6. Getting Wired and Managing Downloads | QT5 Blueprints

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QT5 Blueprints

By : Symeon Huang

4 (9)

QT5 Blueprints

4 (9)

By: Symeon Huang

Overview of this book

If you are a programmer looking for a truly cross-platform GUI framework to help you save your time by side-stepping the incompatibility between different platforms and building applications using Qt 5 for multiple targets, then this book is most certainly intended for you. It is assumed that you have a basic programming experience of C++ and fundamental knowledge about Qt.

Preface

Preface

What this book covers

What you need for this book

Who this book is for

Conventions

Reader feedback

Customer support

Free Chapter

1. Creating Your First Qt Application

1. Creating Your First Qt Application

Creating a new project

Changing the layout of widgets

Understanding the mechanism of signals and slots

Connecting two signals

Creating a Qt Quick application

Connecting C++ slots to QML signals

Summary

2. Building a Beautiful Cross-platform Clock

2. Building a Beautiful Cross-platform Clock

Creating a basic digital clock

Tweaking the digital clock

Saving and restoring settings

Building on the Unix platforms

Summary

3. Cooking an RSS Reader with Qt Quick

3. Cooking an RSS Reader with Qt Quick

Understanding model and view

Parsing RSS Feeds by XmlListModel

Tweaking the categories

Utilizing ScrollView

Adding BusyIndicator

Making a frameless window

Debugging QML

Summary

4. Controlling Camera and Taking Photos

4. Controlling Camera and Taking Photos

Accessing the camera in Qt

Controlling the camera

Displaying errors on the status bar

Permanent widgets in the status bar

Utilizing the menu bar

Using QFileDialog

QML camera

Summary

5. Extending Paint Applications with Plugins

5. Extending Paint Applications with Plugins

Drawing via QPainter

Writing static plugins

Writing dynamic plugins

Merging plugins and main program projects

Creating a C++ plugin for QML applications

Summary

6. Getting Wired and Managing Downloads

6. Getting Wired and Managing Downloads

Introducing Qt network programming

Utilizing QNetworkAccessManager

Making use of the progress bar

Writing multithreaded applications

Managing a system network session

Summary

7. Parsing JSON and XML Documents to Use Online APIs

7. Parsing JSON and XML Documents to Use Online APIs

Setting up Qt for Android

Parsing JSON results

Parsing XML results

Building Qt applications for Android

Parsing JSON in QML

Summary

8. Enabling Your Qt Application to Support Other Languages

8. Enabling Your Qt Application to Support Other Languages

Internationalization of Qt applications

Translating Qt Widgets applications

Disambiguating identical texts

Changing languages dynamically

Translating Qt Quick applications

Summary

9. Deploying Applications on Other Devices

9. Deploying Applications on Other Devices

Releasing Qt applications on Windows

Creating an installer

Packaging Qt applications on Linux

Deploying Qt applications on Android

Summary

10. Don't Panic When You Encounter These Issues

10. Don't Panic When You Encounter These Issues

Commonly encountered issues

Debugging Qt applications

Debugging Qt Quick applications

Useful resources

Summary

Index

Index

Making use of the progress bar

An intuitive way to indicate the downloading progress is by using a progress bar. In Qt, it is the QProgressBar class that provides a horizontal or vertical progress bar widget. It uses minimum, value, and maximum to determine the completed percentage. The percentage is calculated by the formula, (value – minimum) / (maximum – minimum). We'll use this useful widget in our example application by performing the following steps:

Go back to the MainWindow class.
Edit the mainwindow.ui file in the Design mode.
Drag Push Button and rename it as newDownloadButton with New Download as its text.
Drag Progress Bar just beneath newDownloadButton.
Change the layout to Lay Out Vertically.
Uncheck textVisible in the progressBar widget's property.

The push button, newDownloadButton, is used to popup DownloadDialog to get a new download task. We need to apply some modifications to mainwindow.h, as suggested here:

#ifndef MAINWINDOW_H
#define MAINWINDOW_H

#include <QMainWindow...

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