Develop Reference

Going full-screen and exiting that mode, makes status bar disappear

I am going from one context executing this to go into full screen mode..
activity.window.decorView.systemUiVisibility = (View.SYSTEM_UI_FLAG_IMMERSIVE_STICKY
or View.SYSTEM_UI_FLAG_LAYOUT_STABLE
or View.SYSTEM_UI_FLAG_LAYOUT_HIDE_NAVIGATION
or View.SYSTEM_UI_FLAG_LAYOUT_FULLSCREEN
or View.SYSTEM_UI_FLAG_HIDE_NAVIGATION
or View.SYSTEM_UI_FLAG_FULLSCREEN)
Then when I leave the full-screen mode I call this...
getActivity().window?.decorView?.systemUiVisibility = View.SYSTEM_UI_FLAG_VISIBLE
Problem is.. the status bar up top is gone. What do I do?
edit It looks like the status bar does appear, but it's ending up behind the main content.

Hack solution rather than playing with individual flags outright...
I just grabbed the int value of decorView.systemUiVisibility and set it to that when I dismiss my full screen mode. This resolved it...

How to remove back button from navigation bar?

I thought that is a solution for that but I cannot find it. I know that I can disable back button by overriding onBackPress() method and not call super.onBackPress() but it only disable, I want to remove/hide from navigation bar this button.
And I known that on some device where the back button is a part of hardware it can be done.
To be clear I mean arrow on below screen:

You can find solution in the documentation.
View decorView = getWindow().getDecorView();
// Hide both the navigation bar and the status bar.
// SYSTEM_UI_FLAG_FULLSCREEN is only available on Android 4.1 and higher, but as
// a general rule, you should design your app to hide the status bar whenever you
// hide the navigation bar.
int uiOptions = View.SYSTEM_UI_FLAG_HIDE_NAVIGATION
| View.SYSTEM_UI_FLAG_FULLSCREEN;
decorView.setSystemUiVisibility(uiOptions);
and this code should be placed in onCreate() method in the Activity after initializing all UI elements.

use this code in your onCreate() method : to hide
View bView = getWindow().getDecorView();
bView.setSystemUiVisibility(View.SYSTEM_UI_FLAG_HIDE_NAVIGATION);

How to permanently hide navigation bar in android application?

I have a problem hiding navigation bar at the bottom of the screen in android.
Every solution I've tried doesn't work exactly as I want it to work, except one.
Modifying build.prop with new entry 'qemu.hw.mainkeys=1' worked ok, but it disables navigation bar for whole android system.
Is there possibility to disable navigation bar like this only for one app?

Try this:
View decorView = getWindow().getDecorView();
// Hide both the navigation bar and the status bar.
// SYSTEM_UI_FLAG_FULLSCREEN is only available on Android 4.1 and higher, but as
// a general rule, you should design your app to hide the status bar whenever you
// hide the navigation bar.
int uiOptions = View.SYSTEM_UI_FLAG_HIDE_NAVIGATION | View.SYSTEM_UI_FLAG_FULLSCREEN;
decorView.setSystemUiVisibility(uiOptions);
(Source)

View decorView = getWindow().getDecorView();
int uiOptions = View.SYSTEM_UI_FLAG_HIDE_NAVIGATION | View.SYSTEM_UI_FLAG_FULLSCREEN | View.SYSTEM_UI_FLAG_IMMERSIVE_STICKY;
decorView.setSystemUiVisibility(uiOptions);
Use this code in onCreate(), it will hide status bar and navigation bar until users swipe down from top of the screen

How to disable naviagation bar in Android LockScreen App like CM locker and OS8 lock screen

I tried setting systemUIView(View.GONE) and use Immersive Full-Screen Mode. But users can always get the naviagtion bar back by touching the bottom of the screen. The apps i mentioned above are able to hide it without root or setting default launcher.

Okay, I found a solution finally and here is how it's done:
Use SYSTEM_UI_FLAG_IMMERSIVE_STICKY to hide the navigation bar as follow, you may put the code inside onResume of your activity
View decorView = getWindow().getDecorView();
int uiOptions = View.SYSTEM_UI_FLAG_HIDE_NAVIGATION |View.SYSTEM_UI_FLAG_IMMERSIVE_STICKY;
decorView.setSystemUiVisibility(uiOptions);
Then, add a system error window using WindowManger and overlay it on top of everything
you can put this unescapable view anywhere you like, but if you want to do it while users locked the screen, add this flag:
getWindow().setFlags(WindowManager.LayoutParams.FLAG_SHOW_WHEN_LOCKED, WindowManager.LayoutParams.FLAG_SHOW_WHEN_LOCKED);
Et voilà

Well I've never achieved this but it seems that you will need to set some other flags to get this kind of view :
When you use the SYSTEM_UI_FLAG_IMMERSIVE flag, it hides the system bars based on what other UI flags you have set (SYSTEM_UI_FLAG_HIDE_NAVIGATION, SYSTEM_UI_FLAG_FULLSCREEN, or both). When the user swipes inward in a system bars region, the system bars reappear and remain visible.
Here is a snippet that you can use to set these flags :
// This snippet hides the system bars.
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);
}
// This snippet shows the system bars. It does this by removing all the flags
// except for the ones that make the content appear under the system bars.
private void showSystemUI() {
mDecorView.setSystemUiVisibility(
View.SYSTEM_UI_FLAG_LAYOUT_STABLE
| View.SYSTEM_UI_FLAG_LAYOUT_HIDE_NAVIGATION
| View.SYSTEM_UI_FLAG_LAYOUT_FULLSCREEN);
}
For more information go check Using Immersive Full-screen Mode from the android developer website.
Hope this help.

How to hide navigation bar when i press action bar menu in Android

I hide the navigation bar (see below) but when I press the menu button on action bar the navigation bar immediately appear.
Can I hide nav. bar permanently?
#Override
protected void onCreate(Bundle savedInstanceState) {
super.onCreate(savedInstanceState);
getWindow().setFlags(WindowManager.LayoutParams.FLAG_FULLSCREEN, WindowManager.LayoutParams.FLAG_FULLSCREEN);
getWindow().getDecorView().setSystemUiVisibility(
View.SYSTEM_UI_FLAG_LAYOUT_STABLE |
View.SYSTEM_UI_FLAG_LAYOUT_HIDE_NAVIGATION |
View.SYSTEM_UI_FLAG_HIDE_NAVIGATION |
View.SYSTEM_UI_FLAG_IMMERSIVE_STICKY);
setContentView(R.layout.activity_fomenu);
}

Take a look at the documentation. It says to hide the navigation use
View decorView = getWindow().getDecorView();
// Hide both the navigation bar and the status bar.
// SYSTEM_UI_FLAG_FULLSCREEN is only available on Android 4.1 and higher, but as
// a general rule, you should design your app to hide the status bar whenever you
// hide the navigation bar.
int uiOptions = View.SYSTEM_UI_FLAG_HIDE_NAVIGATION
| View.SYSTEM_UI_FLAG_FULLSCREEN;
decorView.setSystemUiVisibility(uiOptions);
You're already doing that. But then it says
With this approach, touching anywhere on the screen causes the navigation bar (and status bar) to reappear and remain visible. The user interaction causes the flags to be be cleared. Once the flags have been cleared, your app needs to reset them if you want to hide the bars again. See Responding to UI Visibility Changes for a discussion of how to listen for UI visibility changes so that your app can respond accordingly.
This means that you will have to reset the flags when the user selects the options menu. A sample code is also given here.