interface in UnityEngine.Experimental.UIElements
切换到手册控件接口，这些控件保存值并且可以在用户输入更改值时发出通知。
| value | 控件保存的值。 |
| OnValueChanged | Registers this callback to receive ChangeEvent<T> when value is changed by user input. |
| RemoveOnValueChanged | Unregisters this callback from receiving ChangeEvent<T> when value is changed by user input. |
| SetValueWithoutNotify | Set the value and, even if different, does not notify registers callbacks with a ChangeEvent<T> |