畫圈

 CAShapeLayer *circle = [CAShapeLayer layer];
    
    [circle setPath:[[UIBezierPath bezierPathWithOvalInRect:CGRectMake(100, 100, 150, 150)] CGPath]];
    
    [circle setStrokeColor:[[UIColor blueColor] CGColor]];

    [circle setFillColor:[[UIColor clearColor] CGColor]];
    
    [[self.view layer] addSublayer:circle];

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