BottomNavigationBar behaviour

[JoaquimLey]

Makes sense to add a scrolling behavior to the BottomNavigationBar for better visibility

Here's the link to the article: https://android.jlelse.eu/scroll-your-bottom-navigation-view-away-with-10-lines-of-code-346f1ed40e9e?__s=ep727fgnkqv7dsftb1ut

Tasks ⚙

• Copy The code into project

• Set the behavior to the HomeActivity's BottomNavigationBar

The code

class BottomNavigationBehavior<V : View>(context: Context, attrs: AttributeSet) : CoordinatorLayout.Behavior<V>(context, attrs) {

	override fun onStartNestedScroll(coordinatorLayout: CoordinatorLayout, child: V, directTargetChild: View, target: View, axes: Int, type: Int): Boolean {
		return axes == ViewCompat.SCROLL_AXIS_VERTICAL
	}

	override fun onNestedPreScroll(coordinatorLayout: CoordinatorLayout, child: V, target: View, dx: Int, dy: Int, consumed: IntArray, type: Int) {
		super.onNestedPreScroll(coordinatorLayout, child, target, dx, dy, consumed, type)
		child.translationY = max(0f, min(child.height.toFloat(), child.translationY + dy))
	}

	override fun layoutDependsOn(parent: CoordinatorLayout?, child: V, dependency: View?): Boolean {
		if (dependency is Snackbar.SnackbarLayout) {
			updateSnackbar(child, dependency)
		}
		return super.layoutDependsOn(parent, child, dependency)
	}

	private fun updateSnackbar(child: View, snackbarLayout: Snackbar.SnackbarLayout) {
		if (snackbarLayout.layoutParams is CoordinatorLayout.LayoutParams) {
			val params = snackbarLayout.layoutParams as CoordinatorLayout.LayoutParams

			params.anchorId = child.id
			params.anchorGravity = Gravity.TOP
			params.gravity = Gravity.TOP
			snackbarLayout.layoutParams = params
		}
	}
}

And on the BottomNavigationView XML add this attribute

app:layout_behavior="com.joaquimley.transporteta.<_SOME_PACKAGE_>.BottomNavigationBehavior"

[JoaquimLey]

This might not be needed with the release of 28-alpha