多次未占用重新排序方法

        private int messageIndex = -1;

        private static Dictionary<int, bool> indexMap;
        private static int GetAvailableAlertIndex()
        {
            if (indexMap == null)
            {
                indexMap = new Dictionary<int, bool>();
            }
            int maxNum = GetMaxmumAlerts();
            for (int i = 0; i < maxNum; i++)
            {
                if (indexMap.ContainsKey(i))
                {
                    if (indexMap[i])
                    {
                        indexMap[i] = false;
                        return i;
                    }
                }
                else
                {
                    indexMap.Add(i, false);
                    return i;
                }
            }
            return -1;
        }
        private void ResetIndex()
        {
            if (messageIndex == -1)
                return;
            System.Diagnostics.Debug.Assert(indexMap != null);
            if (indexMap != null)
            {
                if (indexMap.ContainsKey(messageIndex))
                {
                    indexMap[messageIndex] = true;
                }
            }           
            messageIndex = -1;
        }