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/****************************************************************************
**
** Copyright (C) 2021 The Qt Company Ltd.
** Contact: https://www.qt.io/licensing/
**
** This file is part of the QtAndroidExtras module of the Qt Toolkit.
**
** $QT_BEGIN_LICENSE:COMM$
**
** Commercial License Usage
** Licensees holding valid commercial Qt licenses may use this file in
** accordance with the commercial license agreement provided with the
** Software or, alternatively, in accordance with the terms contained in
** a written agreement between you and The Qt Company. For licensing terms
** and conditions see https://www.qt.io/terms-conditions. For further
** information use the contact form at https://www.qt.io/contact-us.
**
** $QT_END_LICENSE$
**
**
**
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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}
*/
|
