Qt allows developers to create cross-platform applications that can run on desktop, web, mobile and embedded devices like Android. There are two main ways to build Qt applications for Android - as a dedicated "boot to Qt" device or as a regular Android application within the Play Store. The talk discusses using Qt Quick for its support of gestures, animations and touch interfaces on mobile. Key Qt features like databases, networking and sensors are supported. Deployment can be to an attached device, simulator or by bundling Qt libraries into a distributable Android application package.

1. Qt on Android
Create a cross-platform
application with Qt

2. 2
• Adrien Leravat
• Embedded Software Engineer
Introduction
• Witekio
• French company, German, USA, Taiwan
• BSP / OS porting to ARM (Linux, Windows, Android,
QNX)
• Embedded software architecture and development
• Mobile expertise (cloud, internet of things)

3. 3
Context
• Creating a new application or service
– Multiple targets and OSes.
• Desktop
• Web
• Mobile and touch devices
– Your smartphones, fridge, …
– Android, iOS, WinRT/WP, Embedded OSes
• Meaning: a lot of time !

4. 4
Qt answer
Your own components
• With Qt 5
– Desktop/Server
• Windows, Linux, Mac
• Smartphones
– Android, iOS, WinRT (preview)
• Embedded devices
– Windows CE, Linux, QNX

5. 5
Qt answer
Your own components
• Why choose Qt for Android
– Build once, runs on multiple targets
• Less development, More maintainable
– No Android knowledge needed
• Big Qt features
– Databases, Threads, Networking, …
• Long living framework, large community
• Each 6 months: New major release !

6. 6
Qt for Android
Your own components
• Two way to build Qt applications with Android
• Boot to Qt: Dedicated device running Android
– Android system without all unnecessary features
(Home, Dalvik, …)
– Make us of Android drivers (accelerometer,
camera,…)
• Qt Android application
– Regular application
– Can be published to Android Play Store
– Can be run on a dedicated Android device

7. 7
Qt for Android
Your own components
• Android versions 2.3.3 (API 10) or later
• Download from free at : http://qt-project.org/downloads
• Qt 5
• Qt Creator
– Unified IDE for developing Qt applications
– Build, deploy and debug
• Qt Creator
– Toolchain for ARMv7 and x86 platforms, Qt
Linguist

8. 8
Installation requirements
• External tools needed
– The Android SDK
• Java Development kit for Android
• The Android NDK
– Native code development kit for Android
• Apache Ant v1.8 or later
– Java code compilation
• JDK v6 or later
– Java development kit

9. 9
Installation requirements
• External tools needed
– The Android SDK
– The Android NDK
– Apache Ant v1.8 or later
– JDK v6 or later
• Integration to Qt Creator
– Tools > Options >Android
– Let’s see !

10. 10
Supported Items
• Qt 5 key features, and more !
– Widgets and Qt Quick graphical user interfaces
– Gestures
– Media player, video input
– Sensors: Accelerometer, Gyroscope, Light sensor,
…
– Databases, threads, networking,…
• Not supported: Webkit

11. Creating a new project

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Project architecture
• New project for Android
– Several projects available: console, native
widgets, Qt Quick graphical application
• Qt Widgets
– No OpenGL hardware acceleration
– Certification needed for your application
– Desktop-only application, leverage all available
widgets
• Qt Quick 2 is preferred, being made
for modern devices
– Gestures, animations
– Design oriented
– Very easy to use

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Project architecture
• New project for Android

14. 14
Project architecture
• Qt Quick project
– Project file configuration .pro
– C++ sources and headers .cpp/.h
– QML and javascript (GUI) .qml/.js

15. 15
Project architecture
• Interface with Android
– Done automatically
– The activity contains the
entry point of the
application
– Load Qt application and
execute native code
– Ministro

16. 16
Project architecture
• AndroidManifest.xml
– Provide meta-information about the app
– Let you change application permissions

17. Polishing with effectsUsing Qt Quick

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Qt Quick Design
• Perfectly fitted for Android
– Gestures, animations
– Network transparent, sensors
• Design oriented
– GUI conception accessible to designers
– Simples components to create your own UI
– Completely separate UI and logic

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Qt Quick Design
• Completely separate UI and logic
– Allows switching UI at runtime
• Access C++ through bindings and functions
– C++ and UI data automatically synchronized
Development
Source code
.cpp/.h
Application
C++ Data
Objects
User interface
.qml .
Scripts
.js
Application
User interface
.qml .
Scripts
.js
Rectangle {
width: height*2; height: 200;
color: “white”
Text {
anchors.fill: parent
text: “Hello world!”
color: “black”
font.pixelSize: 20
}
}

20. 20
Sensors and Gestures
• Sensors and gestures can be entirely managed
from QML
• Great ease of use, no knowledge of Android
needed at all
• Let’s try!
PinchArea {
width:200
height: 200
GridView {
// Some large content
}
}
Pinch / Zoom gesture
Accelerometer {
dataRate: 2
active: true
onReadingChanged{
// Use reading.x/y/z
}
}
Using accelerometer

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Adapting to screen
• Devices come in various resolution and size
• QtQuick2ApplicationViewer::screen()
– Height and width in pixels
– Physical height and width
SmartphoneTablet

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Adapting to screen
• Relative size and position
– Height: parent.height /2
– Limited hard to maintain
• Different QML files
– Very customizable for
each resolutions/size
SmartphoneTabletQt Quick components

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Adapting to screen
• Automatic layouting
– Layout, Row, Grid, …
– Resize and/or move component in allocated space
• Anchors
– Anchors button left
with left the border
– Use anchors to constrain
size
SmartphoneTabletQt Quick components

24. Deployment

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Deployment
• Deploying your application on Android
– Direct deployment to device
• Most convenient for development
• Needs the device to be connected (USB)
– Simulator
– Bundle Qt libraries and files into the apk
• Stand-alone and distributable application package
– Using Ministro
• Minimize the size of the APK

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Deployment
• Ministro
– Available on Google Play
– Application asks Ministro for Qt components
– Ministro download components
• If not installed
• If newer versions exist
– Qt Open Source
• GPLv3+ license for the APK
• BSD License for the API
• Install LGPLv2.1 / GPLV3 Qt libraries

27. 27
Deployment
• Simulator
– Let’s you create and simulate various Android
devices
– Simulate different screen size
– Very convenient for development

28. 28
Deployment
• Finally
– Connect your device
– Hit “Play” !
Embedded device Smartphone
Simulator

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Conclusion
• Qt is a powerful technology, covering more and
more devices and Oses
• Opens new opportunity and ways of doing
software development
• Became an interesting and powerful alternative
to native Android