Transparent background UIView drawRect circle

Question

I am drawing a circle with a white stroke and a color specified by a property using this code:

- (void)drawRect:(CGRect)rect {

    CGContextRef contextRef = UIGraphicsGetCurrentContext();

    CGContextClearRect(contextRef, rect);

    // Set the border width
    CGContextSetLineWidth(contextRef, 1.5);

    // Set the circle fill color to GREEN
    CGFloat red, green, blue, alpha;
    BOOL didConvert = [_routeColor getRed:&red green:&green blue:&blue alpha:&alpha];

    CGContextSetRGBFillColor(contextRef, red, green, blue, 1.0);

    // Set the cicle border color to BLUE
    CGContextSetRGBStrokeColor(contextRef, 255.0, 255.0, 255.0, 1.0);

    // Fill the circle with the fill color
    CGContextFillEllipseInRect(contextRef, rect);

    // Draw the circle border
    CGContextStrokeEllipseInRect(contextRef, rect);
}

The image I get back looks like this:

How can I remove the black?

Answer 1

Set the backgroundColor of the view to [UIColor clearColor].

Note that setting the background color only needs to be done once, when the view is created.

Answer 2

I needed this. When I set this, worked.

self.opaque = NO;

Answer 3

This worked for me on Swift 3:

self.isOpaque = false
self.backgroundColor = UIColor.clear

Answer 4

You need to set background color to clearColor in init.

Here is the example

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

    if(self)
    {
        self.backgroundColor = [UIColor clearColor];
    }

    return self;
}

- (void)drawRect:(CGRect)rect {

    CGContextRef contextRef = UIGraphicsGetCurrentContext();

    CGContextClearRect(contextRef, rect);

    // Set the border width
    CGContextSetLineWidth(contextRef, 1.5);

    // Set the circle fill color to GREEN
    CGFloat red, green, blue, alpha;
    BOOL didConvert = [_routeColor getRed:&red green:&green blue:&blue alpha:&alpha];

    CGContextSetRGBFillColor(contextRef, red, green, blue, 1.0);

    // Set the cicle border color to BLUE
    CGContextSetRGBStrokeColor(contextRef, 255.0, 255.0, 255.0, 1.0);

    // Fill the circle with the fill color
    CGContextFillEllipseInRect(contextRef, rect);

    // Draw the circle border
    CGContextStrokeEllipseInRect(contextRef, rect);
}