What is the proper way to deploy C ++ QML plugins on a mobile device?

Question

I played a lot with the Box2D QML plugin and everything looks very good. However, I wanted to deploy my sample application on Android (SGS2), but I cannot get it to work. I try to run it on an AVD or on a device, this will not work. androiddeployqt succeeds, but then I get “Unable to launch MyApp” and no other information about why it couldn’t start. I can successfully run qml applications on AVD and device, but this has something to do with the plugin, and I can not find any links to solve it.

I tried to configure DEPLOYMENTFOLDERS differently, but if I am wrong, then all this fails. Even when I do not receive the error message, in this case I assume that everything is correct, it still does not start.

I have been struggling with this a bit for some time and cannot find any useful information to solve it. If you know of a project that uses the C ++ plugin and can be successfully deployed on an Android device, this is also good.

I am using Qt 5.2.0 compiled for android and the qt5 branch box2d

Answer 1

We were getting “module not found” errors while we tried to get our QML module to work in the Android Qt application. With Qt 5.3, we were able to get a QML plugin that is recognized only by deploying the plugin in the QT_INSTALL_QML directory, where the official Qt Qt modules are located. In our case, this is the directory / opt / Qt / 5.3 / android_armv7 / qml.

Plugin side

Our .pro file for the plugin looks like this:

 TEMPLATE = lib TARGET = prova QT += qml quick multimedia CONFIG += qt plugin c++11 console CONFIG -= android_install TARGET = $$qtLibraryTarget($$TARGET) uri = com.mycompany.qmlcomponents # Input SOURCES += \ src1.cpp \ src2.cpp HEADERS += \ src1.h \ src2.h ##The below is generated automatically by Qt Creator when you create a new "Qt Quick 2 Extension Plugin" project for Android #Copies the qmldir file to the build directory !equals(_PRO_FILE_PWD_, $$OUT_PWD) { copy_qmldir.target = $$OUT_PWD/qmldir copy_qmldir.depends = $$_PRO_FILE_PWD_/qmldir copy_qmldir.commands = $(COPY_FILE) \"$$replace(copy_qmldir.depends, /, $$QMAKE_DIR_SEP)\" \"$$replace(copy_qmldir.target, /, $$QMAKE_DIR_SEP)\" QMAKE_EXTRA_TARGETS += copy_qmldir PRE_TARGETDEPS += $$copy_qmldir.target } #Copies the qmldir file and the built plugin .so to the QT_INSTALL_QML directory qmldir.files = qmldir unix { installPath = $$[QT_INSTALL_QML]/$$replace(uri, \\., /) qmldir.path = $$installPath target.path = $$installPath INSTALLS += target qmldir } 

Our qmldir (in the root root of the plugin source):

 module com.mycompany.qmlcomponents plugin prova 

Application side

The .pro file looks like this:

 TEMPLATE = app QT += qml quick widgets multimedia CONFIG+= console SOURCES += main.cpp RESOURCES += qml.qrc # Additional import path used to resolve QML modules in Qt Creator code model QML_IMPORT_PATH = # Default rules for deployment. include(deployment.pri) contains(ANDROID_TARGET_ARCH,armeabi-v7a) { ANDROID_EXTRA_LIBS = \ /opt/Qt/5.3/android_armv7/qml/com/mycompany/qmlcomponents/libprova.so } 

Important Note. Any library that your qml plugin uses must also be specified in ANDROID_EXTRA_LIBS in order to be embedded in apk. This includes the Qt components, and listing them in QT + = is not enough unless you use them in your application.

We really do not know if the inclusion of additional libprova.so is necessary. Most likely no.

main.cpp looks like this:

 #include <QApplication> #include <QQmlApplicationEngine> int main(int argc, char *argv[]){ QApplication app(argc, argv); QQmlApplicationEngine engine; engine.load(QUrl(QStringLiteral("qrc:///main.qml"))); return app.exec(); } 

main.qml includes only the plugin:

 import QtQuick 2.2 import QtQuick.Controls 1.1 import QtMultimedia 5.0 import com.mycompany.qmlcomponents 1.0 ... 

Build and Deploy

The way to build and deploy the plugin is qmake (from the android-armv7 toolchain from Qt), then make install . It installs the qmldir file and plugin. Also in the QT_INSTALL_QML directory.

How we create and deploy a project that uses the plugin is qmake (again, from the android-armv7 Qt toolchain), then make install INSTALL_ROOT=. (set to build the directory), then run androiddeployqt . The last command creates the structure of the Android project using qmldirs in assets and libraries in libs / and binds all this in apk via ant . See http://qt-project.org/wiki/Android for more on this procedure.

In short, we were able to get our QML plugin as part of the Android project by placing it in a private Qt qml directory. Hope this helps in some way.