iOS点击文字按钮变转圈加载效果

// 画弧线- (void)drawHalfCircle {  loadingLayer = [self drawCircle];     // 这个是用于指定画笔的开始与结束点  loadingLayer.strokeStart = 0.0;  loadingLayer.strokeEnd = 0.75;} - (CAShapeLayer *)drawCircle {  CGRect frame = CGRectMake(0, 0, self.frame.size.height, self.frame.size.height);  CAShapeLayer *circleLayer = [CAShapeLayer layer];  // 指定frame，只是为了设置宽度和高度  circleLayer.frame = frame;  // 设置居中显示  circleLayer.position = CGPointMake(self.frame.size.height/2, self.frame.size.height/2);  // 设置填充颜色  circleLayer.fillColor = [UIColor clearColor].CGColor;  // 设置线宽  circleLayer.lineWidth = 1;  // 设置线的颜色  circleLayer.strokeColor = kSelfborderColor.CGColor;  // 使用UIBezierPath创建路径  UIBezierPath *circlePath = [UIBezierPath bezierPathWithOvalInRect:frame];  // 设置CAShapeLayer与UIBezierPath关联  circleLayer.path = circlePath.CGPath;  // 将CAShaperLayer放到某个层上显示  [self.layer addSublayer:circleLayer];  return circleLayer;}