title: Qt 5.7 for Android main C++ thread not running continously
body: <p>I've had a hell of time converting an Android project that worked in Qt 5.1 through 5.5 over to v5.7.  The first major problem was that it wouldn't even start the app, see: <a href="https://stackoverflow.com/questions/40920822/java-executes-but-not-c-in-qt-5-7-for-android-worked-in-prior-qt">Java executes but not C++ in Qt 5.7 for Android (worked in prior Qt)</a>. I got past that, now I have an equally horrible problem.</p>
  
  <p>My Java side QtActivity class calls over to the C++.  That Qt C++ emits a signal.  The slot that should fire is on the main thread (which I've determined is a different thread from what the C++ crossover call executes on).  Well, that never fires.  It's like the main C++ thread is not running.</p>
  
  <p>I wanted to test this further, so I started a QTimer (with a 0 delay) from the construction of an object on the main thread, to make it fire continuously when there are no other events to process.  It executes once, proving that it is connected probably, but then never again.  It's like the C++ main thread just goes to sleep after running once.</p>
  
  <p>I wanted to try maybe running my pertinent C++ in another thread, but that is way too much trouble.  This program has components and class hierarchy which run on numerous platforms.  Everything works but Android (which is again only broken by the new Qt).  I can't risk breaking other platforms.  One of my primary classes is QWidget too, which cannot be moved from the main thread by definition.</p>
  
  <p>Can anyone at least point me to where I can find what source they changed between versions?  It might be in the Qt for Android QtApplication (Java) class perhaps?</p>