End to End GUI Development with Qt5

Develop cross-platform applications with modern UIs using the powerful Qt framework

Nicholas Sherriff, Guillaume Lazar, Robin Penea, Marco Piccolino

• Publisher: Packt Publishing
• Year: 2018
• Print ISBN: 9781789531909
• eBook ISBN: 9781789535082
• Edition: 1
• Topic: Informatique
• Subtopic: Applications de bureau

Learn the complete Qt ecosystem and its tools and build UIs for mobile and desktop applications

Key Features

• Unleash the power of the latest Qt 5.9 with C++14
• Easily compile, run, and debug your applications from the powerful Qt Creator IDE
• Build multi-platform projects that target Android, iOS, Windows, MacOS, Linux, and more

Book Description

Qt 5.9 is an application development framework that provides a great user experience and develops full-capability applications with Qt Widgets, QML, and even Qt 3D. This learning path demonstrates the power and flexibility of the Qt framework for desktop application development and shows how you can write an application once and deploy it to multiple operating systems. It will address all the challenges while developing cross-platform applications with the Qt framework.

This course will give you a better understanding of the Qt framework and tools to resolve serious issues such as linking, debugging, and multithreading. It will also upskill you by explaining how to create a to-do-style app and taking you through all the stages in building a successful project. You will build a suite of apps; while developing these apps, you'll deepen your knowledge of Qt Quick's layout systems, and see Qt 3D and widgets in action. The next project will be in the industrial and agricultural sectors: making sense of sensor data via a monitoring system. Your apps should run seamlessly across devices and operating systems such as Android, iOS, Windows, or Mac, and be cost-effective by integrating with existing web technologies. You take the role of lead developer and prototype a monitoring system. In doing so, you'll get to know Qt's Bluetooth and HTTP APIs, as well as the Charts and Web Engine UI modules. These projects will help you gain a holistic view of the Qt framework.

What you will learn

• Install and configure the Qt Framework and Qt Creator IDE
• Implement a rich user interface with QML
• Learn the fundamentals of QtTest and how to integrate unit testing
• Create stunning UIs with Qt Widget and Qt Quick
• Develop powerful, cross-platform applications with the Qt framework
• Design GUIs with Qt Designer and build a library in it for UI previews
• Build a desktop UI with widgets and Designer
• Get familiar with multimedia components to handle visual input and output

Who this book is for

This book will appeal to developers and programmers who would like to build GUI-based applications. Knowledge of C++ is necessary and a basic familiarity with Qt would be helpful.

Persistence

In Chapter 5, Data, we created a framework for capturing and holding data in memory. However, this is only half of the story, as without persisting the data to some external destination, it will be lost as soon as we close the application. In this chapter, we will build on our earlier work and save our data to disk in a SQLite database so that it can live on beyond the lifetime of the application. Once saved, we will also build methods for finding, editing, and deleting our data. To get all these operations for free in our various data models, we will extend our data entities so that they can load and save to our database automatically, without us having to write boilerplate code in each class. We will cover the following topics:

• SQLite
• Primary keys
• Creating clients
• Finding clients
• Editing clients
• Deleting clients

SQLite

General purpose database technology has fragmented in the recent years with the explosion of NoSQL and Graph databases. However, SQL databases are still fighting fit and absolutely an appropriate choice in a lot of applications. Qt comes with built-in support for several SQL database driver types, and can be extended with custom drivers. MySQL and PostgreSQL are very popular open source SQL database engines and are both supported by default, but are intended for use on servers and require administration, which makes them a bit unnecessarily complicated for our purposes. Instead, we will use the much more lightweight SQLite, which is commonly used as a client-side database and is very popular in mobile applications due to its small footprint.

According to the official website at https://www.sqlite.org, "SQLite is a self-contained, high-reliability, embedded, full-featured, public-domain, SQL database engine. SQLite is the most used database engine in the world". Paired with Qt's SQL related classes, it's a snap to create a database and store your data.

