In Qt 5.2 it is possible to add custom views directly from Java (for example Google AdMob or other 3rd party views) by accessing getQtLayout() in the QtActivityDelegate. Then you can just call m_qtLayout.addView(m_adView for example. In Qt 5.3 this function is gone, instead there is a insertNativeView function which requires an id which I cannot reliably guarantee to not already be taken.

The ids are managed in androidjnimain.(cpp|h) and I'm not willing to use a C++ class to pass my Java stuff around to eventually do Java stuff again.