How to draw signature with lines on iPhone screen?

Question

I want to let user draw a signature on iPhone screen, so I add a subclass of UIView and add some code to its 'touchesMoved' method.

-(void)touchesMoved:(NSSet *)touches withEvent:(UIEvent *)event
{
    UITouch *touch = [touches anyObject];
    firstTouch = [touch locationInView:self];

    CGSize mySize = CGSizeMake(5, 5);
    UIGraphicsBeginImageContext(mySize);                                    
    CGContextRef ctx = UIGraphicsGetCurrentContext();                       

    CGContextBeginPath(ctx);                                                
    CGContextSetRGBFillColor(ctx, 1, 0, 0, 1);                              
    CGContextAddRect(ctx, CGRectMake(0, 0, 5, 5));                          
    CGContextFillPath(ctx);                                                 

    UIImage *redRect = UIGraphicsGetImageFromCurrentImageContext();         
    UIGraphicsEndImageContext();                                            

    UIImageView *redRectView = [[UIImageView alloc] initWithImage:redRect]; 
    redRectView.center = CGPointMake(firstTouch.x, firstTouch.y);                               
    [self addSubview:redRectView];                                      

}

I'm drawing it with small rectangles and it turns out to be dot by dot. As it is too ugly, I want to draw the signature with lines. But how to distinguish firstTouch and lastTouch? If I only use 'touchesMoved' method, I can only get one touch point.

Answer 1

As per the UIResponder Class Reference, you will also need to implement
– touchesBegan:withEvent: and
– touchesEnded:withEvent:.
After you implement these methods, you should be able to get enough data to implement a pathing bezier curve or other suitable solution.

[edit] A perhaps better solution would to be to obtain the touches directly from the UIEvent object once your controller receives a
– touchesMoved:withEvent: notification. Also, the GLPaint sample code may also prove helpful.

Answer 2

As the GLPaint sample code may be too complicated for beginners, I find this tutorial. It is simple to learn for most beginners.

Answer 3

Keep in mind that a signature written with one's finger is going to be different than one written with a writing instrument. You may want to re-think what you're using the signature for, and whether it's as binding as you need it to be.