Qt + Necessitas + Android-拖放防止显示重新绘制

Question

The current ALPHA 4 version of Necessitas (Qt port for Android) has a bug with drag and drop. The drag in drop works fine except it blocks the event loop preventing the GUI getting re-paint events. I reported the problem in the project bug tracker. https://bugs.kde.org/show_bug.cgi?id=304180

This will probably be solved in the next release and does not seem to be a showstopper to the developers of the port which makes sens as Necessitas is still Beta. I wanted to give it a trial because what I am porting requires this to work.

I need some help from Qt guru who is familiar with event loop and Qt internal. I know from the Qt doc that the drag and drop implementation is platform dependent, you can read the following note,

Note: On Linux and Mac OS X, the drag and drop operation can take some time, but this function does not block the event loop. Other events are still delivered to the application while the operation is performed. On Windows, the Qt event loop is blocked while during the operation.

Looking inside the Qt source, I ended at QDropManager which is implemented in

src/gui/kernel/qdnd_XXX.cpp

This file has different implementation for X11, Win, MacOS and Symbian. In the Necessitas Qt its X11 version is used for the build.

Any directions on how to fix this issue will be very helpful.

Answer 1

You can just repaint all necessary widgets by yourself. For example call repaint() function at dragMoveEvent. dragMoveEvents are generating successfully. It works for me on android.

Also, you can try to create special thread for QDrag object. As far as I know, QThreads have their own event loops. But I haven't tried this yet.