The iOS 8.1 simulator runtime is not available error in Xcode 6.1解决方案

今天用Xcode6.1运行代码突然出了这么一个报错:"The iOS 8.1 simulator runtime is not available error in Xcode 6.1"系统给出的解决方案是Download the ios8.1 simulator runtime from the Downloads section in Xcode‘s Preference。其实根本没有用，因为去了Xcode的Preference里面找到downloads那个section,里面能下载的也只是一个7.1的simulator。今天用Xcode6.1运行代码突然出了这么一个报错:"The iOS 8.1 simulato