Unity实现倒计时组件

// 倒计时
// 倒计时结束的回调

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


[RequireComponent(typeof(Text))]
public class CountDownTime : MonoBehaviour
{
  public int testTime = 15;

  private int _timeLeft = 0;
  private Text _textTimer = null;
  private float _delay = 1;
  private Action _endCallback = null;

  private void Start()
  {
    if (_textTimer == null)
      _textTimer = GetComponent<Text>();

    SetEndCallback(TestEndCallback);
    Begin(testTime, true);
  }

  public void SetEndCallback(Action callback)
  {
    _endCallback = callback;
  }

  public void Begin(int timeLeft, bool isRightNow)
  {
    _timeLeft = timeLeft;
    if (_textTimer == null)
      _textTimer = GetComponent<Text>();

    if (isRightNow) CountDown();
    if (gameObject.activeInHierarchy)
      StartCoroutine(Polling(_delay, CountDown));
  }

  private IEnumerator Polling(float delay, Action voidFunc)
  {
    while (delay > 0)
    {
      voidFunc();

      if (_timeLeft < 0 && _endCallback != null) {
        _endCallback();
        _endCallback = null;
        yield return null;

      }
      yield return new WaitForSeconds(delay);
    }
  }

  private void CountDown()
  {
    if (_timeLeft >= 0)
    {
      TimeSpan ts = new TimeSpan(0, 0, _timeLeft--);
      _textTimer.text = ts.ToString();
    }
    else if (_timeLeft < -1)
    {
      _textTimer.text = _timeLeft.ToString();
    }
  }

  private void TestEndCallback() {
    _textTimer.text = "End!!!";
  }
}