Unity UI跟随物体

图上是体力条跟随着主角，主角左移，体力条就跟着左移。

首先我们需要知道主角单位对于屏幕

PlayerScreen = Camera.main.WorldToScreenPoint(Player.transform.position);

然后需要知道一开始UI和主角得屏幕相对位置之间得距离参数，利用这个参数就能使UI一直跟着主角。

offest.x = PlayerScreen.x - transform.position.x;
offest.z = PlayerScreen.z - transform.position.z;
offest.y = transform.position.y;

Update里面一直获取主角对于屏幕的相对位置，然后在进行相减，就可以一直保持了。

 void Update()
    {
            PlayerScreen = Camera.main.WorldToScreenPoint(Player.transform.position);
            transform.position = PlayerScreen;
            transform.position = new Vector2(transform.position.x - offest.x, offest.y);
    }

不过我发现了，如果我在编辑器里面全屏运行，会出现UI靠的很近，我觉得非常奇怪，因为代码已经提前计算好了他们之间的距离，后面也是根据这个距离用来保持。

于是我发现，是因为一开始屏幕是小屏化的，Start一开始获取的offest差值是小屏时候的距离差，所以放大之后，UI就会靠的非常近，所以我就一时偷懒，直接一个协程，让他慢一秒在开始获取。

  IEnumerator Wait() 
   {
       yield return new WaitForSeconds(1f);
       Player = GameObject.FindGameObjectWithTag("Player").transform;
       PlayerScreen = Camera.main.WorldToScreenPoint(Player.transform.position);
       offest.x = PlayerScreen.x - transform.position.x;
       offest.z = PlayerScreen.z - transform.position.z;
       offest.y = transform.position.y;
       IsRun = true;
   }

最后代码如下：

public class UIFollowShow : MonoBehaviour
{
    private Transform Player;
    private Vector3 offest;
    private Vector3 PlayerScreen;
    private bool IsRun;

    // Start is called before the first frame update
    void Awake()
    {
        StartCoroutine(Wait());
    }

    // Update is called once per frame
    void Update()
    {
        if (IsRun)
        {
            PlayerScreen = Camera.main.WorldToScreenPoint(Player.transform.position);
            transform.position = PlayerScreen;
            transform.position = new Vector2(transform.position.x - offest.x, offest.y);
        }
    }

    IEnumerator Wait() 
    {
        yield return new WaitForSeconds(1f);
        Player = GameObject.FindGameObjectWithTag("Player").transform;
        PlayerScreen = Camera.main.WorldToScreenPoint(Player.transform.position);
        offest.x = PlayerScreen.x - transform.position.x;
        offest.z = PlayerScreen.z - transform.position.z;
        offest.y = transform.position.y;
        IsRun = true;
    }
}