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Part-1: Install and Configure Qt5 on Ubuntu 16.04

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Series

Tutorial

  • qt: 5.7.0
  • qmake: 3.0 based on Qt 5.7.0
  • qtcreator: 3.5.1 based on Qt 5.5.1

purge existing qt

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sudo apt-get purge qt5-default qtcreator 
sudo apt-get purge qt4-designer qt4-dev-tools

install qt57

In addition, building graphical Qt applications requires OpenGL libraries and headers installed. On Ubuntu and other Debian-based Linux systems you can get OpenGL and the minimal set of development tools by installing the packages libgl1-mesa-dev and build-essential, i.e. by running this command:

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sudo apt-get install build-essential libgl1-mesa-dev

Download qt and install.

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sudo apt-get install build-essential libgl1-mesa-dev
wget http://download.qt.io/official_releases/qt/5.7/5.7.0/qt-opensource-linux-x64-5.7.0.run
chmod +x qt-opensource-linux-x64-5.7.0.run
./qt-opensource-linux-x64-5.7.0.run

install to /opt/Qt5.7.0

create links to /opt/qt/

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cd /opt
sudo ln -s /opt/Qt5.7.0 qt

qtchooser

add qt57.conf

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cat /usr/share/qtchooser/qt57.conf 

/opt/qt/5.7/gcc_64/bin
/opt/qt/5.7/gcc_64/lib

# link to qt57
cd /usr/lib/x86_64-linux-gnu/qtchooser
sudo ln -s /usr/share/qtchooser/qt57.conf qt57.conf
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cd /usr/lib/x86_64-linux-gnu/qt-default/qtchooser

sudo rm default.conf
sudo ln -s /usr/share/qtchooser/qt57.conf default.conf
ls -l default.conf
default.conf -> /usr/share/qtchooser/qt57.conf

qt conf

/usr/share/qtchooser/

  • qt4-x86_64-linux-gnu.conf (FILE)
  • qt5-x86_64-linux-gnu.conf (FILE)
  • qt57.conf (FILE)

/usr/lib/x86_64-linux-gnu/qtchooser/

  • 4.conf (link)
  • 5.conf (link)
  • qt4.conf (link)
  • qt5.conf (link)
  • qt57.conf (link)

/usr/lib/x86_64-linux-gnu/qt-default/qtchooser/

  • default.conf (link) qt57.conf

qtchooser

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which qtchooser 
/usr/bin/qtchooser

qtchooser -l

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default
qt4-x86_64-linux-gnu
qt4
qt5-x86_64-linux-gnu
qt5

qtchooser env

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qtchooser -print-env
QT_SELECT="default"
QTTOOLDIR="/opt/qt/5.7/gcc_64/bin"
QTLIBDIR="/opt/qt/5.7/gcc_64/lib"

export QT_QPA_PLATFORM_PLUGIN_PATH

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vim .bashrc
export QT_QPA_PLATFORM_PLUGIN_PATH=/opt/qt/5.7/gcc_64/plugins/platforms

otherwise,errors may occur. Failed to load platform plugin "xcb".

QtCreator Tutorial

install qtcreator

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sudo apt-get -y install qtcreator

qtcreator -version
Qt Creator 3.5.1 based on Qt 5.5.1

create application

  1. Start qtcreator and create a Qt Widget Application named hello.

  2. Add a resource file named resource.qrc.

     hello-->right click--> Add New... --->qt---> qt resource file---> name resource---> generate resource.qrc

  3. and then import images to resource.qrc

     Resources | resource.qrt--->right click---> Add Prefix...---> name /prefix
 Resources | resource.qrt | /prefix--->right click ---> Add Existing Files... ---> choose images ---> OK

  4. use resource in mainwindow.ui

     button ---> property page ---> icon ---> Choose Resource... ---> select image ---> OK

qt slots

method 1

steps: 

mainwindow.ui ---> choose button ---> right click ---> Go to slot... ---> choose clicked() ---> OK

will add slots in mainwindow.h automatically

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private slots:
    void on_pushButtonOK_clicked();

and in mainwindow.cpp

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void MainWindow::on_pushButtonOK_clicked()
{
    
}

Tips: if we use on_pushButtonOK_clicked style, there is no need to connect with slots in MainWindow constructor by hand.

