QApplication crashes on constructor from JNI (Android)

[Sqrella]

Hi all,

I've created a library that uses Qt Widgets; if called from non-Qt application, it creates an instance of QApplication.
Everything works fine on Windows and linux, from C app and also from a Java app (using JNA).
It works also in Android if called from a Qt app.
Now I'm trying to get it to work on Android calling it from a Java application made with Android Studio, using JNI.
At first I had a problem finding the platform plugin, but solved setting the QT_QPA_PLATFORM_PLUGIN_PATH.
But when I create QApplication object, it crashes on constructor, with SIGSEGV in libc.
I don't think that is a problem with argc and argv parameters, because If I create a QCoreApplication instead it doesn't crash, but I need widgets...
I am using Qt 5.6.2, but tried also 5.8 and 5.9.1, same result.
And NDK r10e, but also with r14b is the same.

In the Android Studio project, in the folder jniLibs\armeabi-v7a, I've put the following libs together with mine:

libgnustl_shared.so
libplugins_platforms_android_libqtforandroid.so
libQt5AndroidExtras.so
libQt5Core.so
libQt5Gui.so
libQt5Multimedia.so
libQt5Network.so
libQt5Widgets.so

I have copied them from the APK that the working Qt app generates...

Have you any suggestions?
Thanks

[SGaist]

Hi,

Can you share the stack trace ?

[Sqrella]

Hi,

sorry, I'm completely new to Android Studio...
In the logcat I see only this line:
08-07 08:51:41.810 17576-17576/com.example.gb.myndkapplication2 A/libc: Fatal signal 11 (SIGSEGV), code 1, fault addr 0x0 in tid 17576 (ndkapplication2)

Do you mean this?

Thanks

[SGaist]

Based on this thread, it seems that other people had some success using Qt classes from an Android application.

However, I don't know whether the GUI part can be used that way. I think you should check the Qt Android mailing list to find out whether it's currently supported. You'll find there Qt's Android port developers/maintainers. This forum is more user oriented.

[Greg Perez]

Hi @Sqrella . Were you able to track down the issue? I am experience the same crash in QT 5.9 and I'm unable figure out the root problem.

[ambershark]

@Greg-Perez Well based on his error findClass is returning a nullptr and then it is being referenced causing a crash.

So whatever findClass is trying to find, it isn't. But nobody checks the return and assumes it was successful and tries to use it.