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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.

Permanently hide bottom bar

I am working on custom screen lock app where we need to full screen view hiding the top and bottom bars completely. The app is for Android phones only and not tablets. I achieved this partially by using Immersive mode but the issue is the bottom bar & top appears for few seconds on touching bottom or top of the screen.
Below is the code in my activity to do this :
final int flags = 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;
getWindow().getDecorView().setSystemUiVisibility(flags);
I have tried various options but unable to hide the bars permanently. Please advise.

Android paused app preview image black

In the list of the paused apps, Android usually shows a small preview image of the app.
However, the preview image is black when I use the following way to hide the navigation bar:
uiOptions = View.SYSTEM_UI_FLAG_LAYOUT_STABLE
| View.SYSTEM_UI_FLAG_LAYOUT_FULLSCREEN
| View.SYSTEM_UI_FLAG_HIDE_NAVIGATION
| View.SYSTEM_UI_FLAG_FULLSCREEN
| View.SYSTEM_UI_FLAG_IMMERSIVE_STICKY
| View.SYSTEM_UI_FLAG_LAYOUT_HIDE_NAVIGATION;
View decorView = getWindow().getDecorView();
decorView.setSystemUiVisibility(uiOptions);
If I remove the last two options, the preview is shown correctly. Keep one and the preview is black.
Is this a bug or are there any reasons for this? Are there any workarounds?
Edit: I would like too add that I also see this behaviour on other games that hide the navigation bar, like Plants vs. Zoombies 2....but that could be on purpose.

When Using Immersive Mode a line appears

I'm trying to use the immersive mode introduced in Android 4.4. I use this code to set the visibility and it works exactly how I want it to:
View decorView = getWindow().getDecorView();
int uiOptions = //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_STICKY;
decorView.setSystemUiVisibility(uiOptions);
However, it puts a line on the display. I have a screenshot but cannot post it because this is my first question. I have no idea what it is or how to get rid of it. Can anyone help?