多屏幕适配

两个方法中的区别

NSLog(@"[UIScreen mainScreen] bounds].size.width%f",[[UIScreen mainScreen] bounds].size.width);

打印出来的结果是

2016-07-22 17:00:02.084 huibamTracking[22437:373638] [UIScreen mainScreen] bounds].size.width320.000000

第二个

NSLog(@"[UIScreen mainScreen] bounds].size.width%f",self.view.frame.size.width);

2016-07-22 17:00:02.084 huibamTracking[22437:373638] [UIScreen mainScreen] bounds].size.width375.000000