检测旋转CAShapeLayer上的接触

Question

我试图在自定义CALayer中使用自定义UIView实现UI元素。

基本上，用户用他/她的手指在一个圆圈上移动一个滑块，所以我有一个交互层，然后是一个CAShapeLayer类型的子层，它表示滑块本身。我想，移动滑块的最简单的方法就是旋转CAShapeLayer的z轴。

虽然滑块确实按预期在视觉上旋转，但当我对接收到的触点执行命中测试时，“可命中”区域仍然驻留在滑块的预旋转位置。这就好像CAShapeLayer旋转的视觉效果与嵌入在层中的UIBezierPath解耦，从而形成层的path属性，因为我使用该路径与CGPathContainsPoint()一起识别滑块上的触点。

总的来说，我对核心图形( Core Graphics )还不熟悉，所以我认为这里可能有一个我没有正确设置的属性，但我很难弄清楚它是什么。

以下是代码：

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.
    }
}

我真的很感激你能提供的任何帮助！

Answer 1

我通常认为，事件位置是用传递给的UIView来表示的。由于在_slider上有一个关于它的上层(即UIView的支持层)的转换，您想要使用的任何几何值都需要转换成那个参照系。简而言之，您需要显式地将这一点转换为_slider的参考框架。

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