iPhone各种尺寸
iPhone 6 Plus 736x414 points 2208x1242 pixels 3x scale 1920x1080 physical pixels 401 physical ppi 5.5"
iPhone 6 667x375 points 1334x750 pixels 2x scale 1334x750 physical pixels 326 physical ppi 4.7"
iPhone 5 568x320 points 1136x640 pixels 2x scale 1136x640 physical pixels 326 physical ppi 4.0"
iPhone 4 480x320 points 960x640 pixels 2x scale 960x640 physical pixels 326 physical ppi 3.5"
iPhone 3GS 480x320 points 480x320 pixels 1x scale 480x320 physical pixels 163 physical ppi 3.5”
@property (nonatomic, weak) UIActivityIndicatorView *loadingView;