path: root/doc/src/platforms/android/android-deploying-application.qdoc

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/*!
    \page deployment-android.html

    \title Deploying an Application on Android

    This article gives a technical description of the steps required to take
    any given Qt application and deploy it to an Android device (or market place).

    It is recommended that you use Qt Creator or the Makefile created by qmake to
    create the application bundle. The following information will give you a technical
    insight into the structure of the resulting Android application which is not normally
    required just to write an application.

    All the steps described here are handled automatically by the build script and
    the \l {androiddeployqt}{androiddeployqt deployment tool}, which are run by Qt Creator
    for you.

    \note If you prefer building Android packages from the command line, you may use the "aab"
    or "apk" build targets in the Makefile directly:

    \code
    % make aab
    \endcode

    or

    \code
    % make apk
    \endcode

    \tableofcontents

    \section1 The Application Bundle

    Applications on Android can be packaged in two ways: Either as Application Package (APK)
    or Android App Bundle (AAB). Both are ZIP files which follow a predefined directory
    structure. The difference between the two is that APK files can be downloaded to
    and executed on a device. AAB, on the other hand, is intended to be interpreted by the
    Google Play store and is used to generate APK files.

    For testing the application locally, the APK format is the most appropriate, as this can
    be uploaded directly to the device and run. For distribution to the Google Play store, it is
    recommended that you use AAB instead, which has a similar layout. The added convenience
    of AAB is that you can include all target ABIs in the same bundle without increasing the
    size of the actual package downloaded by your users. When using AAB, the Google Play store
    generates optimized APK packages for the devices issuing the download request and
    automatically sign them with your publisher key.

    Read \l{https://developer.android.com/guide/app-bundle}{the Android documentation} if you
    want to know more about the AAB format.

    In either case, the files must be copied into a special directory structure first, before
    bundling them in a single ZIP file

    This contains one or more binary \c .so files with the code for your application, as
    well as any dependencies, such as Qt's libraries and plugins. In addition, it includes
    \c .jar files containing compiled Java code, assets, resources, and some \c .xml
    files that are used to describe the contents of the bundle.

    \section1 Package Template

    A template for the other sources of an APK package is contained in \c{$QTDIR/src/android/templates}.
    The first step of making a package manually is to copy these files into an empty directory. In this
    guide, we'll refer to this build directory as \c{$BUILD_TARGET}.

    We also need to make sure the application binary is copied into the package. This can be
    achieved by using the following command after running qmake on your application's project file:

    \code
    make install INSTALL_ROOT=$BUILD_TARGET
    \endcode

    It will copy the application binary and any other installation requirements into the packaging
    directory.

    The packaging directory will now consist of the following parts:

    \section2 AndroidManifest.xml

    The \c{AndroidManifest.xml} file gives detailed meta-information about your application. This
    information is used for several things. It is used by the target device to decide which features
    to enable, the default orientation of the application, and so on. In addition, it's used by the
    market place for information on the version code, device support, package name, and lots more.

    For more information about general capabilities of and requirements for the
    \c{AndroidManifest.xml} file, please refer to the
    \l{http://developer.android.com/guide/topics/manifest/manifest-intro.html}{Android documentation on this topic}.

    The default manifest contains some special parameters used by Qt to set up the application for
    running. When you are creating your own Android manifest, you must make sure that it contains these
    parameters. The \c androiddeployqt tool replaces content in the template with the correct
    values.

    \section2 Java Code

    Under \c{$BUILD_TARGET/src} are the files comprising the Java code of the Android application.
    The regular Android application launcher is a Java process, so Qt applications have a
    Java-based entry point. The code in here will load the required Qt libraries, based on the
    meta-information given in other files in the template.

    After loading the libraries, the Java code will call into the application's native \c{main()}
    function on a new thread and the application will launch. At this point, the Java code in
    the template is used to delegate events from Android into Qt.

    One thing to note about the files in this directory is that they can contain code specific
    to certain Android versions. Based on the minimum required Android API level of your
    application it might be necessary to remove some of this code. This is done automatically
    by \c androiddeployqt and Qt Creator during packaging.

    For example, lets say the code contains the following:

    \code
//@ANDROID-21
    @Override
    public void onActivityReenter(int resultCode, Intent data)
    {
        // Do something
        return super.onActivityReenter(resultCode, data);
    }
//@ANDROID-21
    \endcode

    If your minimum Android API level is 20 or lower, the code is removed before
    building, since it's not a supported API on Android API level 20. However, if your minimum API
    level is 21 or higher, it is left in.

    \section2 Resources

    Under the \c{res/} folder in the \c{$BUILD_TARGET} are Android resources that can be accessed
    from the \c{AndroidManifest.xml} and Java code of your application. A typical example of
    resources which should be placed here are the icon files used by the application launcher to
    represent your application.

