anime_rect(use animation.dart)

https://github.com/kyorohiro/hello_skyengine/blob/master/anime_rect_1

// following code is checked in 2016/01/13
import 'package:flutter/widgets.dart';
import 'package:flutter/services.dart';
import 'package:flutter/rendering.dart';
import 'package:flutter/scheduler.dart';
import 'dart:math';
import 'dart:async';
void main() {
runApp(new DrawRectWidget()..anime());
}
class DrawRectWidget extends OneChildRenderObjectWidget {
double angle = 0.0;
DrawRectObject o = new DrawRectObject();
RenderObject createRenderObject() {
return o;
}
int prevTimeStamp = 0;
void anime() {
//
// 2016/1/13 add following code
// Scheduller == null situation
if(Scheduler.instance == null) {
new Future.delayed(new Duration(seconds: 1)).then((_){
anime();
});
return;
}
//
Scheduler.instance.scheduleFrameCallback((Duration timeStamp) {
print("${timeStamp.inMilliseconds-prevTimeStamp}");
prevTimeStamp = timeStamp.inMilliseconds;
o.x = 100 * cos(PI * angle / 180.0) + 100.0;
o.y = 100 * sin(PI * angle / 180.0) + 100.0;
angle++;
o.markNeedsPaint();
anime();
});
}
}
class DrawRectObject extends RenderBox {
double x = 50.0;
double y = 50.0;
@override
void performLayout() {
size = constraints.biggest;
}
void paint(PaintingContext context, Offset offset) {
Paint p = new Paint();
p.color = new Color.fromARGB(0xff, 0xff, 0xff, 0xff);
Rect r = new Rect.fromLTWH(x, y, 25.0, 25.0);
context.canvas.drawRect(r, p);
}
}