Immersive fullscreen on Android 11

For compatibility, use WindowCompat and WindowInsetsControllerCompat. You'll need to upgrade your gradle dependency for androidx.core to at least 1.6.0-alpha03 so that there will be support for setSystemBarsBehavior on SDK < 30. mainContainer is the top-level ConstraintLayout in my activity.

private fun hideSystemUI() {
    WindowCompat.setDecorFitsSystemWindows(window, false)
    WindowInsetsControllerCompat(window, mainContainer).let { controller ->
        controller.hide(WindowInsetsCompat.Type.systemBars())
        controller.systemBarsBehavior = WindowInsetsControllerCompat.BEHAVIOR_SHOW_TRANSIENT_BARS_BY_SWIPE
    }
}

private fun showSystemUI() {
    WindowCompat.setDecorFitsSystemWindows(window, true)
    WindowInsetsControllerCompat(window, mainContainer).show(WindowInsetsCompat.Type.systemBars())
}

You can find out more information about WindowInsets by watching this YouTube video

EDIT:

I didn't consider display cutouts or in-display cameras in this answer previously. In the app theme style, i added the following to display my content above the cutout (to the top of the screen when in portrait mode):

<item name="android:windowLayoutInDisplayCutoutMode">shortEdges</item>

You can read more at this link: Display Cutout

Here's the answer in Kotlin, in case if you don't want to increase the size of your app by using the androidx library.

private fun setFullscreen() {
    if (Build.VERSION.SDK_INT >= Build.VERSION_CODES.P) {
        window.attributes.layoutInDisplayCutoutMode =
            WindowManager.LayoutParams.LAYOUT_IN_DISPLAY_CUTOUT_MODE_SHORT_EDGES
    }

    if (Build.VERSION.SDK_INT >= Build.VERSION_CODES.R) {
        window.setDecorFitsSystemWindows(false)
        window.insetsController?.apply {
            hide(WindowInsets.Type.statusBars() or WindowInsets.Type.navigationBars())
            systemBarsBehavior = WindowInsetsController.BEHAVIOR_SHOW_TRANSIENT_BARS_BY_SWIPE
        }
    } else if (Build.VERSION.SDK_INT >= Build.VERSION_CODES.KITKAT) {
        @Suppress("DEPRECATION")
        window.decorView.systemUiVisibility = (View.SYSTEM_UI_FLAG_FULLSCREEN
                or View.SYSTEM_UI_FLAG_HIDE_NAVIGATION
                or View.SYSTEM_UI_FLAG_IMMERSIVE
                or View.SYSTEM_UI_FLAG_LAYOUT_STABLE
                or View.SYSTEM_UI_FLAG_LAYOUT_FULLSCREEN
                or View.SYSTEM_UI_FLAG_LAYOUT_HIDE_NAVIGATION)
    }
}

Call the function your activity's onCreate method.

ORIGINAL ANSWER:

As documentation suggests, you should use WindowInsetsController.

getWindow().setDecorFitsSystemWindows(false);
WindowInsetsController controller = getWindow().getInsetsController();
if (controller != null) {
    controller.hide(WindowInsets.Type.statusBars() | WindowInsets.Type.navigationBars());
    controller.setSystemBarsBehavior(WindowInsetsController.BEHAVIOR_SHOW_TRANSIENT_BARS_BY_SWIPE);
}

For the deprecation, you can try the below code. Worked for me.

  if (Build.VERSION.SDK_INT >= Build.VERSION_CODES.R) {
        final WindowInsetsController controller = getWindow().getInsetsController();

        if (controller != null)
            controller.hide(WindowInsets.Type.statusBars());
    }
    else {
        //noinspection deprecation
                getWindow().getDecorView().setSystemUiVisibility(
            View.SYSTEM_UI_FLAG_FULLSCREEN
                    | View.SYSTEM_UI_FLAG_HIDE_NAVIGATION
                    | View.SYSTEM_UI_FLAG_IMMERSIVE
                    | View.SYSTEM_UI_FLAG_LAYOUT_STABLE
                    | View.SYSTEM_UI_FLAG_LAYOUT_FULLSCREEN
                    | View.SYSTEM_UI_FLAG_LAYOUT_HIDE_NAVIGATION);
    }

This works for me, mixed two answers:

First create method :

private void setFullScreen(){
    if (Build.VERSION.SDK_INT >= Build.VERSION_CODES.R) {
        getWindow().setDecorFitsSystemWindows(false);
        WindowInsetsController controller = getWindow().getInsetsController();
        if(controller != null) {
            controller.hide(WindowInsets.Type.statusBars() | WindowInsets.Type.navigationBars());
            controller.setSystemBarsBehavior(WindowInsetsController.BEHAVIOR_SHOW_TRANSIENT_BARS_BY_SWIPE);
        }
    }
    else {
        //noinspection deprecation
        getWindow().getDecorView().setSystemUiVisibility(
                View.SYSTEM_UI_FLAG_FULLSCREEN
                        | View.SYSTEM_UI_FLAG_HIDE_NAVIGATION
                        | View.SYSTEM_UI_FLAG_IMMERSIVE
                        | View.SYSTEM_UI_FLAG_LAYOUT_STABLE
                        | View.SYSTEM_UI_FLAG_LAYOUT_FULLSCREEN
                        | View.SYSTEM_UI_FLAG_LAYOUT_HIDE_NAVIGATION);
    }
}

then on create just call it after setContentView like this :

