Unity多线程管理

游戏中我们有许多地方还是有需求要开启多线程，例如下载文件，解压文件等操作，我们需要在Unity下使用
多线程，那我们如何能更方便的管理多线程呢？

目前主要需要解决一下几个问题：

1. 统一开启子线程，防止多线程滥用
2. 子线程中如何回调主线程

我目前的解决方案

• 所有需要异步处理的任务，都继承AsyncTask。
• AsyncTask封装了执行过程，方便对任务的控制。
• 所有需要回调主线程的地方，统一添加Action。由主线程逐帧调用

代码如下：

using System;
using System.Collections;
using System.Collections.Generic;
using System.Threading;
using UnityEngine;
using LuaFramework;

/// <summary>
/// 异步任务，交给子线程执行
/// </summary>
public abstract class AsyncTask
{
    // multiThreadMgr
    protected MultiThreadManager MultiThreadMgr {
        get {
            return AppFacade.Instance.GetManager<MultiThreadManager> (ManagerName.MultiThread);
        }
    } 

    /// <summary>
    /// 执行任务
    /// </summary>
    public void Execute() {
        try {
            Run();
        } finally {
            MultiThreadMgr.FinishTask (this);
        }
    }

    /// <summary>
    /// 关闭执行
    /// </summary>
    public abstract void Close ();

    /// <summary>
    /// 开始运行
    /// </summary>
    public abstract void Run ();
}

/// <summary>
/// 多线程管理器
/// </summary>
public class MultiThreadManager : Manager
{
    // 需要在主线程执行的操作
    static List<Action> actions = new List<Action> ();
    static List<Action> runningActions = new List<Action> ();
    static object obj = new object();

    // 异步任务队列
    static List<AsyncTask> taskList = new List<AsyncTask> ();

    /// <summary>
    /// 在主线程中执行
    /// </summary>
    /// <param name="action">Action.</param>
    public void RunOnMainThread (Action action)
    {
        lock (obj) {
            actions.Add (action);
        }
    }

    /// <summary>
    /// 添加异步任务
    /// </summary>
    /// <param name="runnable">Runnable.</param>
    public void AddAsyncTask (AsyncTask runnable)
    {
        Debug.Log("AddTask:" + runnable.ToString());
        taskList.Add (runnable);
        Thread thread = new Thread (runnable.Execute);
        thread.IsBackground = true;
        thread.Start ();
    }

    /// <summary>
    /// 完成异步任务
    /// </summary>
    /// <param name="runnable">Runnable.</param>
    public void FinishTask (AsyncTask runnable)
    {
        taskList.Remove (runnable);
        Debug.Log ("RemoveTask:" + runnable.ToString () + "," + taskList.Count);
    }

    /// <summary>
    /// 主线程更新
    /// </summary>
    void Update ()
    {
        lock (obj) {
            runningActions.Clear ();
            runningActions.AddRange (actions);
            actions.Clear ();
        }

        // 处理主线程事件
        if (runningActions.Count > 0) {
            foreach(Action action in runningActions) {
                action ();
            }
        }
        runningActions.Clear ();
    }

    void OnDestroy() {
        for (int i = 0; i < taskList.Count; i++) {
            taskList [i].Close ();
        }
    }
}