Development cannot be enabled while your device is locked.

问题：Development cannot be enabled while your device is locked.

分析缘由：因为第一次链接MAC时，在iOS设备上点击了"不信任"选项，因此XCode 8不能访问手机，因此才出现这个问题

解决方法：

英文好的同窗，能够看到原文章

http://stackoverflow.com/questions/26791477/xcode-device-locked-when-iphone-is-unlocked

如下我说下方法

这是APPLE官网的解释

https://support.apple.com/en-us/HT202778

重点是这段

Change your settings for trusted computers

Your iOS device remembers the computers you've chosen to trust.

If you don't want to trust a computer or other device anymore, change the privacy settings on your iPhone, iPad, or iPod touch: In iOS 8 or later, tap Settings > General > Reset > Reset Location & Privacy. Now when you connect to formerly trusted computers, the Trust alert will ask you whether you trust that computer. 

意思是说重置隐私设置

点击 设置 --> 通用 --> 重置  --> 重置位置和隐私 

而后关闭xcode 8, 拔掉数据线，重启xocde 8开启项目， 从新插上数据线，此时手机上会显示mac与手机设备的链接访问权限，选择“信任”，

大功告成了~~~