Android file sharing

I’am developing an app in which I want to share a binary file created in the app. For sharing the file I want to use the Android Sharesheet as is recommended.

So in my .pro file I have added QT += androidextras

I have a .java file, public class QShareUtils, package org.mnc.utils; , with the static method

    public static void sendFile(String filePath) {
        Intent sendIntent = new Intent();
        sendIntent.setAction(Intent.ACTION_SEND);

        // We only share / send .fit files
        sendIntent.setType("application/octet-stream");
        
        Uri uriToFile = Uri.fromFile(new File(filePath));
        sendIntent.putExtra(Intent.EXTRA_STREAM, uriToFile);

        sendIntent.addFlags(Intent.FLAG_GRANT_READ_URI_PERMISSION);
        sendIntent.addFlags(Intent.FLAG_GRANT_WRITE_URI_PERMISSION);
        
        Intent shareIntent = Intent.createChooser(sendIntent, "Share .fit file");
        Activity activity = new Activity();
        activity.startActivity(shareIntent);
    }

and in my .cpp file I call this method

void AndroidShareUtils::sendFile(const QString &filePath, const QString &title, const QString &mimeType)
{
    Q_UNUSED(title)
    Q_UNUSED(mimeType)

    QAndroidJniObject jsText = QAndroidJniObject::fromString(filePath);
    QAndroidJniObject::callStaticMethod<void>("utils/QShareUtils",
                                                  "sendFile",
                                                  "(Ljava/lang/String;)V",
                                                  jsText.object<jstring>());

}

I get no compile errors and can install the app on my phone. I can check that the function is called but obviously nothing happens.

Remarkeble is that in the .cpp source I get the warning: warning instantiation of function ‘QAndroidJniObject::callStaticMethod<void>’ required here, but no definition is available

I do not know why this is showing up although this probably needs attention.

I’am developing on W10 Qt Creator 4.10.2 and use kit Android for arm64-v8a(Clang Qt 5.13.2 …)

I searched for hours but have no clou as what to try next. If anyone has any ideas I would appreciate your suggestion(s).