method 2 (OK)

add slots in mainwindow.h by hand

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private slots:
    void pushButtonCancel_clicked();

and in mainwindow.cpp

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void MainWindow::pushButtonCancel_clicked()
{
    
}

connect button with slot in mainwindow.cpp

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MainWindow::MainWindow(QWidget *parent) :
    QMainWindow(parent),
    ui(new Ui::MainWindow)
{
    ui->setupUi(this);

    // connect
    connect(ui->pushButtonCancel, SIGNAL(clicked()), this, SLOT(pushButtonCancel_clicked()));
}

Code Example

folder

folder structure like this:

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$ tree hello/

hello/
├── CMakeLists.txt
├── hello.pro
├── hello.pro.user
├── images
│   ├── kezunlin_logo.png
│   ├── logo.svg
│   └── searchicon.png
├── main.cpp
├── mainwindow.cpp
├── mainwindow.h
├── mainwindow.ui
└── resource.qrc

1 directory, 11 files

code

mainwinow.h

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#ifndef MAINWINDOW_H
#define MAINWINDOW_H

#include <QMainWindow>

namespace Ui {
class MainWindow;
}

class MainWindow : public QMainWindow
{
    Q_OBJECT

public:
    explicit MainWindow(QWidget *parent = 0);
    ~MainWindow();

private slots:
    void on_pushButtonOK_clicked(); // method1
    void pushButtonCancel_clicked(); // method2

private:
    Ui::MainWindow *ui;
};

#endif // MAINWINDOW_H

mainwindow.cpp

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#include "mainwindow.h"
#include "ui_mainwindow.h"

#include <QMessageBox>

MainWindow::MainWindow(QWidget *parent) :
    QMainWindow(parent),
    ui(new Ui::MainWindow)
{
    ui->setupUi(this);

    // connect
    connect(ui->pushButtonCancel, SIGNAL(clicked()), this, SLOT(pushButtonCancel_clicked()));
}

MainWindow::~MainWindow()
{
    delete ui;
}

void MainWindow::on_pushButtonOK_clicked()
{
    QString text = ui->lineEditName->text();
    QMessageBox::information(this, "OK", text);
    ui->pushButtonOK->setText( tr("(OK. click me)") );
}

void MainWindow::pushButtonCancel_clicked()
{
    QString text = ui->lineEditName->text();
    QMessageBox::information(this, "Cancel", text);
    ui->pushButtonCancel->setText( tr("(Cancel.click me)") );
}

main.cpp

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#include "mainwindow.h"
#include <QApplication>

int main(int argc, char *argv[])
{
    QApplication a(argc, argv);
    MainWindow w;
    w.show();

    return a.exec();
}

CMakeLists.txt

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cmake_minimum_required(VERSION 2.8.8)

project(helloworld)

# Find includes in corresponding build directories
set(CMAKE_INCLUDE_CURRENT_DIR ON)
# Instruct CMake to run moc automatically when needed.
set(CMAKE_AUTOMOC ON)

# ${QT_INCLUDE_DIRS} ${QT_LIBRARIES} and so on are all Qt4 Macro Definitions!!!!!
# Find the QtWidgets library
find_package(Qt5Core)
find_package(Qt5Widgets)
find_package(Qt5Gui)
find_package(Qt5OpenGL)
find_package(Qt5Xml)

#message( [qt] ${Qt5Core_INCLUDE_DIRS} )
#message( [qt] ${Qt5Core_LIBRARIES} )
#message( [qt] ${Qt5Widgets_INCLUDE_DIRS} )
#message( [qt] ${Qt5Widgets_LIBRARIES} )

# cpp files
aux_source_directory(. SRC_LIST)

# ui files
qt5_wrap_ui(ui_FILES mainwindow.ui)
# resource files
qt5_add_resources(qrc_FILES resource.qrc)

message( [Main] ${SRC_LIST} ) # ./main.cpp./mainwindow.cpp
message( [Main] ${ui_FILES} ) # build/ui_mainwindow.h
message( [Main] ${qrc_FILES} )# build/qrc_resource.cpp

