关于Tween的几个注意事项

以下几点下面的范例中都有体现：

1. 运行时创建Tween 的话不要忘了将其加入节点树

2. 如果要给一个Tween行为注册回调函数，注册一次就可以

3. Tween行为时临时的，执行完毕以后不再保存，所以下次start前要重新定义

extends Node
var tween : Tween
func _ready():
	tween = Tween.new()
	add_child(tween)#加入节点树
	tween.connect("tween_all_completed",self,"tween_all_completed")
	#tween.interpolate_property(self,"rotation_degrees",Vector3(0,init_degree,0),Vector3(0,final_degree,0),duration,Tween.TRANS_LINEAR,Tween.EASE_IN)
func play():
	#tween.connect("tween_all_completed",self,"tween_all_completed")
	tween.interpolate_property(self,"rotation_degrees",Vector3(0,0,0),Vector3(0,90,0),0.2,Tween.TRANS_LINEAR,Tween.EASE_IN)
	tween.start()