如何删除带有角半径的CALayer周围的丑陋边框？

解决该问题的一种方法是创建的自定义子类，CALayer并重写该drawInContext方法以绘制带边框的圆。这是类的实现

@implementation DotLayer

- (instancetype)initWithFrame:(CGRect)frame
{
    self = [super init];
    if ( self )
    {
        self.frame = frame;
        self.backgroundColor = [UIColor clearColor].CGColor;
        self.borderColor = [UIColor whiteColor].CGColor;
        [self setNeedsDisplay];
    }
    return( self );
}

- (void)setBorderColor:(CGColorRef)borderColor
{
    [super setBorderColor:borderColor];
    [self setNeedsDisplay];
}

- (void)drawInContext:(CGContextRef)context
{
    CGRect rect = self.bounds;
    CGContextSetFillColorWithColor( context, self.borderColor );
    CGContextFillEllipseInRect( context, rect );

    rect = CGRectInset( self.bounds, 4, 4 );
    CGContextSetFillColorWithColor( context, [UIColor blackColor].CGColor );
    CGContextFillEllipseInRect( context, rect );
}

@end

这是添加点的代码

    DotLayer *layer = [[DotLayer alloc] initWithFrame:CGRectMake( xValue, yValue, 16, 16 )];
    [self.layer addSublayer:layer];

这是更改点的边框颜色的代码

    layer.borderColor = [UIColor greenColor].CGColor;