How to make Android Splash Screen Fullscreen

This is my code. I am following a tutorial on Youtube. When I use android:theme="@android:style/Theme.Light.NoTitleBar.Fullscreen" the screen does not show the splash screen and shows a blank screen instead. My code is as the following.

<activity
   android:name="com.nowate.customerapp.activity.SplashActivity"
   android:screenOrientation="portrait"
   android:theme="@style/AppTheme.NoActionBar" >
   <intent-filter>
      <action android:name="android.intent.action.MAIN" />

      <category android:name="android.intent.category.LAUNCHER" />
   </intent-filter>
</activity>

This is the proper way to add a splash screen to your app. It doesn't take any fixed time to display it because it is showing while the app really loads.

1. Declare a new theme in styles.xml:

 <style name="SplashTheme" parent="Theme.AppCompat.Light.NoActionBar">
        <item name="android:windowBackground">@drawable/splash_screen</item>
        <item name="android:windowFullscreen">true</item>
        <item name="android:windowTranslucentNavigation">true</item>
        <item name="android:windowDrawsSystemBarBackgrounds">true</item>
 </style>

2. Set the theme in AndroidManifest to your launcher activity (don't create a new activity just for a splash screen):

<activity
   android:name="com.nowate.customerapp.activity.MainActivity"
   android:screenOrientation="portrait"
    android:theme="@style/SplashTheme" >
   <intent-filter>
      <action android:name="android.intent.action.MAIN" />

      <category android:name="android.intent.category.LAUNCHER" />
   </intent-filter>
</activity>

3. In your MainActivity in the onCreate() method set the original theme befor setting the layout:

setTheme(R.style.AppTheme);
super.onCreate(savedInstanceState);
setContentView(R.layout.activity_main);

4. Example of splash screen drawable ("ic_loading" is a vector):

<?xml version="1.0" encoding="utf-8"?>
<layer-list xmlns:android="http://schemas.android.com/apk/res/android">
    <item>
        <shape
            android:shape="rectangle">
            <solid android:color="@color/black" />
        </shape>
    </item>
    <item
        android:gravity="center"
        android:drawable="@drawable/ic_loading"/>
</layer-list>