android - Permanently hide Navigation Bar in an activity

Question

Is it possible to permanently remove the Navigation Bar on an activity? I want to remove the bar with the buttons that appear at the button of the screen on a tablet, not the Action Bar. Here.

I know it is not recommended to do that, I did not make this decision, but I need to do it. On my layout, there is another button to leave the activity. The rest of my app can have and does have the Navigation Bar.

I found this code and adapted it a little bit. The problem is that even when I hide the Navigation Bar, there is a black space left behind. I guess the system calculates the screen size having into account the navigation bar?

public static class Content extends ImageView implements View.OnSystemUiVisibilityChangeListener, View.OnClickListener, ActionBar.OnMenuVisibilityListener {
    Activity mActivity;
    TextView mTitleView;
    Button mPlayButton;
    SeekBar mSeekView;
    boolean mAddedMenuListener;
    boolean mMenusOpen;
    boolean mPaused;
    boolean mNavVisible;
    int mLastSystemUiVis;

    Runnable mNavHider = new Runnable() {
        @Override public void run() {
            setNavVisibility(false);
        }
    };

    public Content(Context context, AttributeSet attrs) {
        super(context, attrs);
        setOnSystemUiVisibilityChangeListener(this);
        setOnClickListener(this);
    }

    public void init(Activity activity, TextView title, Button playButton,
            SeekBar seek) {
        // This called by the containing activity to supply the surrounding
        // state of the video player that it will interact with.
        mActivity = activity;
        mTitleView = title;
        mPlayButton = playButton;
        mSeekView = seek;
        mPlayButton.setOnClickListener(this);
        setPlayPaused(true);
    }

    @Override protected void onAttachedToWindow() {
        super.onAttachedToWindow();
        if (mActivity != null) {
            mAddedMenuListener = true;
            mActivity.getActionBar().addOnMenuVisibilityListener(this);
        }
    }

    @Override protected void onDetachedFromWindow() {
        super.onDetachedFromWindow();
        if (mAddedMenuListener) {
            mActivity.getActionBar().removeOnMenuVisibilityListener(this);
        }
    }

    @Override public void onSystemUiVisibilityChange(int visibility) {
        // Detect when we go out of nav-hidden mode, to clear our state
        // back to having the full UI chrome up.  Only do this when
        // the state is changing and nav is no longer hidden.
        int diff = mLastSystemUiVis ^ visibility;
        mLastSystemUiVis = visibility;
        if ((diff&SYSTEM_UI_FLAG_HIDE_NAVIGATION) != 0
                && (visibility&SYSTEM_UI_FLAG_HIDE_NAVIGATION) == 0) {
            setNavVisibility(true);
        }
    }

    @Override protected void onWindowVisibilityChanged(int visibility) {
        super.onWindowVisibilityChanged(visibility);

        // When we become visible or invisible, play is paused.
        setPlayPaused(true);
    }

    @Override public void onClick(View v) {
        if (v == mPlayButton) {
            // Clicking on the play/pause button toggles its state.
            setPlayPaused(!mPaused);
        } else {
            // Clicking elsewhere makes the navigation visible.
            setNavVisibility(true);
        }
    }

    @Override public void onMenuVisibilityChanged(boolean isVisible) {
        mMenusOpen = isVisible;
        setNavVisibility(true);
    }

    void setPlayPaused(boolean paused) {
        mPaused = paused;
        mPlayButton.setText(paused ? R.string.play : R.string.pause);
        setKeepScreenOn(!paused);
        setNavVisibility(true);
    }

    void setNavVisibility(boolean visible) {
        int newVis = SYSTEM_UI_FLAG_LAYOUT_FULLSCREEN
                | SYSTEM_UI_FLAG_LAYOUT_HIDE_NAVIGATION
                | SYSTEM_UI_FLAG_LAYOUT_STABLE;
        if (!visible) {
            newVis |= SYSTEM_UI_FLAG_LOW_PROFILE | SYSTEM_UI_FLAG_FULLSCREEN
                    | SYSTEM_UI_FLAG_HIDE_NAVIGATION;
        }

        // If we are now visible, schedule a timer for us to go invisible.
        if (visible) {
            Handler h = getHandler();
            if (h != null) {
                h.removeCallbacks(mNavHider);
                if (!mMenusOpen && !mPaused) {
                    // If the menus are open or play is paused, we will not auto-hide.
                    h.postDelayed(mNavHider, 1500);
                }
            }
        }

        // Set the new desired visibility.
        setSystemUiVisibility(newVis);
        mTitleView.setVisibility(visible ? VISIBLE : INVISIBLE);
        mPlayButton.setVisibility(visible ? VISIBLE : INVISIBLE);
        mSeekView.setVisibility(visible ? VISIBLE : INVISIBLE);
    }

}

Answer 1

There is a solution starting with KitKat (4.4.2), called Immersive Mode: https://developer.android.com/training/system-ui/immersive.html

Basically, you should add this code to your onResume() method:

View decorView = getWindow().getDecorView();
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);