如何再次隐藏navgationBar？

// 隐藏导航栏
getWindow().addFlags(WindowManager.LayoutParams.FLAG_FULLSCREEN);
// 显示导航栏
getWindow().clearFlags(WindowManager.LayoutParams.FLAG_FULLSCREEN);

// 隐藏导航栏
navigationController?.setNavigationBarHidden(true, animated: true)
// 显示导航栏
navigationController?.setNavigationBarHidden(false, animated: true)

<style name="AppTheme.NoActionBar">
    <item name="windowActionBar">false</item>
    <item name="windowNoTitle">true</item>
</style>

<activity
    android:name=".MainActivity"
    android:theme="@style/AppTheme.NoActionBar">
</activity>

// 隐藏导航栏
View decorView = getWindow().getDecorView();
int flags = View.SYSTEM_UI_FLAG_HIDE_NAVIGATION | View.SYSTEM_UI_FLAG_FULLSCREEN;
decorView.setSystemUiVisibility(flags);
// 显示导航栏
decorView.setSystemUiVisibility(View.SYSTEM_UI_FLAG_VISIBLE);