The first thing we need to do is add the SQL module to our library project to get access to all of Qt’s SQL goodness. In cm-lib.pro, add the following:

QT += sql

Next, we’ll take onboard what we discussed in the previous chapter and implement our database-related functionality behind an interface. Create a new i-database-controller.h header file in cm-lib/source/controllers:

#ifndef IDATABASECONTROLLER_H #define IDATABASECONTROLLER_H #include <QJsonArray> #include <QJsonObject> #include <QList> #include <QObject> #include <QString> #include <cm-lib_global.h> namespace cm { namespace controllers { class CMLIBSHARED_EXPORT IDatabaseController : public QObject { Q_OBJECT public: IDatabaseController(QObject* parent) : QObject(parent){} virtual ~IDatabaseController(){} virtual bool createRow(const QString& tableName, const QString& id, 
 const QJsonObject& jsonObject) const = 0; virtual bool deleteRow(const QString& tableName, const QString& id) 
 const = 0; virtual QJsonArray find(const QString& tableName, const QString& 
 searchText) const = 0; virtual QJsonObject readRow(const QString& tableName, const 
 QString& id) const = 0; virtual bool updateRow(const QString& tableName, const QString& id, 
 const QJsonObject& jsonObject) const = 0; }; }} #endif

Here, we are implementing the four basic functions of (Create, Read, Update, and Delete) CRUD, which are relevant to persistent storage in general, not just SQL databases. We supplement these functions with an additional find() method that we will use to find an array of matching clients based on supplied search text.

Now, let’s create a concrete implementation of the interface. Create a new DatabaseController class in cm-lib/source/controllers.

database-controller.h:

#ifndef DATABASECONTROLLER_H #define DATABASECONTROLLER_H #include <QObject> #include <QScopedPointer> #include <controllers/i-database-controller.h> #include <cm-lib_global.h> namespace cm { namespace controllers { class CMLIBSHARED_EXPORT DatabaseController : public IDatabaseController { Q_OBJECT public: explicit DatabaseController(QObject* parent = nullptr); ~DatabaseController(); bool createRow(const QString& tableName, const QString& id, const 
 QJsonObject& jsonObject) const override; bool deleteRow(const QString& tableName, const QString& id) const 
 override; QJsonArray find(const QString& tableName, const QString& 
 searchText) const override; QJsonObject readRow(const QString& tableName, const QString& id) 
 const override; bool updateRow(...

Table of contents

• Title Page - Courses
• Copyright and Credits - Courses
• Packt Upsell - Courses
• Preface
• Learn Qt 5
• Hello Qt
• Project Structure
• User Interface
• Style
• Data
• Unit Testing
• Persistence
• Web Requests
• Wrapping Up
• Mastering Qt 5
• Discovering QMake Secrets
• Dividing Your Project and Ruling Your Code
• Conquering the Desktop UI
• Dominating the Mobile UI
• Even Qt Deserves a Slice of Raspberry Pi
• Third-Party Libraries Without a Headache
• Animations - Its Alive, Alive!
• Keeping Your Sanity with Multithreading
• Need IPC? Get Your Minions to Work
• Having Fun with Serialization
• You Shall (Not) Pass with QTest
• All Packed and Ready to Deploy
• Qt Hat Tips and Tricks
• Qt 5 Projects
• Writing Acceptance Tests and Building a Visual Prototype
• Defining a Solid and Testable App Core
• Wiring User Interaction and Delivering the Final App
• Learning About Laying Out Components by Making a Page Layout Tool
• Creating a Scene Composer to Explore 3D Capabilities
• Building an Entity-Aware Text Editor for Writing Dialogue
• Sending Sensor Readings to a Device with a Non-UI App
• Building a Mobile Dashboard to Display Real-Time Sensor Data
• Running a Web Service and an HTML5 Dashboard
• Additional and Upcoming Qt Features
• Bibliography