    In Qt, some translations used for the Ministro service and some files with meta-information
    are in the default resources of the application.

    \section3 res/values/libs.xml

    One of the files containing meta information about the deployment of the application is
    \c{libs.xml}. It consists of the following values:

    \list
    \li \c{qt_sources}: The URL of one or more Ministro repositories that contain the
    necessary Qt libraries. This is used when the Ministro deployment mechanism is active. Read the
    \l{http://necessitas.kde.org/necessitas/ministro.php}{Ministro documentation} for more
    information about such repositories.
    \li \c{bundled_libs}: Libraries in the package's library folder which should be loaded on start-up.
    Library names should be specified without the \c lib prefix and \c{.so} suffix.
    \li \c{qt_libs}: Qt libraries which should be loaded on start-up. When bundled deployment is
    used, these are expected to be found inside the \c{APK}'s library folder. When Ministro
    deployment is in use, they are requested from the Ministro service on the device. And when
    debugging deployment is in use, they are loaded from the \c{/data/local/tmp/qt} directory on the
    target device.
    \endlist

    \section3 res/values/strings.xml

    The \c{strings.xml} file contains some strings used by the \c{AndroidManifest.xml} and by the
    deployment mechanisms, as well as some strings used when loading the Ministro service.

    In particular, the application name and the name of the application binary can be specified
    here. There are also strings that contain additional libraries that should be loaded and
    \c JAR files which should be included in the class path. The latter is only used for deployment
    with Ministro or debug deployment.

    \section2 Libraries

    Under \c libs in the package directory, it's possible to place libraries that should be included
    in the application bundle. \c JAR libraries should be placed directly under \c{libs/}, while
    shared libraries should be put in a subdirectory suitably named after the target ABI
    of the libraries.

    \section1 Building the Android Application Package

    The project can be built using the gradle tool. If an APK intended for release is built, then
    it should be signed and aligned using \c jarsigner and \c zipalign.

    \section1 androiddeployqt

    Building an application package is complex, so Qt comes with a tool which handles the work for
    you. The steps described in this document so far are handled automatically by the tool.

    In addition, there are Makefile build targets for building the package from the
    command line. There is also automated support in Qt Creator for generating both \c APK and \c AAB
    packages.

    \section2 Required Steps Before Running androiddeployqt

    Before running the tool manually, you need to run \c qmake and \c make on your project. Running
    \c qmake creates the \c Makefile, and it will also generate a \c JSON file containing important
    settings used by \c androiddeployqt.

    You should then install the application binary (and any other requirements) into the library
    folder of the \c bundle. If \c{$BUILD_TARGET} is your build directory (the first time you do this,
    the directory should be empty at this point), then you can install the binary with the following
    command:

    \code
    % make install INSTALL_ROOT=$BUILD_TARGET
    \endcode

    \section2 Command Line Arguments

    The only required command line argument when running the tool is \c{--output}. This should
    be set to \c{$BUILD_TARGET}, that is: the build directory where you installed your application
    binary.

    Other command line arguments are optional but useful. Here's a quick overview. More information
    is available by passing the \c{--help} argument to androiddeployqt.

    \list
    \li \c{--aab}: Generate an Android Application Bundle, rather than an APK. Note that this
    invalidates some of the other arguments, such as --install.
    \li \c{--input <file name>}: This allows you to specify the \c JSON file generated by \c qmake.
    By default, \c androiddeployqt will try to guess the file name based on the current working
    directory.
    \li \c{--deployment <mechanism>}: Specify this to pick a different deployment mechanism than the
    default.
    \li \c{--install}: Specify this to install the finished package on the target device or
    emulator. Note that if a previous version of the package is already installed, it will be
    uninstalled first, removing any data it might have stored locally.
    \li \c{--device <ID>}: Specify the ID of the target device or emulator as reported by the \c adb
    tool. If an ID is specified, it will be passed to all calls to \c adb. If it is unspecified, no
    particular device or emulator will be requested by \c adb, causing it to pick a default instead.
    \li \c{--android-platform <platform>}: The SDK platform used for building the Java code of the
    application. By default, the latest available platform is used.
    \li \c{--release}: Specify this to create a release package instead of a debug package. With no
    other arguments, release packages are unsigned and cannot be installed to any device before
    they have been signed by a private key.
    \li \c{--sign <url> <alias>}: Sign the resulting package. Specifying this also implies
    \c{--release}. The URL of the keystore file and the alias of the key have to be specified. In
    addition, there are a number of options that can be specified which are passed through to the
    \c jarsigner tool. Pass \c{--help} to \c androiddeployqt for more information about these.
    \li \c{--jdk <path>}: Specify the path to the Java Development Kit. This is only required for
    signing packages, as it is only used for finding the \c jarsigner tool. If it is unspecified,
    then \c androiddeployqt will attempt to detect \c jarsigner, either using the \c{JAVA_HOME}
    environment variable, or on the \c PATH.
    \li \c{--verbose}: Specify this to output more information about what \c androiddeployqt is
    doing.
    \endlist

