#define SINGLE_LINE_WIDTH (1 / [UIScreen mainScreen].scale)
#define SINGLE_LINE_ADJUST_OFFSET ((1 / [UIScreen mainScreen].scale) / 2)
@interface ViewController ()
@end
@implementation ViewController
- (void)viewDidLoad {
[super viewDidLoad];
NSLog(@"%f", [[UIScreen mainScreen]scale]);
UIView *lineview = [[UIView alloc] initWithFrame:CGRectMake(10- SINGLE_LINE_ADJUST_OFFSET, 100, SINGLE_LINE_WIDTH, 200)];
lineview.backgroundColor=[UIColor redColor];
[self.view addSubview:lineview];
}