从mozilla找到解决方案，他们在这里做了一个扩展库

如果链接中断，这里是代码

/**
 * Retrieves a {@link WindowInsetsControllerCompat} for the top-level window decor view.
 */
fun Window.getWindowInsetsController(): WindowInsetsControllerCompat {
    return WindowInsetsControllerCompat(this, this.decorView)
}


/**
 * Attempts to call immersive mode using the View to hide the status bar and navigation buttons.
 * @param onWindowFocusChangeListener optional callback to ensure immersive mode is stable
 * Note that the callback reference should be kept by the caller and be used for [exitImmersiveModeIfNeeded] call.
 */
fun Activity.enterToImmersiveMode(
    onWindowFocusChangeListener: ViewTreeObserver.OnWindowFocusChangeListener? = null
) {
    window.addFlags(WindowManager.LayoutParams.FLAG_KEEP_SCREEN_ON)
    window.getWindowInsetsController().apply {
        hide(WindowInsetsCompat.Type.systemBars())
        systemBarsBehavior = WindowInsetsControllerCompat.BEHAVIOR_SHOW_TRANSIENT_BARS_BY_SWIPE
    }

    // We need to make sure system bars do not become permanently visible after interactions with content
    // see https://github.com/mozilla-mobile/fenix/issues/20240
    onWindowFocusChangeListener?.let {
        window.decorView.viewTreeObserver?.addOnWindowFocusChangeListener(it)
    }
}

/**
 * Attempts to come out from immersive mode using the View.
 * @param onWindowFocusChangeListener optional callback to ensure immersive mode is stable
 * Note that the callback reference should be kept by the caller and be the same used for [enterToImmersiveMode] call.
 */
@Suppress("DEPRECATION")
fun Activity.exitImmersiveModeIfNeeded(
    onWindowFocusChangeListener: ViewTreeObserver.OnWindowFocusChangeListener? = null
) {
    if (WindowManager.LayoutParams.FLAG_KEEP_SCREEN_ON and window.attributes.flags == 0) {
        // We left immersive mode already.
        return
    }
    onWindowFocusChangeListener?.let {
        window.decorView.viewTreeObserver?.removeOnWindowFocusChangeListener(it)
    }
    window.clearFlags(WindowManager.LayoutParams.FLAG_KEEP_SCREEN_ON)
    window.getWindowInsetsController().apply {
        show(WindowInsetsCompat.Type.systemBars())
    }
}

import androidx.core.view.WindowInsetsCompat.Type

fun Activity.fullscreen() {
    with(WindowInsetsControllerCompat(window, window.decorView)) {
        systemBarsBehavior = WindowInsetsControllerCompat.BEHAVIOR_SHOW_BARS_BY_SWIPE
        hide(Type.systemBars())
    }
}

fun Activity.exitFullscreen() {
    WindowInsetsControllerCompat(window, window.decorView).show(Type.systemBars())
}

 protected void onCreate(Bundle savedInstanceState) {
    requestWindowFeature(Window.FEATURE_NO_TITLE);
    super.onCreate(savedInstanceState);
    getWindow().setFlags(WindowManager.LayoutParams.FLAG_FULLSCREEN,WindowManager.LayoutParams.FLAG_FULLSCREEN);
    setContentView(R.layout.activity_splash_screen);
    getSupportActionBar().hide();

}

主题

    <style name="Theme.FluidWallpaper.FullScreen" parent="@style/Theme.AppCompat.Light.NoActionBar">
    <item name="android:windowFullscreen">true</item>
    <item name="android:windowTranslucentStatus">true</item>
    <item name="android:windowTranslucentNavigation">true</item>
    <item name="android:statusBarColor">@android:color/transparent</item>
    <item name="android:navigationBarColor">@android:color/transparent</item>
    <item name="android:windowLayoutInDisplayCutoutMode" tools:targetApi="o_mr1">shortEdges</item>
     </style>

安卓清单

   <activity android:exported="false"
        android:name=".FullScreenActivity"
        android:screenOrientation="fullSensor"
        android:theme="@style/Theme.FluidWallpaper.FullScreen"/>

用kotlin是这样做的:

class LoginActivity : AppCompatActivity() {

    override fun onCreate(savedInstanceState: Bundle?) {
        super.onCreate(savedInstanceState)
        setContentView(R.layout.activity_login)
        window.decorView.systemUiVisibility =
                View.SYSTEM_UI_FLAG_LAYOUT_STABLE or
                View.SYSTEM_UI_FLAG_LAYOUT_FULLSCREEN or
                View.SYSTEM_UI_FLAG_FULLSCREEN

    }
}

身临其境的模式

沉浸式模式适用于用户需要与屏幕进行大量交互的应用程序。例如游戏、浏览图库中的图像或阅读分页内容(如书籍或演示文稿中的幻灯片)。为此，只需添加这几行:

View.SYSTEM_UI_FLAG_HIDE_NAVIGATION or
View.SYSTEM_UI_FLAG_LAYOUT_HIDE_NAVIGATION

粘性身临其境

在常规的沉浸式模式下，每当用户从边缘滑动时，系统都会负责显示系统条——你的应用程序甚至不会意识到这个手势发生了。因此，如果用户可能真的需要从屏幕边缘滑动作为主要应用体验的一部分——比如在玩一款需要大量滑动的游戏或使用绘图应用时——你应该启用“粘性”沉浸模式。

View.SYSTEM_UI_FLAG_IMMERSIVE_STICKY

有关更多信息:启用全屏模式

如果你使用键盘，有时会发生状态栏显示时，键盘显示。在这种情况下，我通常将此添加到我的style xml

styles.xml

<style name="FullScreen" parent="AppTheme">
    <item name="android:windowFullscreen">true</item>
</style>

还有这一行到我的载货单上

<activity
        android:name=".ui.login.LoginActivity"
        android:label="@string/title_activity_login"
        android:theme="@style/FullScreen">

截至2022年

    if (Build.VERSION.SDK_INT >= Build.VERSION_CODES.R) {
        window.decorView.windowInsetsController?.hide(WindowInsets.Type.systemBars())
    } else {
        @Suppress("DEPRECATION") // Older API support
        window.decorView.systemUiVisibility = (View.SYSTEM_UI_FLAG_IMMERSIVE
                or 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)
    }