I checked the document and OVRInput.cs of Oculus Integration. So I can get the status when pressing the button on controller by using "Get()", "GetDown()" and "GetUp()".
Debug.Log(OVRInput.Get(OVRInput.RawButton.B));
However, I noticed that when you touch but do not press the button, the controller still can check this status and change the animation of the virtual hand.
How could I detect this status of the button?