UIView

how to add line to UIView?

UIView * separator = [[UIView alloc] initWithFrame:CGRectMake(20, 104, 320, (1.0 / [UIScreen mainScreen].scale) / 2)];
    separator.backgroundColor = [UIColor colorWithWhite:0.7 alpha:1];
    [self.view addSubview:separator];

how to make the line exactly 1px for both normal iOS device as well as retina display device?

CGFloat scaleOfMainScreen = [UIScreen mainScreen].scale;
    CGFloat alwaysOnePixelInPointUnits = 1.0/scaleOfMainScreen;

    UIView * separator = [[UIView alloc] initWithFrame:CGRectMake(20, 40, 300, alwaysOnePixelInPointUnits)];
    separator.backgroundColor = [UIColor colorWithWhite:1 alpha:0.2];
    [self.view addSubview:separator];

dismiss keyboard when user taps other area:

- (void)touchesBegan:(NSSet *)touches withEvent:(UIEvent *)event {
    for (UIView * txt in self.view.subviews){
        if ([txt isKindOfClass:[UITextField class]] && [txt isFirstResponder]) {
            [txt resignFirstResponder];
        }
    }
}

/*OR*/

- (void)touchesBegan:(NSSet *)touches withEvent:(UIEvent *)event {
    [self.view endEditing:YES];
}

reference

how to set view background image?

self.view.backgroundColor = [UIColor colorWithPatternImage:[UIImage imageNamed:@"randomgrey.png"]];

how to stretch the image if size not fit?

    UIGraphicsBeginImageContext(self.view.frame.size);
    [[UIImage imageNamed:@"chat_blur_default9"] drawInRect:self.view.bounds];
    UIImage *image = UIGraphicsGetImageFromCurrentImageContext();
    UIGraphicsEndImageContext();
    self.view.backgroundColor = [UIColor colorWithPatternImage:image];

how to add uiview programmingly ?

UIView *cv = [[UIView alloc]initWithFrame:CGRectMake(0, self.view.frame.size.height, 320, 216)]; //creat an instance of your custom view
    cv.backgroundColor = [UIColor colorWithRed:0.941 green:0.941 blue:0.941 alpha:1];
    [self.view addSubview:cv]; // add to your main view