效果如下：

您只需要控制此对象进行激活，将对象设置为：gameObject.SetActive(true);即可实现此次效果

代码如下：

public class StartShowRun : MonoBehaviour
{

    Transform _localTransfrom;
    Vector3 _localScale;


    public AnimationCurve curve;//可编辑动画曲线
    [Range(0.1f, 6)]
    public float durationTime = 6;

    int _past = 0;

    float x, t;

    void Awake()
    {
        _localScale = this.transform.localScale;
        _localTransfrom = this.GetComponent<RectTransform>();
        this.transform.localScale = new Vector3(0.01f, 0.01f, 1);
    }

    //激活调用
    private void OnEnable()
    {
        _past = 0;
        t = 0;
        x = 0;
    }

    // Update is called once per frame
    void Update()
    {
        if (_past == 0)
        {

            t = x / durationTime;
            _localTransfrom.localScale = Vector3.Lerp(this.transform.localScale, _localScale, curve.Evaluate(t));
            x += Time.deltaTime;
            if (this.transform.localScale.x >= 0.998f)
            {
                _past = -1;//开始缩小
                t = 0;
                x = 0;
            }
        }
        if (_past == -1)
        {

            t = x / durationTime;
            _localTransfrom.localScale = Vector3.Lerp(this.transform.localScale, new Vector3(0.01f, 0.01f, 1), curve.Evaluate(t));
            x += Time.deltaTime;

            if (this.transform.localScale.y <= 0.1f)
            {
                _past = 1;//代表结束
                transform.gameObject.SetActive(false);
            }
        }

    }
}