Question

This one:

UIView *view = [[UIView alloc] initWithFrame:CGRectMake(x, y, width, 1)];
view.backgroundColor = [UIColor whiteColor];
view.alpha = 0.1;

or this one:

UIView *view = [[UIView alloc] initWithFrame:CGRectMake(x, y, width, 1)];
view.backgroundColor = [UIColor colorWithWhite:1.0 alpha:0.1];

or is there any third alternative? Using a UIImageView with image? Doing custom drawing with CoreGraphics? What is supposed to be fastest?

Answer 1

The fastest way would be to create a CALayer. Using this will allow you to easily alter its color/opacity if needed.

CALayer *line = [CALayer new];
line.frame = CGRectMake(x, y, width, 1.0);
line.backgroundColor = [[UIColor whiteColor] colorWithAlphaComponent:0.1].CGColor;
[someView.layer addSublayer:line];

If you want to draw a line right onto an existing view and have it stay there with no altering you can add the following code to the drawRect: method of the existing view:

CGContextRef context = UIGraphicsGetCurrentContext();
CGContextSetStrokeColorWithColor(context, [[UIColor whiteColor] colorWithAlphaComponent:0.1].CGColor);
CGContextSetLineWidth(context, 1.0);
CGContextMoveToPoint(context, x, y);
CGContextAddLineToPoint(context, x + width, y);
CGContextStrokePath(context);