检测旋转CAShapeLayer上的接触

Question

我试图在自定义UIView中使用自定义CALayer实现UI元素。

基本上，用户用他/她的手指围绕一个圆移动滑块，所以我有一个用于交互的层，然后是表示滑块本身的CAShapeLayer类型的子层。我认为在圆周上移动滑块最简单的方法就是围绕它的z轴旋转CAShapeLayer。

尽管滑块在视觉上按预期旋转，但是当我对接收的触摸执行命中测试时，“可击中”区域仍驻留在滑块的预旋转位置。就好像CAShapeLayer的旋转的视觉效果与嵌入在图层内部的UIBezierPath解耦以形成图层的path属性，因为我正在使用该路径与CGPathContainsPoint()一起识别滑块上的触摸。

我是新来的核心图形一般，所以我想可能有一个属性，我没有在这里设置正确，但我努力弄清楚它是什么。

下面是代码：

TouchableLayer.m

@interface TouchableLayer() 
{ 
    CAShapeLayer *_slider; // The interactive slider that gets moved around the circle. 
} 

-(id) initWithPosition:(NSInteger) position // Designated initializer for this layer. 
{ 
    if (self = [super init]) 
    { 
     _slider = [CAShapeLayer layer]; 

     _slider.fillColor = [UIColor blackColor].CGColor; 

     [self addSublayer:_slider]; 
    } 

    return self; 
} 

-(void) setFrame:(CGRect)frame 
{ 
    [super setFrame:frame]; 

    _slider.frame = frame; 

    // This path is currently hardcoded to be in the right starting spot according to 
    // other UI elements, but the magic numbers will go away once I figure out this 
    // rotation issue. 
    _slider.path = [UIBezierPath bezierPathWithRect:CGRectMake(self.bounds.size.width-47, self.bounds.size.height/2-5, 30.0f, 10.0f)].CGPath; 

} 

// Checks if the given touch location was on the slider. Returns YES if it was and NO if it was not. 
-(BOOL) checkSliderTouchAtPoint: (CGPoint) point 
{ 
    if (CGPathContainsPoint(_slider.path , NULL, point, NO)) 
    { 
     return YES; 
    } 
    else 
    { 
     return NO; 
    } 
} 

// Purpose: Takes the given touch location, determines the angle (in radians) that it forms with respect the center of the screen, 
//    and returns that angle on the interval [0-2pi] radians. [0-2pi] radians follows a positive counterclockwise path. 
-(double) angleForTouchPoint:(CGPoint) point 
{ 
    // We use the positive counterclockwise coordinate system in the drawing code since that's what's used traditionally 
    // outside of Apple's APIs, so multiplying the result of 
    // atan2() by -1 converts the angle from a positive clockwise unit circle to a positive counterclockwise 
    // unit circle. 

    double angleInRadians = -1*atan2(point.y - (self.frame.size.height/2), point.x - self.frame.size.width/2); 

    if (angleInRadians < 0) // Convert angle to 0 - 2pi radians; we want non-negative angles. 
    { 
     angleInRadians += M_PI*2; 
    } 

    return angleInRadians; 
} 
// points get fed into this from the UIView. 
-(void) updateWithTouchAtPoint:(CGPoint) point 
{ 
    if ([self checkSliderTouchAtPoint:point]) 
    { 
     double touchAngle = [self angleForTouchPoint:point]; 
     _slider.transform = CATransform3DMakeRotation(-M_PI, 0.0, 0.0, 1.0); // Hardcoded angle rotation for now since I need to do some subtraction later in order to determine the amount to rotate based on touches. 
    } 
} 

我真的很感激任何帮助，您可以提供！

Answer 1

我通常会期望事件位置是以它们被传递到的UIView的形式表示的。由于_slider相对于其超级层（即UIView的支持层）有一个转换，因此您想要使用的任何几何值都需要转换为该参考帧。简而言之，您需要明确地将该点转换为_slider的参照系。尝试这样的：

-(BOOL) checkSliderTouchAtPoint: (CGPoint) point 
{ 
    CGPoint pointInSliderLayer = [_slider convertPoint: point fromLayer: self.layer]; 
    return CGPathContainsPoint(_slider.path , NULL, pointInSliderLayer, NO); 
}