1、需求
一般来说，对于下载队列的需求一般会有一下几点：
A、基本的增删改查
B、插入优先级
C、打断当前下载，优先下载要用
D、可能的其他特殊需求，比如某一类下载需要按顺序下，因此新增的优先下载项就不是插入下载池的最前面，而是需要加在该类下载的最后，其他下载之前。

2、设计
A、选用list作为下载池队列，便于自由管理
B、基本的增删改查的实现

    /// <summary>
    /// 加入下载池最后
    /// </summary>
    public void AddDownloadPool(DownLoadPoolItem item)
    {
        if (HasDownloadItem(item))
            return;
        Instance.downloadQueue.Add(item);
    }
    /// <summary>
    /// 加入下载池最后
    /// </summary>
    public void AddDownloadPool(List<DownLoadPoolItem> items)
    {
        for (int i = 0; i < items.Count; i++)
        {
            DownLoadPoolItem _item = Instance.downloadQueue.Find((x) => x.itemName == items[i].itemName);
            if (_item != null)
            {
                Instance.downloadQueue.Remove(_item);
                items[i] = _item;
            }
        }
        Instance.downloadQueue.AddRange(items);
    }
    /// <summary>
    /// 插入下载池，默认插入池的最前面
    /// </summary>
    public void InsetDownloadPool(DownLoadPoolItem item, int index = 0)
    {
        //如果第一个已经是item，不需要插入直接return
        if (Instance.downloadQueue.Count > 0 && Instance.downloadQueue[0].itemName == item.itemName)
            return;
        DownLoadPoolItem _item = Instance.downloadQueue.Find((x) => x.itemName == item.itemName);
        DebugBuild.Log(item.itemName + "-------------------插入静默下载队列----1个--------------" + (_item == null));
        if (_item != null)
        {
            Instance.downloadQueue.Remove(_item);
        }
        Instance.downloadQueue.Insert(index, item);
    }
    /// <summary>
    /// 插入下载池，默认插入池的最前面
    /// </summary>
    public void InsetDownloadPool(List<DownLoadPoolItem> items, int index = 0)
    {
        for (int i = 0; i < items.Count; i++)
        {
            DownLoadPoolItem _item = Instance.downloadQueue.Find((x) => x.itemName == items[i].itemName);
            DebugBuild.Log(items[i].itemName + "-------------------插入静默下载队列-----多个-------------" + (_item == null));
            if (_item != null)
            {
                Instance.downloadQueue.Remove(_item);
                items[i] = _item;
            }
        }
        Instance.downloadQueue.InsertRange(index, items);
    }
    public static bool HasDownloadItem(DownLoadPoolItem item)
    {
        return Instance.downloadQueue.Find((x) => x.itemName == item.itemName) != null;
    }
    public static bool HasDownloadItem(string fileName)
    {
        return Instance.downloadQueue.Find((x) => x.filename == fileName) != null;
    }
    /// <summary>
    /// 根据文件名移除池中对应下载
    /// </summary>
    /// <param name="filename"></param>
    public static void DeleteDownloadPool(string filename)
    {
        var item = Instance.downloadQueue.Find((x) => x.filename == filename);
        if (item == null)
            return;
        Instance.downloadQueue.Remove(item);
    }

C、制定基本下载流程

Paste_Image.png

D、插入优先下载是否需要打断当前下载
当前下载存起来，便于管理

    /// <summary>
    /// 设置当前下载，并从下载池中移除
    /// </summary>
    public static DownLoadPoolItem SetNowDownLoadItem()
    {
        if (Instance.downloadQueue.Count == 0)
        {
            DebugBuild.LogError("--------------------SetNowDownLoadItem----------------------下载池无下载项---------------------------");
            return null;
        }
        if (!GetNowDownLoadIsNull)
        {
            DebugBuild.LogError("--------------------设置当前下载----------------------当前有下载请先打断---------------------------");
            return null;
        }
        nowDownLoadItem = Instance.downloadQueue[0];
        DebugBuild.Log("---------------------------设置当前下载-------------------------"+ nowDownLoadItem.itemName);
        Instance.downloadQueue.RemoveAt(0);
        return nowDownLoadItem;
    }
    /// <summary>
    /// 设置当前下载被打断，回到下载池，并设置当前为null
    /// </summary>
    public static void SetNowItemBackPool()
    {
        //如果当前有正在下载，则加到下载池第一个
        if (!GetNowDownLoadIsNull)
        {
            DebugBuild.Log("-------------------------------------当前下载被打断，回到下载池-------------------------------------------"+ nowDownLoadItem.itemName);
            Instance.InsetDownloadPool(nowDownLoadItem);
            nowDownLoadItem = null;
        }
    }

E、基本下载流程测试
F、特殊需求添加