Draw a line between two points - How to pass UIView - uiview

Question

I am trying to draw a simple line connecting two points. I think i got the right code for that in my drawLine method. No lines appear at all and I am pretty sure it has to do with the View I am calling with and the one I want to draw on. The following code is where I build my next View in code (data coming from a web service). The View gets created just fine and all buttons and objects appear.
I am trying to add lines to the View I'm creating (Next) dynamically and not sure how to get that done. From the Errors I get (invalid context 0x0) it seems I am doing something out of order. Trying to display on a view that is not there. how than can I get this done? Any advice would be appreciated.
I realize that passing on the View might not be the right answer. I am in the midst of trial and error here.
To clarify: I am calling drawLine here:
[nextView.view addSubview:next];
Thanks,
Shai
-(void) drawView
{
CGRect rec;
CGFloat width = [UIScreen mainScreen].bounds.size.width;
CGFloat height = [UIScreen mainScreen].bounds.size.height;
UIView *next = [[UIView alloc]initWithFrame:CGRectMake(0, 0, height, width)];
next.backgroundColor = [UIColor whiteColor];
next.userInteractionEnabled = YES;
next.multipleTouchEnabled = YES;
nextView = [UIViewController alloc];
[nextView setTitle: as_objectDesc];
for (object in viewObjects)
{ // ratio based on Ipad 2 screen size conversion from the Datawindow size - alter to support other device
CGFloat objWidth = object.Width/3.83;
CGFloat objHeight = object.Height/2.78;
CGFloat objXPoint = object.positionX/3.83;
CGFloat objYPoint = object.positionY/2.78;
if ([object.Shape isEqualToString:#"text"])
{
rec = CGRectMake(objXPoint, objYPoint, objWidth, objHeight);
UILabel *myLabel = [[UILabel alloc] initWithFrame:rec];
myLabel.backgroundColor = [UIColor clearColor];
myLabel.text = object.objectTag;
myLabel.lineBreakMode = NSLineBreakByWordWrapping;
if ([object.description isEqualToString:#"Header"])
{
myLabel.font = [UIFont systemFontOfSize:20];
}
else
{
myLabel.font = [UIFont systemFontOfSize:10];
}
[next addSubview:myLabel];
}
else if ([object.Shape isEqualToString:#"line"])
{
**[self drawLine:nextView.view];**
}
else
{
UIButton *myButton = [UIButton buttonWithType:UIButtonTypeCustom];
if ([object.Shape isEqualToString:#"ellipse"])
{
UIImage * buttonImage;
if ([object.Color isEqualToString:#"255"])
{
buttonImage = [UIImage imageNamed:#"redBackground.png"];
}
else if ([object.Color isEqualToString:#"65535"])
{
buttonImage = [UIImage imageNamed:#"yellowBackground.png"];
}
else if ([object.Color isEqualToString:#"GRAY"])
{
buttonImage = [UIImage imageNamed:#"graybground.PNG"];
}
else if ([object.Color isEqualToString:#"BLACK"])
{
buttonImage = [UIImage imageNamed:#"BlackBackground.png"];
}
[myButton setBackgroundImage:buttonImage forState: UIControlStateNormal];
objWidth = objHeight;
rec = CGRectMake(objXPoint, objYPoint, objWidth, objHeight);
myButton.frame = rec;
myButton.clipsToBounds = YES;
myButton.layer.cornerRadius = objWidth/2;
}
else
{
rec = CGRectMake(objXPoint, objYPoint, objWidth, objHeight);
if ([object.Color isEqualToString:#"255"])
myButton.backgroundColor = [UIColor redColor];
else if ([object.Color isEqualToString:#"65535"])
myButton.backgroundColor = [UIColor yellowColor];
else if ([object.Color isEqualToString:#"GRAY"])
myButton.backgroundColor = [UIColor grayColor];
else if ([object.Color isEqualToString:#"BLACK"])
myButton.backgroundColor = [UIColor blackColor];
}
[[myButton layer] setBorderWidth:1.0f];
[[myButton layer] setBorderColor:[UIColor blackColor].CGColor];
myButton.enabled = YES;
myButton.accessibilityHint = object.objectTag;
myButton.titleLabel.lineBreakMode = NSLineBreakByWordWrapping;
myButton.titleLabel.textAlignment = NSTextAlignmentCenter;
myButton.titleLabel.font = [UIFont systemFontOfSize:13];
[myButton setTitleColor:[UIColor blackColor] forState:UIControlStateNormal];
[myButton addTarget:self action:#selector(btnClick:) forControlEvents:UIControlEventTouchUpInside];
myButton.frame = rec;
[myButton setTitle:object.description forState:UIControlStateNormal];
// Check if an Empty Rectangle
NSRange test =[myButton.accessibilityHint rangeOfString:#"r_"];
if (test.location == 0)
{
[next sendSubviewToBack:myButton];
[myButton setEnabled:NO];
}
[next addSubview:myButton];
}
UIPinchGestureRecognizer *twoFingerPinch = [[UIPinchGestureRecognizer alloc]
initWithTarget:self
action:#selector(twoFingerPinch:)]
;
[[nextView view] addGestureRecognizer:twoFingerPinch];
[next addSubview:activityIndicator];
[next bringSubviewToFront:activityIndicator];
}
[nextView.view addSubview:next];
[self dismissViewControllerAnimated:NO completion:nil];
[self.navigationController pushViewController:nextView animated:NO];
}
- (void)drawLine:(UIView *) view
{
CGFloat x1 = object.positionX;
CGFloat y1 = object.positionY;
CGFloat x2 = object.positionX2;
CGFloat y2 = object.positionY2;
CGContextRef context = UIGraphicsGetCurrentContext();
if ([object.Color isEqualToString:#"255"])
CGContextSetStrokeColorWithColor(context, [UIColor redColor].CGColor);
else if ([object.Color isEqualToString:#"65535"])
CGContextSetStrokeColorWithColor(context, [UIColor yellowColor].CGColor);
else if ([object.Color isEqualToString:#"GRAY"])
CGContextSetStrokeColorWithColor(context, [UIColor grayColor].CGColor);
else if ([object.Color isEqualToString:#"BLACK"])
CGContextSetStrokeColorWithColor(context, [UIColor blackColor].CGColor);
CGContextSetLineWidth(context, 3.0);
CGContextBeginPath(context);
CGContextMoveToPoint(context, x1, y1);
CGContextAddLineToPoint(context, x2, y2);
CGContextStrokePath(context);
}

