UGUI血条

using System.Collections;
using System.Collections.Generic;
using UnityEngine;
using UnityEngine.UI;

public class HealthBar : MonoBehaviour {

public float HealthPoint
{
get
{
return m_Slider.value;
}
set
{
m_Slider.value = value;
}
}

public float MaxHealthPoint
{
get
{
return m_Slider.maxValue;
}
set
{
m_Slider.maxValue = value;
}
}

void Start()
{
if (Canvas == null) Debug.LogError("Please set a canvas for health bar.");
m_SliderRectTransform = gameObject.GetComponent<Slider>().transform as RectTransform;
//transform.parent = Canvas.transform;
transform.SetParent(Canvas.transform);
// 获取物体高度 https://blog.csdn.net/haobaworenle/article/details/53898221
m_ObjectHeight = FollowTarget.GetComponent<MeshRenderer>().bounds.size.y;
Debug.Log("object height." + m_ObjectHeight);
m_Slider = gameObject.GetComponent<Slider>();
}

void Update()
{
UpdateHealthBarPosition();
}

private void LateUpdate()
{
UpdateHealthBarColor();
}

void UpdateHealthBarPosition()
{
Vector3 worldPosition = new Vector3(FollowTarget.transform.position.x,
FollowTarget.transform.position.y + m_ObjectHeight, FollowTarget.transform.position.z);
// 根据NPC头顶的3D坐标换算成它在2D屏幕中的坐标
Vector2 position = Camera.main.WorldToScreenPoint(worldPosition);
m_SliderRectTransform.position = position;
}

void UpdateHealthBarColor()
{
if (m_Slider.value < m_Slider.maxValue * 0.5f)
{
m_FillImage.color = Color.red;
}
else
{
m_FillImage.color = Color.green;
}
if (m_Slider.value <= 0)
{
Debug.Log(gameObject.name + " is dead");
}
}

public Canvas Canvas;
public GameObject FollowTarget; // 血条跟踪的对象
private RectTransform m_SliderRectTransform;
private Slider m_Slider;

[SerializeField] private Image m_FillImage;
private float m_ObjectHeight;