APP运行显示黑屏，console中报The app delegate must implement the window property if it wants to use a main storyboard file.
解决办法：
1、 在AppDelegate.h文件中添加代码：
@property (strong, nonatomic) UIWindow * window;
AppDelegate.h
2、在AppDelegate.m文件中添加代码：
@synthesize window = _window;
AppDelegate.m