Answer 1

I end up figuring this up days a go and thought I would share here. I might have added to much code in my question which did not help to simplify it to others (no comments).
What this came down to is when trying to Draw a line you need to override the DrawRect Method of the UIView subclass and not the UIViewController as I did. There is no Error thrown if you call DrawRect from your UIViewController but it doesn't do anything. I missed that small detail.
What added to the complexity of finding this out ans solving this was that I was creating all of it Programmatically and initially didn't subclass UIView at all. I ended up adding all the Points in an NSMutablearray and redrawing the lines in the following class after the newly View got created:
#import "draw.h"
#implementation draw
#synthesize lines;
- (id)initWithFrame:(CGRect)frame
{
self = [super initWithFrame:frame];
if (self)
{
// Initialization code
}
return self;
}
-(void)drawRect:(CGRect)rect
{
CGContextRef context = UIGraphicsGetCurrentContext();
for (line *myLine in lines)
{
if ([myLine.color isEqualToString:#"255"])
CGContextSetStrokeColorWithColor(context, [UIColor redColor].CGColor);
else if ([myLine.color isEqualToString:#"65535"])
CGContextSetStrokeColorWithColor(context, [UIColor yellowColor].CGColor);
else if ([myLine.color isEqualToString:#"GRAY"])
CGContextSetStrokeColorWithColor(context, [UIColor grayColor].CGColor);
else if ([myLine.color isEqualToString:#"BLACK"])
CGContextSetStrokeColorWithColor(context, [UIColor blackColor].CGColor);
int setNew = myLine.Width/4;
CGContextSetLineWidth(context, (CGFloat)setNew);
CGContextBeginPath(context);
CGContextMoveToPoint(context, myLine.x1, myLine.y1);
CGContextAddLineToPoint(context, myLine.x2, myLine.y2);
CGContextStrokePath(context);
}
}
#end