Hiding the Navigation Bar

https://developer.android.com/training/system-ui/navigation.html

This lesson describes how to hide the navigation bar, which was introduced inAndroid 4.0 (API level 14).

Even though this lesson focuses on hiding thenavigation bar, you should design your app to hide the status barat the same time, as described in Hiding the Status Bar.Hiding the navigation and status bars (while still keeping them readily accessible)lets the content use the entire display space, thereby providing a more immersiveuser experience.

Figure 1. Navigation bar.

Hide the Navigation Bar on 4.0 and Higher

You can hide the navigation bar on Android 4.0 and higher using theSYSTEM_UI_FLAG_HIDE_NAVIGATION flag. This snippet hides boththe navigation bar and the status bar:

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);

Note the following:

• 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 youwant to hide the bars again. See Responding to UI Visibility Changes for adiscussion of how to listen for UI visibility changes so that your app canrespond accordingly.
• Where you set the UI flags makes a difference. If you hide the system bars in your activity's onCreate() method and the user presses Home, the system bars will reappear. When the user reopens the activity, onCreate()won't get called, so the system bars will remain visible. If you want system UI changes topersist as the user navigates in and out of your activity, set UI flags inonResume()or onWindowFocusChanged().
• The method setSystemUiVisibility() only has an effect if the view you call it from is visible.
• Navigating away from the view causes flags set with setSystemUiVisibility() to be cleared.

Make Content Appear Behind the Navigation Bar

On Android 4.1 and higher, you can set your application's content to appear behindthe navigation bar, so that the content doesn't resize as the navigation bar hides andshows. To do this, useSYSTEM_UI_FLAG_LAYOUT_HIDE_NAVIGATION.You may also need to useSYSTEM_UI_FLAG_LAYOUT_STABLE to help your app maintain astable layout.

When you use this approach, it becomes your responsibility to ensure that critical partsof your app's UI don't end up getting covered by system bars. For morediscussion of this topic, see the Hiding the Status Bar lesson.

Next: Using Immersive Full-Screen Mode