# Tell CMake to create the helloworld executable
add_executable(${PROJECT_NAME} ${SRC_LIST} ${ui_FILES} ${qrc_FILES})

qt5_use_modules(${PROJECT_NAME} Core Widgets OpenGL Xml Gui)

# Use the Widgets module from Qt 5.
#qt5_use_modules(helloworld Widgets)

# link other libraries
#target_link_libraries (${PROJECT_NAME} ${SPEC_OPENCV_LIBS})

CMakeLists.txt 2

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cmake_minimum_required(VERSION 3.0)

set(PROJECT_NAME demo)

set(CMAKE_BINARY_DIR ${CMAKE_SOURCE_DIR}/bin)  # bin/

set(EXECUTABLE_OUTPUT_PATH ${CMAKE_BINARY_DIR})
set(LIBRARY_OUTPUT_PATH ${CMAKE_BINARY_DIR})

set(CMAKE_CXX_STANDARD 11)
#set(CMAKE_PREFIX_PATH ${QTDIR})
set(CMAKE_AUTOMOC ON)
set(CMAKE_AUTOUIC ON)
set(CMAKE_AUTORCC ON)

# QT5_DIR /opt/Qt5.7.0/5.7/gcc_64/lib/cmake/Qt5
find_package(Qt5 REQUIRED Widgets Core Gui Network OpenGL)
find_package(OpenCV REQUIRED COMPONENTS core highgui imgproc features2d calib3d )
find_package(Protobuf REQUIRED) # 3.6.1
find_package(VTK REQUIRED) # 8.1.2
include(${VTK_USE_FILE})

MESSAGE( [Main] " VTK_INCLUDE_DIRS = ${VTK_INCLUDE_DIRS}")
MESSAGE( [Main] " VTK_LIBRARIES = ${VTK_LIBRARIES}")

find_package(PCL REQUIRED) # 1.9.1
#find_package(PCL REQUIRED COMPONENTS common io filters visualization)

link_directories(${PCL_LIBRARY_DIRS})
add_definitions(${PCL_DEFINITIONS})

message ([main] "PCL_DIR = ${PCL_DIR}")
message ([main] "PCL_FOUND = ${PCL_FOUND}")
message ([main] "PCL_INCLUDE_DIRS = ${PCL_INCLUDE_DIRS}")
message ([main] "PCL_LIBRARIES = ${PCL_LIBRARIES}")

message ([main] "PCL_LIBRARY_DIRS = ${PCL_LIBRARY_DIRS}")
message ([main] "PCL_COMMON_LIBRARIES = ${PCL_COMMON_LIBRARIES}")
message ([main] "PCL_IO_LIBRARIES = ${PCL_IO_LIBRARIES}")
message ([main] "PCL_FILTERS_LIBRARIES = ${PCL_FILTERS_LIBRARIES}")
message ([main] "PCL_VISUALIZATION_LIBRARIES = ${PCL_VISUALIZATION_LIBRARIES}")

include_directories(
	./ # current folder

#	${GFLAGS_INCLUDE_DIRS}
#	${GLOG_INCLUDE_DIRS}
#	${GTEST_INCLUDE_DIRS}
	${PROTOBUF_INCLUDE_DIRS}
	${Boost_INCLUDE_DIRS} 
	${OpenCV_INCLUDE_DIRS}
	${VTK_INCLUDE_DIRS}
	${PCL_INCLUDE_DIRS}
) 

set(SOURCE_FILES
    main.cpp
    MainWindow.cpp
    ./proto/camera_image.pb.cc
    ./proto/point_cloud.pb.cc
)

set(RESOURCE_FILE resource.qrc)

add_executable(${PROJECT_NAME} ${SOURCE_FILES} ${RESOURCE_FILE})

target_link_libraries(${PROJECT_NAME} 
    Qt5::Widgets Qt5::Gui Qt5::Core Qt5::OpenGL Qt5::Network
	${Boost_LIBRARIES}
	${PROTOBUF_LIBRARIES}
	${OpenCV_LIBRARIES}
	${VTK_LIBRARIES}
	${PCL_LIBRARIES}    
    pthread
    rt
)

cmake

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cd hello
mkdir build
cd build
cmake ..
make

run

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./helloworld

screen snapshot like this:

qt demo window

Reference

History

  • 20180108: created.