在ios中以顺时针方向绘制圆弧

Question

如何从零开始以顺时针方向绘制圆弧环。我需要圆弧从0开始，并且圆弧终点可以变化。如图所示，图像中

Answer 1

我想要的是什么，开始从左侧的弧线。（ - 180）和我这样

-(void)drawRect:(CGRect)rect{ 

[super drawRect:rect]; 

CGRect customRect = rect; 
customRect.origin.x = 5; 
customRect.origin.y = 6; 
customRect.size.width = rect.size.width -10; 
customRect.size.height = rect.size.height - 12; 


radius = customRect.size.width/2 - ((customRect.size.width/2)*0.3); 


CGContextRef ctx = UIGraphicsGetCurrentContext(); 

CGContextSetRGBFillColor(ctx, 1.0, 0.0, 0.0, 1.0); 
CGContextFillEllipseInRect (ctx, customRect); 
CGContextStrokeEllipseInRect(ctx, customRect); 
CGContextFillPath(ctx); 
CGContextSetRGBStrokeColor(ctx, 0.0, 0.0, 1.0, 1.0); 
CGContextAddArc(ctx, self.frame.size.width/2 , self.frame.size.height/2, radius , -M_PI, ToRad(self.angle), 0); 

CGContextSetLineWidth(ctx, customRect.size.width/2 - (radius + 2)); 
CGContextDrawPath(ctx, kCGPathStroke); 
}