color = new Color.fromARGB(0xff, 0xff, 0xff, 0xff);Rect r = new Rect.fromLTWH(x - 50.0, y - 50.0, 100.0, 100.0);context.canvas.drawRect(r, p);}@overridevoid handleEvent(PointerEvent event, HitTestEntry entry) {if (entry is BoxHitTestEntry) {if (event is PointerDownEvent) {x = entry.localPosition.x;y = entry.localPosition.y;} else {x = event.position.x;y = event.position.y;}markNeedsPaint();}}}