warning：This application is modifying the autolayout engine from a background thread

警告提示：This application is modifying the autolayout engine from a background thread, which can lead to engine corruption and weird crashes. This will cause an exception in a future release.

錯誤緣由：在回調函數中或者後臺線程中更新了UI界面，而UI界面必須是在主界面中才能進行修改

解決辦法：

dispatch_async(dispatch_get_main_queue(), ^{

      <your code>

});