Parallax effect with UIMotionEffect not working

user_10032380 0
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My parallax effect for UIView is not working at all. I need something like a moving background image on iPhone tilt (pseudo-3D).

let horizontalMotionEffect = UIInterpolatingMotionEffect(keyPath: "center.x", type: .TiltAlongHorizontalAxis)
horizontalMotionEffect.minimumRelativeValue = -50
horizontalMotionEffect.maximumRelativeValue = 50

let verticalMotionEffect = UIInterpolatingMotionEffect(keyPath: "center.y", type: .TiltAlongVerticalAxis)
verticalMotionEffect.minimumRelativeValue = -50
verticalMotionEffect.maximumRelativeValue = 50

let motionEffectGroup = UIMotionEffectGroup()
motionEffectGroup.motionEffects = [horizontalMotionEffect, verticalMotionEffect]

imageView.addMotionEffect(motionEffectGroup)

I've tried to use this code. I've read https://www.hackingwithswift.com/example-code/uikit/how-to-create-a-parallax-effect-in-uikit but my imageView remains static.

I'm using Xcode 11, iOS 13.

uimotioneffect parallax swift uikit ios
1 Answers

In the code that you have shared, one thing that I noticed is that you are using capital T in the enums .TiltAlongHorizontalAxis and .TiltAlongVerticalAxis, which don't compile (at least on Xcode 11.4.1) -> those need to be changed to lowercase T.

Apple's documentation for those enums is here.

Other than that, I don't see any problems with the code that you shared. In fact I created a sample project with a simple imageView in the view to which I added constraints so that it fills up the entire space of its superview.

I then added the motion effects code that you shared, and ran it on an actual device (iPad Pro). It worked perfectly.

Could you check a few things that might be a source of the problem:

  • Double check that Settings > Accessibility > Motion > Reduce Motion is not turned on. Because if it is turned on, then UIInterpolatingMotionEffect won't work.
  • Test that the accelerometer of the device that you are testing on actually works. Or better still, use another device to test it. (This won't work on the simulator).
  • If you are editing the frame of the imageView in code anywhere (or especially in viewWillLayout / viewDidLayout), you shouldn't be doing that.

In any case, if none of these things help you to fix your problem, can you create a simple sample project which demonstrates the bug and post it on Github? I can try to help if I can actually reproduce the problem.

user_23721890
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