Solved: Popup menu exits from Immersive Mode and shows navigation bar permanently

If you are using an activity which needs to hide navigation bar ( home, back buttons) and if you use popup menu in that activity, as soon as we click on popup menu, your activity looses the focus and android exits the immersive mode and shows the navigation bar.

Although by design this could be expected for Android, but for practical implementation this provides the challenge since we want our activity to be always hiding back/home buttons only till user wants to use it, but when using popup menu, the navigation bar sticks permanently after exit.

Solution : Reenter into Immersive mode by implementing onWindowFocusChanged()

As mentioned by Android at Immersive mode documents as,

Implement onWindowFocusChanged(). If you gain window focus, you may want to re-hide the system bars. If you lose window focus, for example due to a dialog or pop up menu showing above your app, you’ll probably want to cancel any pending “hide” operations you previously scheduled with Handler.postDelayed() or something similar.

Using Kotlin

override fun onWindowFocusChanged(hasFocus: Boolean) {
    super.onWindowFocusChanged(hasFocus)
    if (hasFocus) hideSystemUI()
}

private fun hideSystemUI() {
    // Enables regular immersive mode.
    // For "lean back" mode, remove SYSTEM_UI_FLAG_IMMERSIVE.
    // Or for "sticky immersive," replace it with SYSTEM_UI_FLAG_IMMERSIVE_STICKY
    window.decorView.systemUiVisibility = (View.SYSTEM_UI_FLAG_IMMERSIVE
            // Set the content to appear under the system bars so that the
            // content doesn't resize when the system bars hide and show.
            or View.SYSTEM_UI_FLAG_LAYOUT_STABLE
            or View.SYSTEM_UI_FLAG_LAYOUT_HIDE_NAVIGATION
            or View.SYSTEM_UI_FLAG_LAYOUT_FULLSCREEN
            // Hide the nav bar and status bar
            or View.SYSTEM_UI_FLAG_HIDE_NAVIGATION
            or View.SYSTEM_UI_FLAG_FULLSCREEN)
}

Using JAVA

@Override
public void onWindowFocusChanged(boolean hasFocus) {
    super.onWindowFocusChanged(hasFocus);
    if (hasFocus) {
        hideSystemUI();
    }
}

private void hideSystemUI() {
    // Enables regular immersive mode.
    // For "lean back" mode, remove SYSTEM_UI_FLAG_IMMERSIVE.
    // Or for "sticky immersive," replace it with SYSTEM_UI_FLAG_IMMERSIVE_STICKY
    View decorView = getWindow().getDecorView();
    decorView.setSystemUiVisibility(
            View.SYSTEM_UI_FLAG_IMMERSIVE
            // Set the content to appear under the system bars so that the
            // content doesn't resize when the system bars hide and show.
            | View.SYSTEM_UI_FLAG_LAYOUT_STABLE
            | View.SYSTEM_UI_FLAG_LAYOUT_HIDE_NAVIGATION
            | View.SYSTEM_UI_FLAG_LAYOUT_FULLSCREEN
            // Hide the nav bar and status bar
            | View.SYSTEM_UI_FLAG_HIDE_NAVIGATION
            | View.SYSTEM_UI_FLAG_FULLSCREEN);
}