Maintain Immersive mode when DialogFragment is Shown

I know this is old but I was struggling with this for a while as I had dialogFragments and a drop down in my navigationView that kept revealing the system UI needlessly. Here are the things I did that ended up working (the first two pieces I found a lot of places):

In my AndroidManifest.xml on the application

android:theme="@style/AppTheme.NoActionBar"

In my activity

View decorView = getWindow().getDecorView();
int uiOptions = View.SYSTEM_UI_FLAG_FULLSCREEN | View.SYSTEM_UI_FLAG_IMMERSIVE_STICKY | View.SYSTEM_UI_FLAG_HIDE_NAVIGATION;
decorView.setSystemUiVisibility(uiOptions);

And what ended up being the key for me is in my styles.xml

<resources>
    <!-- Base application theme. -->
    <style name="AppTheme" parent="Theme.AppCompat.Light.DarkActionBar">
        <!-- Customize your theme here. -->
        <item name="android:windowNoTitle">true</item>
        <item name="android:windowFullscreen">true</item>
    </style>
</resources>

1. Explanation for solution.

I have taken the following quotes from the android api docs.

Using Immersive Full-Screen Mode

When immersive full-screen mode is enabled, your activity continues to receive all touch events. The user can reveal the system bars with an inward swipe along the region where the system bars normally appear. This clears the SYSTEM_UI_FLAG_HIDE_NAVIGATION flag (and the SYSTEM_UI_FLAG_FULLSCREEN flag, if applied) so the system bars become visible. This also triggers your View.OnSystemUiVisibilityChangeListener, if set.

Firstly, you don't need an OnSystemUiVisibilityChangeListener when using sticky immersion.

However, if you'd like the system bars to automatically hide again after a few moments, you can instead use the SYSTEM_UI_FLAG_IMMERSIVE_STICKY flag. Note that the "sticky" version of the flag doesn't trigger any listeners, as system bars temporarily shown in this mode are in a transient state.

The recommendations for using sticky/non sticky immersion:

If you're building a truly immersive app, where you expect users to interact near the edges of the screen and you don't expect them to need frequent access to the system UI, use the IMMERSIVE_STICKY flag in conjunction with SYSTEM_UI_FLAG_FULLSCREEN and SYSTEM_UI_FLAG_HIDE_NAVIGATION. For example, this approach might be suitable for a game or a drawing app.

However, you mention users needing the keyboard, so I suggest this:
Use Non-Sticky Immersion

If you're building a book reader, news reader, or a magazine, use the IMMERSIVE flag in conjunction with SYSTEM_UI_FLAG_FULLSCREEN and SYSTEM_UI_FLAG_HIDE_NAVIGATION. Because users may want to access the action bar and other UI controls somewhat frequently, but not be bothered with any UI elements while flipping through content, IMMERSIVE is a good option for this use case.

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2. Solution

My solution is to set up your view ui in the onActivityCreated of your fragments.

My example taken from ImmersiveModeFragment.java sample.

@Override
public void onActivityCreated(Bundle savedInstanceState) {
    super.onActivityCreated(savedInstanceState);
    final View decorView = getActivity().getWindow().getDecorView();
    decorView.setOnSystemUiVisibilityChangeListener(
            new View.OnSystemUiVisibilityChangeListener() {
                @Override
                public void onSystemUiVisibilityChange(int i) {
                    hideSystemUI();
                }
            });
}

Create a separate method to manage the ui that you call from your OnSystemUiVisibilityChangeListener()

Taken from here non sticky immersion

private void hideSystemUI() {
    // Set the IMMERSIVE flag.
    // Set the content to appear under the system bars so that the content
    // doesn't resize when the system bars hide and show.
    mDecorView.setSystemUiVisibility(
        View.SYSTEM_UI_FLAG_LAYOUT_STABLE
        | View.SYSTEM_UI_FLAG_LAYOUT_HIDE_NAVIGATION
        | View.SYSTEM_UI_FLAG_LAYOUT_FULLSCREEN
        | View.SYSTEM_UI_FLAG_HIDE_NAVIGATION // hide nav bar
        | View.SYSTEM_UI_FLAG_FULLSCREEN // hide status bar
        | View.SYSTEM_UI_FLAG_IMMERSIVE);
}

You can then call this method again onResume.

onResume(){
    hideSystemUI();
}

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3. Alternate solution.

If sticky immersion is what you really want you need to try a different approach.

For sticky immersion

@Override
public void onWindowFocusChanged(boolean hasFocus) {
    super.onWindowFocusChanged(hasFocus);
    if (hasFocus) {
        decorView.setSystemUiVisibility(
            View.SYSTEM_UI_FLAG_LAYOUT_STABLE
            | View.SYSTEM_UI_FLAG_LAYOUT_HIDE_NAVIGATION
            | View.SYSTEM_UI_FLAG_LAYOUT_FULLSCREEN
            | View.SYSTEM_UI_FLAG_HIDE_NAVIGATION
            | View.SYSTEM_UI_FLAG_FULLSCREEN
            | View.SYSTEM_UI_FLAG_IMMERSIVE_STICKY);}
}

I hope this solves your problems.