How to hide navigation bar when i press action bar

问题:

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);
}

回答1:

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.