    \section1 Dependencies Detection

    Qt comes with a number of plugins which are loaded at run-time when they are needed. These
    can handle anything from connecting to SQL databases to loading specific image formats.
    Detecting plugin dependencies is impossible as the plugins are loaded at run-time, but
    androiddeployqt tries to guess such dependencies based on the Qt dependencies
    of your application. If the plugin has any Qt dependencies which are not also dependencies of
    your application, it will not be included by default. For instance, in order to ensure that
    the SVG image format plugin is included, you will need to add \c{QT += svg} to your \c .pro file
    so that the \l{Qt SVG} module becomes a dependency of your application.

    If you are wondering why a particular plugin is not included automatically, you can run androiddeployqt
    with the \c --verbose option to get the list of missing dependencies for each excluded plugin. You
    can achieve the same in Qt Creator by ticking the \gui{Verbose output} check box in the
    \gui{Deployment configurations}. This is located in the \gui{Run} tab of your \gui{Projects}
    settings.

    It's also possible to manually specify the dependencies of your application. See the documentation
    for the \c{ANDROID_DEPLOYMENT_DEPENDENCIES} qmake variable below.

    \section1 Android-specific qmake Variables

    Unless the project has special requirements such as third party libraries, it should be
    possible to run \c androiddeployqt on it with no modifications and get a working Qt for Android
    application as a result.

    However, there are a set of \c qmake variables that can be used to tailor your package. At some
    point during development, you will most likely want to look into these variables, as they will
    e.g. allow you to set the name of your application as it appears in the application menu on
    devices.

    Here is a list of some variables that are particularly interesting when making Android
    applications:

    \list
    \li \c{ANDROID_DEPLOYMENT_DEPENDENCIES}: By default, \c androiddeployqt will detect the
    dependencies of your application. But since run-time usage of plugins cannot be detected, there
    could be false positives, as your application will depend on any plugins that are \e potential
    dependencies. If you want to minimize the size of your \c APK, it's possible to override the
    automatic detection using the \c{ANDROID_DEPLOYMENT_DEPENDENCIES} variable. This should contain
    a list of all Qt files which need to be included, with paths relative to the Qt install root.
    Note that only the Qt files specified here will be included. Failing to include the correct
    files can result in crashes. It's also important to make sure the files are listed in the
    correct loading order. This variable provides a way to override the automatic detection
    entirely, so if a library is listed before its dependencies, it will fail to load on
    some devices.
    \li \c{ANDROID_PACKAGE_SOURCE_DIR}: This variable can be used to specify a directory where
    additions and modifications can be made to the default Android package template. The
    \c androiddeployqt tool will copy the application template from Qt into the build directory, and
    then it will copy the contents of the \c{ANDROID_PACKAGE_SOURCE_DIR} on top of this, overwriting
    any existing files. The update step where parts of the source files are modified automatically
    to reflect your other settings is then run on the resulting merged package. If you, for
    instance, want to make a custom \c{AndroidManifest.xml} for your application, then place this
    directly into the folder specified in this variable. You can also add custom Java files in
    \c{ANDROID_PACKAGE_SOURCE_DIR/src}.
    \note When adding custom versions of the build files (like strings.xml, libs.xml,
     AndroidManifest.xml, etc.) to your project, make sure you copy them from the package template,
     which is located in \c{$QT/src/android/java}. You should never copy any files from the build
     directory, as these files have been altered to match the current build settings.
    \li \c{ANDROID_EXTRA_LIBS}: A list of external libraries that will be copied into your application's
    library folder and loaded on start-up. This can be used, for instance, to enable OpenSSL
    in your application. Simply set the paths to the required \c{libssl.so} and \c{libcrypto.so}
    libraries here and OpenSSL should be enabled automatically.
    \li \c{ANDROID_EXTRA_PLUGINS}: This variable can be used to specify different resources that your
    project has to bundle but cannot be delivered through the assets system, such as qml plugins. When
    using this variable, \c androiddeployqt will make sure everything is packaged and deployed properly.
    \endlist

    \section1 Deployment in Qt Creator

    Qt Creator will run the \c androiddeployqt tool for you, and provides easy and intuitive user
    interfaces to specify many of the options. For more information, see
    \l{Qt Creator: Deploying Applications to Android Devices}{the Qt Creator documentation}.
*/