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how-to-hide-navigation-bar-permanently-in-android-activity

 private int currentApiVersion;
 
@Override 
@SuppressLint("NewApi") 
protected void onCreate(Bundle savedInstanceState)
{ 
    super.onCreate(savedInstanceState);
 
    currentApiVersion = android.os.Build.VERSION.SDK_INT;
 
    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;
 
    // This work only for android 4.4+ 
    if(currentApiVersion >= Build.VERSION_CODES.KITKAT)
    { 
 
        getWindow().getDecorView().setSystemUiVisibility(flags);
 
        // Code below is to handle presses of Volume up or Volume down. 
        // Without this, after pressing volume buttons, the navigation bar will 
        // show up and won't hide 
        final View decorView = getWindow().getDecorView();
        decorView
            .setOnSystemUiVisibilityChangeListener(new View.OnSystemUiVisibilityChangeListener()
            { 
 
                @Override 
                public void onSystemUiVisibilityChange(int visibility)
                { 
                    if((visibility & View.SYSTEM_UI_FLAG_FULLSCREEN) == 0)
                    { 
                        decorView.setSystemUiVisibility(flags);
                    } 
                } 
            }); 
    } 
 
} 
 
 
@SuppressLint("NewApi") 
@Override 
public void onWindowFocusChanged(boolean hasFocus)
{ 
    super.onWindowFocusChanged(hasFocus);
    if(currentApiVersion >= Build.VERSION_CODES.KITKAT && hasFocus)
    { 
        getWindow().getDecorView().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);
    } 
}