Question

Here is the relevant .m that I am currently using.

- (void)drawRect:(CGRect)rect
{

    [[UIColor redColor] setStroke];
    for (UIBezierPath *_path in pathArray) 
    [_path strokeWithBlendMode:kCGBlendModeNormal alpha:1.0];    


}

#pragma mark -
#pragma mark - Touch Methods


-(void)touchesBegan:(NSSet *)touches withEvent:(UIEvent *)event
{
    myPath=[[UIBezierPath alloc]init];


    NSUserDefaults *ud = [NSUserDefaults standardUserDefaults];

    if([ud objectForKey:@"lineThickness"] == nil) {
        myPath.lineWidth=5;
    }
    else {

        float thicknessFloat = [ud floatForKey:@"lineThickness"];
        myPath.lineWidth= 10. * thicknessFloat;


    }

    UITouch *mytouch=[[touches allObjects] objectAtIndex:0];
    [myPath moveToPoint:[mytouch locationInView:self]];
    [pathArray addObject:myPath];

}
-(void)touchesMoved:(NSSet *)touches withEvent:(UIEvent *)event
{

    UITouch *mytouch=[[touches allObjects] objectAtIndex:0];
    NSUserDefaults *ud = [NSUserDefaults standardUserDefaults];

    if([ud objectForKey:@"lineThickness"] == nil) {
        myPath.lineWidth=5;
    }
    else {

        float thicknessFloat = [ud floatForKey:@"lineThickness"];
        myPath.lineWidth= 10. * thicknessFloat;


    }
    [myPath addLineToPoint:[mytouch locationInView:self]];
    [self setNeedsDisplay];

}

It works great, but since this is tutorial code that is slightly modified by me, I do not know how to approach the problem of wanting to draw lines between two points, and have the framework connect the the points each time a point is added.

Can anyone please point me in a good direction on how to accomplish this please?

Answer 1

The particulars of how to implement this depend upon the effect that you’re looking for. If you’re just tapping on a bunch of points and want to add them to a UIBezierPath you can do something like the following in your view controller:

- (void)touchesBegan:(NSSet *)touches withEvent:(UIEvent *)event
{
    UITouch *mytouch = [[touches allObjects] objectAtIndex:0];
    CGPoint location = [mytouch locationInView:self.view];

    // I'm assuming you have a myPath UIBezierPath which is an ivar which is 
    // initially nil. In that case, we'll check if it's nil and if so, initialize 
    // it, otherwise, it's already been initialized, then we know we're just
    // adding a line segment.

    if (!myPath)
    {
        myPath = [UIBezierPath bezierPath];
        [myPath moveToPoint:location];

        shapeLayer = [[CAShapeLayer alloc] initWithLayer:self.view.layer];
        shapeLayer.lineWidth = 1.0;
        shapeLayer.strokeColor = [UIColor redColor].CGColor;
        shapeLayer.fillColor = [UIColor clearColor].CGColor;

        [self.view.layer addSublayer:shapeLayer];
    }
    else
    {
        [myPath addLineToPoint:location];
        shapeLayer.path = myPath.CGPath;
    }
}

If you wanted something where you can draw with your finger (e.g. dragging your finger draws), then it might look something like:

- (void)touchesBegan:(NSSet *)touches withEvent:(UIEvent *)event
{
    UITouch *mytouch = [[touches allObjects] objectAtIndex:0];
    CGPoint location = [mytouch locationInView:self.view];

    myPath = [UIBezierPath bezierPath];
    [myPath moveToPoint:location];

    shapeLayer = [[CAShapeLayer alloc] initWithLayer:self.view.layer];
    shapeLayer.lineWidth = 1.0;
    shapeLayer.strokeColor = [UIColor redColor].CGColor;
    shapeLayer.fillColor = [UIColor clearColor].CGColor;

    [self.view.layer addSublayer:shapeLayer];
}

-(void)touchesMoved:(NSSet *)touches withEvent:(UIEvent *)event
{
    UITouch *mytouch = [[touches allObjects] objectAtIndex:0];
    CGPoint location = [mytouch locationInView:self.view];

    [myPath addLineToPoint:location];
    shapeLayer.path = myPath.CGPath;
}