  @Override
    protected void onCreate(Bundle savedInstanceState) {
        super.onCreate(savedInstanceState);
        setContentView(R.layout.activity_main_menu);
        setFullScreen();
    }

and it works like a charm :D

I'm using this one, work perfectly for all Android version

 if (Build.VERSION.SDK_INT >= Build.VERSION_CODES.R) {
            window.setDecorFitsSystemWindows(false)
            val controller = window.insetsController
            if (controller != null) {
                controller.hide(WindowInsets.Type.statusBars() or WindowInsets.Type.navigationBars())
                controller.systemBarsBehavior = WindowInsetsController.BEHAVIOR_SHOW_TRANSIENT_BARS_BY_SWIPE
            }
        } else {
            // All below using to hide navigation bar
            val currentApiVersion = Build.VERSION.SDK_INT
            val flags = (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
                    or View.SYSTEM_UI_FLAG_IMMERSIVE_STICKY)

            // This work only for android 4.4+
            if (currentApiVersion >= Build.VERSION_CODES.KITKAT) {
                window.decorView.systemUiVisibility = 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
                val decorView = window.decorView
                decorView.setOnSystemUiVisibilityChangeListener { visibility: Int ->
                    if (visibility and View.SYSTEM_UI_FLAG_FULLSCREEN == 0) {
                        decorView.systemUiVisibility = flags
                    }
                }
            }
        }

For fullscreen

Hide StatusBar

private void hideSystemBars() {
    WindowCompat.setDecorFitsSystemWindows(getWindow(), false);
    WindowInsetsControllerCompat windowInsetsController = ViewCompat.getWindowInsetsController(getWindow().getDecorView());
    if (windowInsetsController == null) {
        return;
    }
    // Configure the behavior of the hidden system bars
    windowInsetsController.setSystemBarsBehavior(WindowInsetsControllerCompat.BEHAVIOR_SHOW_TRANSIENT_BARS_BY_SWIPE);
    // Hide both the status bar and the navigation bar
    windowInsetsController.hide(WindowInsetsCompat.Type.systemBars());
}

show StatusBar

private void showSystemBars() {
    WindowCompat.setDecorFitsSystemWindows(getWindow(), false);
    WindowInsetsControllerCompat windowInsetsController = ViewCompat.getWindowInsetsController(getWindow().getDecorView());
    if (windowInsetsController == null) {
        return;
    }
    // Configure the behavior of the hidden system bars
    windowInsetsController.setSystemBarsBehavior(WindowInsetsControllerCompat.BEHAVIOR_SHOW_TRANSIENT_BARS_BY_SWIPE);
    // Hide both the status bar and the navigation bar
    windowInsetsController.show(WindowInsetsCompat.Type.systemBars());
}

for top camera cutting in full screen mode

<item name="android:windowLayoutInDisplayCutoutMode" tools:ignore="NewApi">shortEdges</item>

According to Chris Banes @ Android Developers official youtube channel use following code

class MainActivity : AppCompatActivity() {
    private lateinit var binding: ActivityMainBinding
    private lateinit var view: View

    override fun onCreate(savedInstanceState: Bundle?) {
        super.onCreate(savedInstanceState)
        binding = ActivityMainBinding.inflate(layoutInflater)
        view = binding.root
        setContentView(view)
    }

    override fun onWindowFocusChanged(hasFocus: Boolean) {
        super.onWindowFocusChanged(hasFocus)
        if (hasFocus) hideSystemUI()
    }

    private fun hideSystemUI() {
        if (Build.VERSION.SDK_INT >= Build.VERSION_CODES.R) {
            // Tell the window that we want to handle/fit any system windows
            WindowCompat.setDecorFitsSystemWindows(window, false)

            val controller = view.windowInsetsController

            // Hide the keyboard (IME)
            controller?.hide(WindowInsets.Type.ime())

            // Sticky Immersive is now ...
            controller?.systemBarsBehavior = BEHAVIOR_SHOW_TRANSIENT_BARS_BY_SWIPE

            // When we want to hide the system bars
            controller?.hide(WindowInsets.Type.systemBars())

            /*val flag = WindowInsets.Type.statusBars()
            WindowInsets.Type.navigationBars()
            WindowInsets.Type.captionBar()
            window?.insetsController?.hide(flag)*/
        } else {
            //noinspection
            @Suppress("DEPRECATION")
            // For "lean back" mode, remove SYSTEM_UI_FLAG_IMMERSIVE.
            window.decorView.systemUiVisibility = (View.SYSTEM_UI_FLAG_IMMERSIVE_STICKY
                // Set the content to appear under the system bars so that the
                // content doesn't resize when the system bars hide and show.
                or View.SYSTEM_UI_FLAG_LAYOUT_STABLE
                or View.SYSTEM_UI_FLAG_LAYOUT_HIDE_NAVIGATION
                or View.SYSTEM_UI_FLAG_LAYOUT_FULLSCREEN
                // Hide the nav bar and status bar
                or View.SYSTEM_UI_FLAG_HIDE_NAVIGATION
                or View.SYSTEM_UI_FLAG_FULLSCREEN)
        }
    }
}

Here is Sample Link User interface sample

//you can do it by the following simple method

public void FullScreencall() {
  if (Build.VERSION.SDK_INT < 19) {
    getWindow().getDecorView().setSystemUiVisibility(8);
  } else {
    getWindow().getDecorView().setSystemUiVisibility(InputDeviceCompat.SOURCE_TOUCHSCREEN);       
  }
}