旋转CALayers

Question

我已经完成了下面的教程来创建一个UIKit旋转轮控制。 http://www.raywenderlich.com/9864/how-to-create-a-rotating-wheel-control-with-uikit

部分中“摆出轮”的教程，车轮被绘制顺时针开始圆的左侧部位（见的红色标签的截图）。所以它从左边的网站开始。

但是，我想从0的圆圈的正确位置开始 - 现在屏幕截图上的位置是4。不幸的是，我不知道如何才能做到这一点。当然，数字或图片的旋转应该与现在完全相反。所以现在4旋转180度，这应该是正常的。

有人可以帮我吗？会很好。

问候

当前drawWheel功能：

// 3 - Create the sectors 
for (int i = 0; i < _numberOfSections; i++) { 
    // 4 - Create image view 
    UIImageView *im = [[UIImageView alloc] initWithImage:[UIImage imageNamed:@"segment.png"]]; 
    im.layer.anchorPoint = CGPointMake(1.0f, 0.5f); 
    im.layer.position = CGPointMake(_container.bounds.size.width/2.0-_container.frame.origin.x, 
            _container.bounds.size.height/2.0-_container.frame.origin.y); 
    im.transform = CGAffineTransformMakeRotation((angleSize * i) + M_PI); 
    im.alpha = minAlphavalue; 
    im.tag = i; 
    if (i == 0) { 
     im.alpha = maxAlphavalue; 
    } 
    // 5 - Set sector image 
    UIImageView *sectorImage = [[UIImageView alloc] initWithFrame:CGRectMake(12, 100, 40, 40)]; 
    sectorImage.image = [UIImage imageNamed:[NSString stringWithFormat:@"icon%i.png", i]]; 
    [im addSubview:sectorImage]; 
    // 6 - Add image view to container 
    [_container addSubview:im]; 
} 

Answer 1

未经检验的，但你就不能添加M_PI？

- (void) drawWheel { 
    container = [[UIView alloc] initWithFrame:self.frame]; 
    CGFloat angleSize = 2*M_PI/numberOfSections; 
    for (int i = 0; i < numberOfSections; i++) { 
     UILabel *im = [[UILabel alloc] initWithFrame:CGRectMake(0, 0, 100, 40)]; 
     im.backgroundColor = [UIColor redColor]; 
     im.text = [NSString stringWithFormat:@"%i", i]; 
     im.layer.anchorPoint = CGPointMake(1.0f, 0.5f); 
     im.layer.position = CGPointMake(container.bounds.size.width/2.0, 
             container.bounds.size.height/2.0); 
     // ===== Add M_PI Here! ===== 
     im.transform = CGAffineTransformMakeRotation((angleSize * i) + M_PI); 
     // ========================== 
     im.tag = i; 
     [container addSubview:im]; 
    } 
    container.userInteractionEnabled = NO; 
    [self addSubview:container]; 
}