Using isMotionEnabled on BottomNavigationController/UITabBarController causes delegate methods to not be called

[Andrew Chen]

It seems as though setting the delegate on a BottomNavigationController causes Motion to be disabled while enabling Motion causes delegate methods to not be called.

Material 2.13.5
Motion 1.3.4

BottomNavigationController.zip

[Daniel Jonathan]

I will take a look at your sample. Thank you for sharing this issue.

[Daniel Jonathan]

@OrkhanAlikhanov Let's confirm if this is still an issue. Thank you and apologies for taking a very long time to respond.

[Orkhan Alikhanov]

@DanielDahan I confirm that this issue is still there. I investigated it a bit. Here is my summary.

The issue

Setting isMotionEnabled = true changes the delegate but does not forward the delegation methods to previousTabBarDelegate.

class AppBottomNavigationController: BottomNavigationController {
  override func prepare() {
        super.prepare()
        delegate = self
        print(delegate === self) // true
        isMotionEnabled = true // changes `delegate`
        print(delegate === self) // false

        isMotionEnabled = false // sets `previousTabBarDelegate` back
        print(delegate === self) // true
    }
}

extension AppBottomNavigationController: UITabBarControllerDelegate {
    func tabBarController(_ tabBarController: UITabBarController, didSelect viewController: UIViewController) {
        print("hi") // never called if `isMotionEnabled == true`
    }
}

Possible solution

I think forwarding delegation methods to the tabBarController.previousTabBarDelegate will solve the problem but I am unsure about its side effects. Here is the file where it should be done.

Motion/Sources/Transition/MotionTransition+UITabBarControllerDelegate.swift

Lines 31 to 32 in b3595d0

 extension MotionTransition: UITabBarControllerDelegate { 
   public func tabBarController(_ tabBarController: UITabBarController, shouldSelect viewController: UIViewController) -> Bool { 

[Daniel Jonathan]

@OrkhanAlikhanov I believe this issue may be closed. Please take a look at Motion 1.4.2 to test if this is still an issue. Thank you!