ios - 如何自定义 UIInterpolatingMotionEffect 以根据设备的方向设置不同的阴影效果？

Question

我正在使用 UIInterpolatingMotionEffect 生成基于设备倾斜度的“阴影效果”。

我有一个带有一些文本的标签，并应用以下代码来获得效果:

// Set shadow properties
let layer = self.label.layer
layer.shadowColor = UIColor.blackColor().CGColor
layer.shadowRadius = 9
layer.shadowOpacity = 0.7
layer.shadowOffset = CGSizeMake(10, 10)

// Set vertical shadow effect
let verticalMotionEffect: UIInterpolatingMotionEffect = UIInterpolatingMotionEffect(keyPath: "layer.shadowOffset.height", type: .TiltAlongVerticalAxis)
verticalMotionEffect.minimumRelativeValue = 100
verticalMotionEffect.maximumRelativeValue = -100
    
// Set horizontal shadow effect
let horizontalMotionEffect: UIInterpolatingMotionEffect = UIInterpolatingMotionEffect(keyPath: "layer.shadowOffset.width", type: .TiltAlongHorizontalAxis)
horizontalMotionEffect.minimumRelativeValue = 100
horizontalMotionEffect.maximumRelativeValue = -100
    
// Create group to combine both
let group = UIMotionEffectGroup()
group.motionEffects = [horizontalMotionEffect, verticalMotionEffect]
    
// Add both effects to the label
self.label.addMotionEffect(group)

结果是这样的:

但我希望当设备静止或设备与眼睛平行时文本不可见。因此，必须旋转/倾斜设备才能理解所写的内容。

字体颜色为白色。在初始位置，阴影也应为白色或不透明度为 0，并根据设备倾斜度缓慢增加不透明度和半径。

我无法找到一种方法来捕获设备的倾斜值，然后我可以根据条件即兴创作以获得我想要的效果。我所有的网络搜索都将我引导至 CMMotionManager。有没有办法通过 UIInterpolatingMotionEffect 或 UIMotionEffect 来做到这一点？

提前致谢!

Answer 1

通过控制图层的阴影不透明度，我能够获得我想要的效果。我通过倾斜轴控制阴影不透明度，最小值和最大值分别为 -1.0 和 1.0，因为我希望不透明度最初为 0。这是代码:

let layer = self.layer
layer.shadowColor = UIColor.blackColor().CGColor
layer.shadowRadius = radius
//layer.shadowOpacity = opacity
layer.shadowOffset = CGSizeMake(offset, offset)

// Set vertical shadow effect
let verticalMotionEffect = UIInterpolatingMotionEffect(keyPath: "layer.shadowOffset.height", type: .TiltAlongVerticalAxis)
verticalMotionEffect.minimumRelativeValue = -parallaxIntensity
verticalMotionEffect.maximumRelativeValue = parallaxIntensity

// Set vertical shadow opacity effect
let verticalTransparencyEffect = UIInterpolatingMotionEffect(keyPath: "layer.shadowOpacity", type: .TiltAlongVerticalAxis)
verticalTransparencyEffect.minimumRelativeValue = -1.0
verticalTransparencyEffect.maximumRelativeValue = 1.0

// Set horizontal shadow effect
let horizontalMotionEffect = UIInterpolatingMotionEffect(keyPath: "layer.shadowOffset.width", type: .TiltAlongHorizontalAxis)
horizontalMotionEffect.minimumRelativeValue = -parallaxIntensity
horizontalMotionEffect.maximumRelativeValue = parallaxIntensity

// Set horizontal shadow opacity effect
let horizontalTransparencyEffect = UIInterpolatingMotionEffect(keyPath: "layer.shadowOpacity", type: .TiltAlongHorizontalAxis)
horizontalTransparencyEffect.minimumRelativeValue = -1.0
horizontalTransparencyEffect.maximumRelativeValue = 1.0

// Create group to combine all effects
let group = UIMotionEffectGroup()
group.motionEffects = [verticalMotionEffect, verticalTransparencyEffect, horizontalMotionEffect, horizontalTransparencyEffect]

// Add both effects to the label
self.addMotionEffect(group)

注意:需要禁用 layer.shadowOpacity 的手动设置才能工作。