qt-everywhere-src-5.15.1/qtandroidextras/examples/androidextras/services/servicebinder/doc/src/qtandroidextras-example-service-binder.qdoc

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/*!
    \title Android Service with QAndroidBinder
    \ingroup examples-qtandroidextras
    \example services/servicebinder
    \brief Demonstrates how to run an Android service in a separate process,
           and how to communicate between the service process and the main process
           using QAndroidBinder.

    \image androidservices.png

    This example demonstrates how to create and run an Android service in
    a separate process and using a separate \c .so lib file, and then exchange
    data between the two processes using \l{QAndroidBinder}.

    When clicking the \uicontrol {Send to Service} button, the name entered in the QML
    view, Qt, in this case, is sent to the Android service. Then, the service
    replies back with the message \c {Hello Qt} which is printed in the QML view.

    \include examples-run.qdocinc

    \section1 Create the Service

    To start a service in its own process, extend the \c QtService class for
    your service. Extending \c QtService allows the service to load the necessary
    Qt libraries used for Qt.

    Start by creating the Java service class. The following class extends \c QtService
    and acts as your service entry point:

    \quotefromfile services/servicebinder/android/src/org/qtproject/example/qtandroidservice/QtAndroidService.java
    \skipto package
    \printuntil /^\}/

    This class can have any logic you want using Java code. However, you don't need
    any logic to communicate with Qt as that will be done using \l{QAndroidBinder}.

    \section1 Manage the AndroidManifest.xml File

    To use the service, it must be declared in the \c AndroidManifest.xml
    file as follows:

    \quotefromfile services/servicebinder/android/AndroidManifest.xml
    \skipto <service
    \printuntil </service>

    The important part of this service declaration is the \c lib_name part.
    It will ensure that the service is run by the service's own lib file:

    \quotefromfile services/servicebinder/android/AndroidManifest.xml
    \skipto android:value="service"
    \printuntil android:value="service"

    \section1 Handle the Service Start

    Create a sub-project for the service, as follows:

    \quotefromfile services/servicebinder/service.pro
    \printuntil androidbinder.cpp

    In \c androidbinder.cpp, implement a class that inherits \l{QAndroidBinder}.
    This is the binder that the main application will use to connect to the service
    by binding to it. \l{QAndroidBinder::onTransact()} uses a \c code integer to
    differentiate between actions. Use a \c switch case or \c if conditions to
    handle all expected actions that the binder could expect:

    \quotefromfile services/servicebinder/androidbinder.cpp
    \skipto onTransact
    \printuntil /^\}/

    In the service's \c main(), start the \l{QAndroidBinder} along with
    \l{QAndroidService}:

    \quotefromfile services/servicebinder/service_main.cpp
    \skipto main
    \printuntil /^\}/


    \section1 Handle the Application Start

    In the main application side, a \l{QAndroidServiceConnection} implementation
    is required to bind to the service and exchange data with it. Implement
    the functions \l{QAndroidServiceConnection::onServiceConnected()} and
    \l{QAndroidServiceConnection::onServiceDisconnected()}:

    \quotefromfile services/servicebinder/qtandroidservice.cpp
    \skipto onServiceConnected
    \printuntil }
    \printuntil }

    Then, create a function to explicitly send messages to the service:

    \quotefromfile services/servicebinder/qtandroidservice.cpp
    \skipto sendToService
    \printuntil }

    Once you have all that ready, it's time to start the service and bind to it
    as follows:

    \quotefromfile services/servicebinder/qtandroidservice.cpp
    \skipto :QtAndroidService
    \printuntil }

    The \l{QtAndroid::bindService()} is called using \l{QtAndroid::AutoCreate}
    which starts the service if it's not already running.

    \note To receive data explicitly sent from the service (i.e. not just a reply),
        implement \l{QAndroidBinder} in the main application the same way
        it's done on the service. Once you have that, the service could initially
        send a message.

    Then, create an instance for the custom \l{QAndroidServiceConnection} class
    and connect it to QML. Add the following in \c main.cpp:

    \quotefromfile services/servicebinder/main.cpp
    \skipto QtAndroidService
    \printuntil setContextProperty

    Then, add a \l Connections element to watch for the incoming messages from
    the service in \c main.qml:

    \quotefromfile services/common/main.qml
    \skipto Connections
    \printuntil /^\ {4}\}/

    And set the \c onClicked for the sending button to:

    \quotefromfile services/common/main.qml
    \skipto onClicked
    \printline onClicked

    \sa {Android Services}, {Qt for Android}, {Qt Android Extras}
*/