Question

I have a class called MNTRectangle which is a subclass of UIImage. I have overridden the drawRect method of this class to draw a border on the image (using its frame). I have it so when the user starts a panning/dragging gesture on a class called DocumentView (subclass of UIView) it adds an instance of MNTRectangle as a subview to the instance of DocumentView. As the user continues to drag the MNTRectangle is resized. The problem is that the MNTRectangle is appearing as solid black in the end, I have tried clearing the graphics context as well as saving the context before drawing the border and restoring the context after drawing the border. No matter what I seem to try I cannot get the MNTRectangle to clear and just show the border on resize.

Here is the code for my MNTRectangle class:

@implementation MNTRectangle

- (id)init
{
    self = [super init];

    if (self)
    {
        [self setup];
    }

    return self;
}

- (id)initWithCoder:(NSCoder *)aDecoder
{
    self = [super initWithCoder:aDecoder];

    if (self)
    {
        [self setup];
    }

    return self;
}

- (id)initWithFrame:(CGRect)frame
{
    self = [super initWithFrame:frame];

    if (self)
    {
        [self setup];
    }

    return self;
}

- (void)setup
{
    [self setBackgroundColor:[UIColor clearColor]];
}

- (void)drawRect:(CGRect)rect
{
    // Get graphics context
    CGContextRef context = UIGraphicsGetCurrentContext();

//    CGContextSaveGState(context);

//    CGContextClearRect(context, rect);

    // Draw border
    CGContextSetLineWidth(context, 4.0);
    [[UIColor blackColor] setStroke];
    CGContextStrokeRect(context, rect);

//    CGContextRestoreGState(context);
}

Here is the code in DocumentView for the panning/dragging handling on the UIView:

-(id)initWithFrame:(CGRect)frame
{
    self = [super initWithFrame:frame];

    if (self)
    {
         _panGesture = [[UIPanGestureRecognizer alloc] initWithTarget:self action:@selector(handlePan:)];
    }

    return self;
}

- (void)handlePan:(UIPanGestureRecognizer *)sender
{
    if ([sender state] == UIGestureRecognizerStateBegan)
    {
        _startPanPoint = [sender locationInView:self];

        MNTRectangle *rectangle = [[MNTRectangle alloc] initWithFrame:CGRectMake(_startPanPoint.x, _startPanPoint.y, 1, 1)];
        [_objects addObject:rectangle];
        _currentPanObject = rectangle;
        [self addSubview:rectangle];
    }
    else if ([sender state] == UIGestureRecognizerStateChanged)
    {
        CGPoint endPanPoint = [sender locationInView:self];

        float height = fabsf(endPanPoint.y - _startPanPoint.y);
        float width = fabsf(endPanPoint.x - _startPanPoint.x);
        float x = MIN(_startPanPoint.x, endPanPoint.x);
        float y = MIN(_startPanPoint.y, endPanPoint.y);

        MNTRectangle *rectangle = (MNTRectangle *)_currentPanObject;
        [rectangle setFrame:CGRectMake(x, y, width, height)];
    }
    else if ([sender state] == UIGestureRecognizerStateEnded)
    {
        CGPoint endPanPoint = [sender locationInView:self];

        float height = fabsf(endPanPoint.y - _startPanPoint.y);
        float width = fabsf(endPanPoint.x - _startPanPoint.x);
        float x = MIN(_startPanPoint.x, endPanPoint.x);
        float y = MIN(_startPanPoint.y, endPanPoint.y);

        MNTRectangle *rectangle = (MNTRectangle *)_currentPanObject;
        [rectangle setFrame:CGRectMake(x, y, width, height)];
    }
}

Any help with this would be greatly appreciated.

Answer 1

I finally figured it out. In my handlePan: method after I set the frame of the rectangle I was missing [rectangle setNeedsDisplay];.

Now my DocumentView code looks like this:

-(id)initWithFrame:(CGRect)frame
{
   self = [super initWithFrame:frame];

    if (self)
    {
         _panGesture = [[UIPanGestureRecognizer alloc] initWithTarget:self action:@selector(handlePan:)];
    }

    return self;
}

- (void)handlePan:(UIPanGestureRecognizer *)sender
{
   if ([sender state] == UIGestureRecognizerStateBegan)
   {
        _startPanPoint = [sender locationInView:self];

        MNTRectangle *rectangle = [[MNTRectangle alloc] initWithFrame:CGRectMake(_startPanPoint.x, _startPanPoint.y, 1, 1)];
        [_objects addObject:rectangle];
        _currentPanObject = rectangle;
        [self addSubview:rectangle];
    }
    else if ([sender state] == UIGestureRecognizerStateChanged)
    {
        CGPoint endPanPoint = [sender locationInView:self];

        float height = fabsf(endPanPoint.y - _startPanPoint.y);
        float width = fabsf(endPanPoint.x - _startPanPoint.x);
        float x = MIN(_startPanPoint.x, endPanPoint.x);
        float y = MIN(_startPanPoint.y, endPanPoint.y);

        MNTRectangle *rectangle = (MNTRectangle *)_currentPanObject;
        [rectangle setFrame:CGRectMake(x, y, width, height)];
        [rectangle setNeedsDisplay];
    }
    else if ([sender state] == UIGestureRecognizerStateEnded)
    {
        CGPoint endPanPoint = [sender locationInView:self];

        float height = fabsf(endPanPoint.y - _startPanPoint.y);
        float width = fabsf(endPanPoint.x - _startPanPoint.x);
        float x = MIN(_startPanPoint.x, endPanPoint.x);
        float y = MIN(_startPanPoint.y, endPanPoint.y);

        MNTRectangle *rectangle = (MNTRectangle *)_currentPanObject;
        [rectangle setFrame:CGRectMake(x, y, width, height)];
        [rectangle setNeedsDisplay];
    }
}