ScrollingViewAboveBottomNavigationBehavior

gistfile1.txt

set this on your scrolling view for which you wish to have the behavior applied:

app:layout_behavior="com.myapp.mypackage.ScrollingViewAboveBottomNavigationBehavior"

ScrollingViewAboveBottomNavigationBehavior.kt

import android.content.Context
import android.util.AttributeSet
import android.view.View
import androidx.coordinatorlayout.widget.CoordinatorLayout
import com.google.android.material.appbar.AppBarLayout
import com.google.android.material.bottomnavigation.BottomNavigationView

/**
 * Extension of standard [AppBarLayout.ScrollingViewBehavior] which
 * ensures the scrollview bottom aligns with the top of the view below it,
 * such as a BottomNavigationView
 */
class ScrollingViewAboveBottomNavigationBehavior @JvmOverloads constructor(context: Context, attrs: AttributeSet? = null) :
    AppBarLayout.ScrollingViewBehavior(context, attrs) {

    private var marginBottom = 0

    override fun layoutDependsOn(parent: CoordinatorLayout, child: View, dependency: View): Boolean =
        super.layoutDependsOn(parent, child, dependency) || dependency is BottomNavigationView

    override fun onDependentViewChanged(parent: CoordinatorLayout, child: View, dependency: View): Boolean {
        return if (dependency is BottomNavigationView && dependency.getMeasuredHeight() != marginBottom) {
            marginBottom = dependency.getMeasuredHeight()
            child.layoutParams = (child.layoutParams as CoordinatorLayout.LayoutParams).apply {
                bottomMargin = marginBottom
            }
            true
        } else super.onDependentViewChanged(parent, child, dependency)
    }

}