Several classes in android manifest.

[Alexorleon]

Hello!
I wanted to hide ActionBar in android.

// java code
if(getSupportActionBar().isShowing()) {

    View decorView = getWindow().getDecorView();
    int uiOptions = View.SYSTEM_UI_FLAG_HIDE_NAVIGATION | View.SYSTEM_UI_FLAG_FULLSCREEN;
    decorView.setSystemUiVisibility(uiOptions);

    getSupportActionBar().hide();
} else {
    getSupportActionBar().show();
}

To test this code, I created an empty project "Blanck Activity" in Android Studio. I added code to the button. Works great.
Now the implementation in Qt.

// main.cpp
QAndroidJniObject::callStaticMethod<void>("AndroidBar", "hideNavigationBar");

// AndroidBar.java
import android.view.View;
import android.util.Log;

public class AndroidBar extends org.qtproject.qt5.android.bindings.QtActivity
{
    private static final String TAG = AndroidBar.class.getSimpleName();

    public static void hideNavigationBar() {

        Log.d(TAG, "Hide navigation bar");

        View decorView = getWindow().getDecorView();
        int uiOptions = View.SYSTEM_UI_FLAG_HIDE_NAVIGATION | View.SYSTEM_UI_FLAG_FULLSCREEN;
        decorView.setSystemUiVisibility(uiOptions);
    }
}

But there is an error:
non-static method getWindow() cannot be referenced from a static context

Then I decided to create a separate class.

// AndroidBar.java
import android.util.Log;

public class AndroidBar extends org.qtproject.qt5.android.bindings.QtActivity
{
    private static final String TAG = AndroidBar.class.getSimpleName();

    public static void hideNavigationBar() {

        Log.d(TAG, "Hide navigation bar");

        MyTest test = new MyTest();
        test.hideBar();

        test = null;
    }
}

// MyTest.java
import android.view.View;
import android.util.Log;

public class MyTest extends org.qtproject.qt5.android.bindings.QtActivity
{
    private String TAG = AndroidBar.class.getSimpleName();

    public void hideBar() {

        Log.d(TAG, "Hide bar");

        View decorView = getWindow().getDecorView();
        int uiOptions = View.SYSTEM_UI_FLAG_HIDE_NAVIGATION | View.SYSTEM_UI_FLAG_FULLSCREEN;
        decorView.setSystemUiVisibility(uiOptions);
    }
}

No errors, but the method is not called. In the Android Studio it works.

// .pro
android {
    QT += androidextras
    ANDROID_PACKAGE_SOURCE_DIR = $$PWD/android
    OTHER_FILES += android/AndroidManifest.xml \
    android/src/AndroidBar.java \
    android/src/MyTest.java
}

// AndroidManifest.xml
<application android:icon="@drawable/icon" android:label="@string/app_name" android:hardwareAccelerated="true" android:name="org.qtproject.qt5.android.bindings.QtApplication">
        <activity android:configChanges="orientation|uiMode|screenLayout|screenSize|smallestScreenSize|locale|fontScale|keyboard|keyboardHidden|navigation" 
				  android:label="@string/app_name" 
				  android:name="org.qtproject.qt5.android.bindings.QtActivity"
				  android:screenOrientation="landscape">

How to add this class to the project? Or are there other solutions?

[Alexorleon]

Create a new activity in your andrdoid/src folder subclassing QtActivity.
In this article, all explained in detail - https://www.kdab.com/qt-android-episode-7/.
At the end of the article there is the source code.

Add method in the class MyActivity.

@Override
    public void onWindowFocusChanged(boolean hasFocus)
    {
        Log.d("BLABLA", "Window focus changed");
        if (Build.VERSION.SDK_INT >= Build.VERSION_CODES.KITKAT) {

            if (hasFocus) {
                Log.d("SCREEN","IMMERSIVE MODE ACTIVE");
                getWindow().getDecorView().setSystemUiVisibility(
                            View.SYSTEM_UI_FLAG_LAYOUT_STABLE
                            | View.SYSTEM_UI_FLAG_LAYOUT_HIDE_NAVIGATION
                            | View.SYSTEM_UI_FLAG_LAYOUT_FULLSCREEN
                            | View.SYSTEM_UI_FLAG_HIDE_NAVIGATION
                            | View.SYSTEM_UI_FLAG_FULLSCREEN
                            | View.SYSTEM_UI_FLAG_IMMERSIVE_STICKY);}
        }

        if (!QtApplication.invokeDelegate(hasFocus).invoked)
            super.onWindowFocusChanged(hasFocus);
    }

Do not forget about it:

import android.os.Build;
import android.view.View;
import android.util.Log;

It works on version 4.4.