Unity自定义定时器

using UnityEngine;
using System.Collections;

public class Timer : MonoBehaviour
{
private float _time;
private float _lastTime;
private bool _isStart;

public float time
{
get { return _time; }
}

public bool isStart
{
get { return _isStart; }
}

// Use this for initialization
void Start()
{
_time = 0;
_lastTime = 0;
_isStart = false;
}

// Update is called once per frame
void Update()
{
if (_isStart)
{
_time = Time.time - _lastTime;
//Debug.Log("Time:" + _time);
}
}

public void RestartTimer()
{
_lastTime = Time.time;
_isStart = true;
Debug.Log("RestartTimer");
}

public void StopTimer()
{
if (_isStart)
{
_lastTime = 0;
_time = 0;
_isStart = false;
Debug.Log("StopTimer");
}
}

public void PauseTimer()
{
if (_isStart)
{
_lastTime = _time;
_isStart = false;
Debug.Log("PauseTimer");
}
}

public void StartTimer()
{
if (!_isStart)
{
_lastTime = Time.time - time;
_isStart = true;
Debug.Log("StartTimer");
}
}

#region //for test
//void OnGUI()
//{
//    if (GUI.Button(new Rect(0, 0, 200, 200), "Start"))
//    {
//        StartTimer();
//    }
//    if (GUI.Button(new Rect(200, 0, 200, 200), "Pause"))
//    {
//        PauseTimer();
//    }
//    if (GUI.Button(new Rect(400, 0, 200, 200), "Stop"))
//    {
//        StopTimer();
//    }
//    if (GUI.Button(new Rect(600, 0, 200, 200), "Restart"))
//    {
//        RestartTimer();
//    }
//}
#endregion
}