[iOS] UIBezierPath画圆弧 addArcWithCenter

UIBezierPath通过

- (void)addArcWithCenter:(CGPoint)center radius:(CGFloat)radius startAngle:(CGFloat)startAngle endAngle:(CGFloat)endAngle clockwise:(BOOL)clockwise

可以画出一段弧线。

看下各个参数的意义：

center：圆心的坐标

radius：半径

startAngle：起始的弧度

endAngle：圆弧结束的弧度

clockwise：YES为顺时针，No为逆时针

方法里面主要是理解startAngle与endAngle，刚开始我搞不清楚一段圆弧从哪算起始和终止，比如弧度为0的话，是从上下左右哪个点开始算

CAShapeLayer *layer = [[CAShapeLayer alloc] init];
    layer.name = @"Radius";
    CGFloat lineWidth =  10;
    UIBezierPath *path = [UIBezierPath bezierPath];
    path.lineWidth = lineWidth;
    path.lineCapStyle = kCGLineCapButt;
    CGPoint center = CGPointMake(self.bounds.size.width/2, self.bounds.size.height/2);
    CGFloat radius = (self.bounds.size.width - lineWidth)/2;
    
    CGFloat startAngle = -((float)M_PI)/7; //
    CGFloat endAngle = ((float)M_PI)-startAngle ;
    
    [[UIColor whiteColor] set];
    
    [path addArcWithCenter:center radius:radius startAngle:startAngle endAngle:endAngle clockwise:YES];
    
    [path stroke];
    
    [path closePath];