ios获取屏幕分辨率

1、得到当前屏幕的尺寸：

CGRect rect_screen = [[UIScreenmainScreen]bounds];

    CGSize size_screen = rect_screen.size;

2、获得scale：

CGFloat scale_screen = [UIScreen mainScreen].scale;

3、获取分辨率

CGFloat width = size_screen.width*scale_screen;

CGFloat height = size_screen.height*scale_screen;