Extension for `AppCompatActivity` to setup fullscreen window mode with specific status and navigation bar

FullscreenWindowExtensions.kt

package com.app.ext

import android.graphics.Color
import android.os.Build
import android.support.v7.app.AppCompatActivity
import android.view.View

/***
 * 
 * Extension for `AppCompatActivity` to setup fullscreen window mode with specific status and 
 * navigation bar.
 *
 * Example usage:
 *
 * ```
 *    override fun onResume() {
 *       super.onResume()
 *       setupFullscreenWindow(TransparentStatusBarOnDarkBg, TransparentNavigationBarOnDarkBg)
 *    }
 * ```
 *
 * Note: Don't forget to add `android:fitsSystemWindows="true"` to root viewgroup in XML layout of the activity.
 *
 */


open class StatusBar(val color: Int, val darkBackground: Boolean)

object TransparentStatusBarOnDarkBg : StatusBar(Color.TRANSPARENT, true)
object TransparentStatusBarOnLightBg : StatusBar(Color.TRANSPARENT, false)


open class NavigationBar(val placeAboveWindow: Boolean, val color: Int, val darkBackground: Boolean)

object TransparentNavigationBarOnDarkBg : NavigationBar(true, Color.TRANSPARENT, true)
object TransparentNavigationBarOnLightBg : NavigationBar(true, Color.TRANSPARENT, false)

fun AppCompatActivity.setupFullscreenWindow(statusBar: StatusBar, navigationBar: NavigationBar) {
    window?.decorView?.let {
        it.systemUiVisibility = View.SYSTEM_UI_FLAG_LAYOUT_FULLSCREEN or View.SYSTEM_UI_FLAG_LAYOUT_STABLE // Setup fullscreen window
        setupStatusBar(statusBar)
        setupNavigationBar(navigationBar)
    }
}

fun AppCompatActivity.setupStatusBar(statusBar: StatusBar) {
    window?.decorView?.let {
        if (Build.VERSION.SDK_INT >= Build.VERSION_CODES.LOLLIPOP) {
            // Setup background color (or black below Marshmallow when background color is not dark enough - because light status bar is supported on Marshmallow and above)
            if (Build.VERSION.SDK_INT < Build.VERSION_CODES.M && !statusBar.darkBackground) { // On Lollipop show black status bar when the background is light
                window?.statusBarColor = Color.BLACK
            } else {
                window?.statusBarColor = statusBar.color
            }

            // Setup dark icons color on light background (only Marshmallow and above)
            if (Build.VERSION.SDK_INT >= Build.VERSION_CODES.M && !statusBar.darkBackground) {
                it.systemUiVisibility = it.systemUiVisibility or View.SYSTEM_UI_FLAG_LIGHT_STATUS_BAR
            }
        }
    }
}

fun AppCompatActivity.setupNavigationBar(navigationBar: NavigationBar) {
    window?.decorView?.let {
        // Setup navigation bar - placement
        if (navigationBar.placeAboveWindow) {
            it.systemUiVisibility = it.systemUiVisibility or View.SYSTEM_UI_FLAG_LAYOUT_HIDE_NAVIGATION
        }

        // Setup navigation bar - colors
        if (Build.VERSION.SDK_INT >= Build.VERSION_CODES.LOLLIPOP) {
            // Setup background color (or black below Oreo MR1 when background color is not dark enough - because light navigation bar is supported on Oreo and above)
            if (Build.VERSION.SDK_INT < Build.VERSION_CODES.O_MR1 && !navigationBar.darkBackground) { // On Lollipop and Marshmallow show black navigation bar when the background is light
                window?.navigationBarColor = Color.BLACK
            } else {
                window?.navigationBarColor = navigationBar.color
            }

            // Setup dark icons color on light background (only Oreo MR1 and above)
            if (Build.VERSION.SDK_INT >= Build.VERSION_CODES.O_MR1 && !navigationBar.darkBackground) {
                it.systemUiVisibility = it.systemUiVisibility or View.SYSTEM_UI_FLAG_LIGHT_NAVIGATION_BAR
            }
        }
    }
}