Question

Whats wrong with this code?

-(void) drawRect:(CGRect) rect {
        CGContextRef c = UIGraphicsGetCurrentContext();
        if (c != nil)  {
            CGContextSetFillColorWithColor(c, self.cornerColor.CGColor);
            [self drawRoundedCornersInRect:self.bounds inContext:c];
            CGContextFillPath(c);
        }
    }

    -(void) drawCornerInContext:(CGContextRef)c cornerX:(int) x cornerY:(int) y
            arcEndX:(int) endX arcEndY:(int) endY {
        CGContextMoveToPoint(c, x, endY);
        CGContextAddArcToPoint(c, x, y, endX, y, radius);
        CGContextAddLineToPoint(c, x, y);
        CGContextAddLineToPoint(c, x, endY);
    }

    -(void) drawRoundedCornersInRect:(CGRect) rect inContext:(CGContextRef) c  {
     int x_left = rect.origin.x;
     int x_left_center = rect.origin.x + radius;
     int x_right_center = rect.origin.x + rect.size.width - radius;
     int x_right = rect.origin.x + rect.size.width;
     int y_top = rect.origin.y;
     int y_top_center = rect.origin.y + radius;
     int y_bottom_center = rect.origin.y + rect.size.height - radius;
     int y_bottom = rect.origin.y + rect.size.height;

        if (roundUpperLeft) {
            [self drawCornerInContext:c cornerX: x_left cornerY: y_top
                  arcEndX: x_left_center arcEndY: y_top_center];
        }

        if (roundUpperRight) {
            [self drawCornerInContext:c cornerX: x_right cornerY: y_top
                  arcEndX: x_right_center arcEndY: y_top_center];
        }

        if (roundLowerRight) {
            [self drawCornerInContext:c cornerX: x_right cornerY: y_bottom
                  arcEndX: x_right_center arcEndY: y_bottom_center];
        }

        if (roundLowerLeft) {
            [self drawCornerInContext:c cornerX: x_left cornerY: y_bottom
                  arcEndX: x_left_center arcEndY: y_bottom_center];
        }
    }

No errors, No warnings … but the round corners don’t work at all. I found this code here.

Answer 1

You need to begin a path, and close it when you’re done. Your 2nd call to CGContextAddLineToPoint messes things up I think. Here’s a snippet that works. Study it and enhance it to support your multiple cases (it seems that you want to be able to round only some corners, and not necessarily all of them…)

void addRoundedRect(CGContextRef ctx, CGRect rect, float cornerRadius) {
    if (cornerRadius <= 2.0) {
        CGContextAddRect(ctx, rect);
    } else {
        float x_left = rect.origin.x;
        float x_left_center = x_left + cornerRadius;
        float x_right_center = x_left + rect.size.width - cornerRadius;
        float x_right = x_left + rect.size.width;
        float y_top = rect.origin.y;
        float y_top_center = y_top + cornerRadius;
        float y_bottom_center = y_top + rect.size.height - cornerRadius;
        float y_bottom = y_top + rect.size.height;
        /* Begin path */
        CGContextBeginPath(ctx);
        CGContextMoveToPoint(ctx, x_left, y_top_center);
        /* First corner */
        CGContextAddArcToPoint(ctx, x_left, y_top, x_left_center, y_top, cornerRadius);
        CGContextAddLineToPoint(ctx, x_right_center, y_top);
        /* Second corner */
        CGContextAddArcToPoint(ctx, x_right, y_top, x_right, y_top_center, cornerRadius);
        CGContextAddLineToPoint(ctx, x_right, y_bottom_center);
        /* Third corner */
        CGContextAddArcToPoint(ctx, x_right, y_bottom, x_right_center, y_bottom, cornerRadius);
        CGContextAddLineToPoint(ctx, x_left_center, y_bottom);
        /* Fourth corner */
        CGContextAddArcToPoint(ctx, x_left, y_bottom, x_left, y_bottom_center, cornerRadius);
        CGContextAddLineToPoint(ctx, x_left, y_top_center);
        /* Done */
        CGContextClosePath(ctx);
    }
}