Virtual keyboard problem in Android app

I've ported an app from desktop to Android. After working around some issues with swprintf / swscanf in the library I was using, the app builds without error on Windoze and my Samsung Galaxy Tab 10.2 tablet (running Android 4.2 Jelly Bean). At run time, though the behavior is different.

I am having an issue with QLineEdit and the virtual keyboard on the tablet. When I tap on the line edit, the virtual keyboard appears. When I start typing, it shows that I am editing / adding / inserting characters into what is already in the line edit. But when I press the "Done" (return) key on the virtual keyboard, it takes everything I have typed and appends it to whatever was already there. In effect, I get a duplicate - the existing content plus whatever I type. On the Samsung, there seems to be some autocomplete thing that pops up above the keyboard that wants to interfere with what you're typing. I don't know how to disable / kill that, and I suspect it is that "feature" which is causing my problem.

The same app running in Windoze behaves as one would expect - whatever you type replaces / edits what was there to begin with, and when you hit return, you get what you intended.

Is there something I need to do in my app to fix this or (if anyone knows) is this some issue with the virtual keyboard on the Samsung (or Android 4.2)?

I haven't been able to create a virtual Android device (or at least one that runs) on my PC, so I can't test this except by debugging on the tablet itself.