// Copyright (C) 2023 The Qt Company Ltd.
// SPDX-License-Identifier: LicenseRef-Qt-Commercial OR GFDL-1.3-no-invariants-only

/*!
    \page deployment-android.html
    \title Deploying an Application on Android
    \brief The technical steps required to deploy a Qt application on Android.
    \nextpage android-openssl-support.html
    \previouspage porting-to-android.html

    This article describes the technical steps required to deploy a Qt
    application to an Android device.

    \section1 Android Packaging Options

    You can package code on Android in three ways: either as an Application
    Package (APK), an Android App Bundle (AAB), or an Android Archive (AAR).
    Each is a specific type of ZIP format that follow a predefined directory
    structure. The differences between these formats are:

    \list
        \li APK files can be deployed and executed on a device.
        \li An AAB is intended to be interpreted by the Google Play store and
        is used to generate APK files for different device architectures and
        form factors.
        \li An AAR fundamentally differs from the APK and AAB formats in that
        it is an Android library. You can use it as a dependency for an Android
        app module, but you cannot run it by itself.
    \endlist

    \section1 Android Application Bundle

    For testing the application locally, the APK format is appropriate,
    as this can be installed and run directly on the device. For distribution
    to the Google Play store, it is recommended to 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 signs them with your publisher key. For more information,
    see \l {Publishing to Google Play}.

    For more information on the AAB format, see the
    \l{Android: App Bundles}{Android App Bundles}.

    In either case, the application bundle is generated from a specific directory
    structure that contains the \c shared libraries of your project and Qt's
    dependencies needed by your application. In addition, any assets, resources,
    \c jar files or project Java code is compiled and included.

    \section2 Generating the Application Bundle

    It is recommended to use \QC to
    \l {\QC: Android Deploy Configuration}{deploy Qt for Android apps}. Otherwise,
    the same can be done through the command line with the help of CMake or qmake.
    For more information, see \l {Building Qt for Android Projects from Command Line}.

    The packaging and deployment process is handled by CMake or qmake which, under
    the hood, use the \l{androiddeployqt} tool to manage the specifics of building
    and deploying an Android app. \QC also uses the same tool.

    \section1 Extending Qt with Android Facilities
    //! To not break \QC link
    \target Android Package Templates

    By default, Qt for Android does most of the heavy lifting to get an Android
    app up and running, having the most useful APIs available directly from Qt,
    or using \l QJniObject to invoke not readily available APIs. The same is
    valid for CMake, which handles the various build and deployment cases. However,
    in some other cases, it might be required to have the full power of native
    Android facilities, such as writing Java/kotlin code or using Android resource
    management. Qt allows that by allowing the user to extend the set of templates.

    The default templates used by Qt are found under the Qt for Android install path,
    for example, under \c {~/Qt/<version>/android_<abi>/src/android/templates} for Unix.
    To use those templates, it's possible to have \QC copy them to your project,
    see \l{\QC: Android Deploy Configuration}. Or you can manually copy them over to
    your project source under a \c android sub-directory. Then make sure to define the
    following property in your \c CMakeLists.txt:

    \badcode
    set_property(TARGET target_name PROPERTY QT_ANDROID_PACKAGE_SOURCE_DIR
              "${CMAKE_CURRENT_SOURCE_DIR}/android")
    \endcode

    Or for qmake in your \c pro file:

    \badcode
    android: ANDROID_PACKAGE_SOURCE_DIR = $$PWD/android
    \endcode

    \note When using \QC, files under this path are by default visible
    under the project files if CMake is used. To achieve the same behavior with
    qmake, add those file paths manually to your project using \l DISTFILES.

    The build process copies the templates to the build directory
    \c {<build_path>/android-build} from your project or from the default
    templates if the project didn't set \c QT_ANDROID_PACKAGE_SOURCE_DIR.
    After that, the directory \c {<build_path>/android-build} acts as the
    packaging directory. The application bundle is created from there using Gradle.

    Now, let's go through the different parts that the user can work with after
    extending the default templates.

    \section2 AndroidManifest.xml

    The \c{AndroidManifest.xml} file gives detailed meta-information about your
    application. This information is used to customize your application bundle,
    and it's used by the device to decide which features to enable, such as the default
    orientation of the application. In addition, it's used by the Google Play Store
    for information on the version code, device support, package name, and lots more.
    The Android Manifest is also used to define \l{Android Services} and custom
    \l{Android: Introduction to Activities}{Android Activities}.

    For more information about the \c AndroidManifest.xml, see
    \l{Qt for Android Manifest File Configuration}{Android Manifest file documentation},
    and {\QC: Android Deploy Configuration}{Editing Manifest Files}.


    \section2 Gradle Files

    \l Gradle is used to build Android packages. Qt includes two sets of Gradle
    related files:

    \list
        \li Gradle wrapper, which is used to download a specific version of Gradle itself,
        and the build scripts that are used to invoke the Gralde build. These files
        come with Qt under for example \c {~/Qt/<version>/android_<abi>/src/3rdparty/gradle}.

        \note Usually, using the same Gradle version that Qt comes with is
        recommended. However, if you wish to use a different Gradle version, you
        can modify the Gradle wrapper \c {gradle-wrapper.properties} and set it
        to the Gradle version you want to use.

        \li The Gradle configuration file \c build.gradle, which is under the
        \l {Extending Qt with Android Facilities}{Android Templates}. This file is
        required by Gradle and can be used to customize the build. It can be used to
        set the build target or minimum API or add library dependencies. It can
        also be used to set the \l {Android: Android Gradle plugin}{Android Gradle plugin},
        which is a required Gradle dependency for building Android apps. An example
        of this is:

        \badcode \AGPVer
        buildscript {
            ...
            dependencies {
                classpath 'com.android.tools.build:gradle:\1'
            }
        }
        \endcode

        For more information, see \l{Android: Build Configuration Files}.
    \endlist

    \section2 Java/Kotlin Code

    To include any Java/Kotlin code to target some APIs that Qt doesn't cover
    or for some other reason, place any code under the path
    \c {<QT_ANDROID_PACKAGE_SOURCE_DIR>/src/}. For example, you can call Java
    methods from within Qt code. For an example, see
    \l{Qt for Android Notifier}{Qt for Android Notifier Example}.

    \section2 Resources

    Android allows the addition of resource files such as icons, images, strings,
    colors, and so on. Those resources can be referenced directly from Java/Kotlin
    code or the manifest file. Any such files can be added to your project under
    \c {<QT_ANDROID_PACKAGE_SOURCE_DIR>/res/}. For example, app icons can be
    added under \c {res/drawable/icon.png}.

    For more information, see \l {Android: App resources overview}.

    \section3 Qt Internal Resources

    By default, Qt packages a few resources that are needed for the apps to run
    properly. For example, on Unix, these resources are found under
    \c {~/Qt/<version>/android_<abi>/src/android/templates/res}.

    \section4 strings.xml

    This file can be found at \c {res/values/strings.xml}.
    This file contains strings the Qt library uses to reference message
    translations for various languages.

    \section4 libs.xml

    This file can be found at \c {res/values/libs.xml}. It is used purely
    to manage deployment information of the Qt libraries, and it's not
    recommended to be manually modified.

    \section2 Android Assets

    For more information on managing Android assets, see
    \l {Porting to Android}{Adding resources}.

    \section2 Android Libraries

    For more information on using third-party libraries with your Qt project,
    see \l {Third-party Android Libraries}{Including a Library to an Android Project}.
*/
