崩溃问题：iOS9 This application is modifying the autolayout engine from a background thread, which

总结：通知、更新UI尽量放到主线程中之行，以防无法无法预见到问题出现

以前在Xcode7之间项目没有问题，但是使用Xcode7后 突然不好使了，This application is modifying the autolayout engine from a background thread, which can lead to engi....

查了查资料 把需要更新UI的放在的主线程就好了。（不懂什么原理但暂时解决的问题）

链接 http://stackoverflow.com/questions/31951704/this-application-is-modifying-the-autolayout-engine-from-a-background-thread-wh