UIBezierPath to draw straight lines - objective-c

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;
}

Answer 2

I would not use UIBezierPath since it is intended more for drawing curved paths.
The most efficient way to accomplish this would be to use core graphics draw commands within drawRect while using an array to store the points you want to draw; this array is appended to in your touch methods.
- (void)drawRect:(CGRect)rect {
CGContextRef c = UIGraphicsGetCurrentContext();
CGFloat black[4] = {0, 0,
0, 1};
CGContextSetStrokeColor(c, black);
CGContextBeginPath(c);
CGContextMoveToPoint(c, 100, 100);
CGContextAddLineToPoint(c, 100, 200); //call this in a loop that goes through the point array
CGContextStrokePath(c);
}
There is much more information here: Quartz 2D Programming Guide
Hope this helps!