Set orientation on iOS at runtime

[peter-70]

I have an app with the following settings in the plist file:

   <key>UISupportedInterfaceOrientations</key>
   <array>
        <string>UIInterfaceOrientationPortrait</string>
        <string>UIInterfaceOrientationPortraitUpsideDown</string>
   </array>

They are the right settings, we need in our project.

But I have one and only part as qml-view with a camera (for a barcode-scanner).
These should be shown in all orientations, but at least landscape-orientation (left and right).

I try to set this at runtime with a call from my c++ code:

void MobileScreenOrientation::SetOrientation()
{
//    NSNumber *value = [NSNumber numberWithInt:UIInterfaceOrientationLandscapeRight];
//    [[UIDevice currentDevice] setValue:value forKey:@"orientation"];

    [[UIDevice currentDevice] setValue:@(UIInterfaceOrientationLandscapeLeft) forKey:@"orientation"];
    [UINavigationController attemptRotationToDeviceOrientation];
}

but it it doesn't work. The orientation in my qml is still portrait.
Can you help me, how can I set the landscape orientation on iOS at runtime, quasi manually?

Thanks!