Unity 2D物体左右移动脚本(鼠标触摸+键盘)

using UnityEngine;
using System.Collections;

public class Paddle : MonoBehaviour
{
    void Update()
    {
        if (GameManager.Instance.currentState == GameState.Playing && GameManager.Instance != null)
        {
            //鼠标或触摸
            if (Input.GetMouseButton(0))
            {
                //Create a ray from camera to playfield
                Ray mouseRay = Camera.main.ScreenPointToRay(Input.mousePosition);
                Plane p = new Plane(Vector3.up, transform.position);

                //Shoot the ray to know where the click/tap found place in 3D
                float distance;
                if (p.Raycast(mouseRay, out distance))
                {
                    //Use current position as starting point
                    Vector3 position = transform.position;
                    //The player can only move the paddle in the x axis, so don't use the y and z
                    position.x = mouseRay.GetPoint(distance).x; //GetPoint gives us the position in 3D
                                                                //Apply the new position
                    transform.position = position;
                }
                else
                {
                    //The ray missed
                }
            }

            // 键盘
            else if (Input.GetKey(KeyCode.A) || Input.GetKey(KeyCode.LeftArrow))
            {
                //Use current position as starting point
                Vector3 position = transform.position;
                position.x = position.x - Time.deltaTime * 50;
                transform.position = position;


            }
            else if (Input.GetKey(KeyCode.D) || Input.GetKey(KeyCode.RightArrow))
            {
                //Use current position as starting point
                Vector3 position = transform.position;
                position.x = position.x + Time.deltaTime * 50;
                transform.position = position;
            }
        }
        
        //Make sure the paddle stays inside the level
        float freedom = 19.25F;
        Vector3 limitedPosition = transform.position;
        if (Mathf.Abs(limitedPosition.x) > freedom)
        {
            //Paddle is outside the level so move it back in
            limitedPosition.x = Mathf.Clamp(transform.position.x, -freedom, freedom);
            transform.position = limitedPosition;
        }
    }
}