QT GUI programming!

1, QT basis

1.1 introduction to QT

1.1.1. What is QT

A bunch of C++/python class libraries (GUI classes, network,...)
Free open source

1.1.2 QT characteristics:

Excellent cross platform characteristics:
Qt supports the following operating systems: Windows, Linux, Solaris, sun0s, FreebSD, BSD/S, SCO, AIX, 0S390, QNX, android, etc
object-oriented
-Qt's good encapsulation mechanism makes Qt very modular and reusable
Rich API
Qt includes up to 500 + C S++
A large number of development documents
Network/XML/Open GL/Database/webkit/

1.2 QT application scope

KDE
ava
Google earth
0pera browser
Skype Internet phone
QCad
Adobe Photoshop Album
CGAL computational geometry Library
...

1.3 development environment

Visualization tools: Qt Designer, Qt Assistant Qt Linguist, Qt Creator
Command line program: update, release, qmake, uic, moc
Qt SDK development kit
Qvfd

1.4 QT software download and installation tutorial

1.4.1 QT software download

Official download address of QT version: http://download.qt.io/archive/qt/
Baidu cloud disk sharing download link: https://pan.baidu.com/s/1T-csDlc0B_C4EY7BYP-3mA Extraction code: zllk

1.4.2 QT software installation

To install the Linux Windows version, refer to the link: https://blog.csdn.net/qq_23473839/article/details/80523318

-The detailed windows version installation tutorial is as follows:

QT software installation completed!

1.5 QT memory management

1.5.1. When new and delete are used, memory is allocated in the heap.
Heap memory space must be completely freed by delete to prevent memory leakage. Objects allocated on the heap can survive as long as they are not deleted.
The stack is automatically allocated and managed by the system. Local variables come from the stack area. As long as the stack area exceeds the scope, the data will be automatically recycled.

1.6. First QT procedure

1.6.1 create project

Three basic templates (QWidget/ QDialog/ QMainWindow)

Refer to the following links for the differences between the three basic templates: https://www.pianshen.com/article/20181654761/

Project creation completed!
1.6.2 first procedure

#Include < QPushButton > / / call the button header file

/*Select combination*/
QPushButton *bt;      	//Construct a pointer here

Refer to the RGB color comparison table: https://bj.96weixin.com/tools/rgb

this->setFixedSize(640, 480);           //Setup page
bt = new QPushButton("Sign in", this);     //Construct a button object
bt->setGeometry(300, 400, 100, 50);    //Set button coordinates
//bt->setStyleSheet("QPushButton{color:blue;};");               // Setting style; Set font color blue
//bt->setStyleSheet("QPushButton{background-color:blue;};");    // Setting style; Set the login box background to display blue
bt->setStyleSheet("QPushButton{background-color:#63B8FF;}; "); / / set style; set login. You can set the color blue according to the color code table

First program example code link:
Is the untitled1 folder: https://pan.baidu.com/s/1_sonChu0NyJhtJkmEsRSKQ
Extraction code: u4uy

1.7 print tracking

1.8 example of QT project

1.8.1. Basic template (QWidget/QDialog/QMainWindow)
1.8.2 process Declare the elements on the interface; 2. Construct the required controls; 3. Typesetting; 4. Front and rear hanging
1.8.3 details:
(1) Typesetting

Vertical QVBoxLayout
Horizontal QHBoxLayout
Grid (2D array) QGridLayout

(2) Signal and slot

public slots: declare slot functions
Connect (signal sending object, signal receiving object, slot function);

Programming example 1:
display a dialog box

#Include < QPushButton > / / call the button header file
#Include < qlineedit > / / line editor

/*Select combination*/
QPushButton *bt;    //Construct a pointer here
QLineEdit *le;      //Line editor

#include "QVBoxLayout" / / vertical class of typesetting

//1. Really apply for objects in the stacking area
bt = new QPushButton("Sign in", this);      //Construct a button object
le = new QLineEdit;                     //Construct a dialog box

//2. Make necessary typesetting
QVBoxLayout *vbox = new QVBoxLayout;    //Vertical layout
vbox->addWidget(le);                    //Row edit box
vbox->addWidget(bt);                    //Button
this->setLayout(vbox);                  //Display the current main interface

Programming example 1-2 code link:
In the untitled2 folder: https://pan.baidu.com/s/1_sonChu0NyJhtJkmEsRSKQ
Extraction code: u4uy

Programming example 2:
Read: click the button and the computer will broadcast voice automatically

#Include < QPushButton > / / call the button header file
#Include < qlineedit > / / line editor
#Include < qdebug > / / print trace
#Include < qtexttospeech > / / speaking class; You need to add a language conversion class in pro: texttospeech

/*read*/
public slots: //Declare this function as a slot function (which can be excited by a signal); QT c + + syntax
void xxx()
{
    x->say("Hello");                //Speaking class, language output Hello
    qDebug() << "xxxxxxxxxxxx";     //Display and print XXXXXXXXXXX
}

/*Select combination*/
QPushButton *bt;    //Construct a pointer here
QLineEdit *le;      //Line editor

QTextToSpeech *x;   //Talking class

QT       += core gui texttospeech

#include "QVBoxLayout" / / vertical class of typesetting

//1. Really apply for objects in the stacking area
bt = new QPushButton("read", this);      //Construct a button object
le = new QLineEdit;                     //Construct a dialog box

 x = new QTextToSpeech;                  //Construct a speaking class

//2. Make necessary typesetting
QVBoxLayout *vbox = new QVBoxLayout;    //Vertical layout
vbox->addWidget(le);                    //Row edit box
vbox->addWidget(bt);                    //Button
this->setLayout(vbox);                  //Display the current main interface

//3. Front and rear console hooking (connecting signal and cable)
connect(bt, SIGNAL(clicked(bool)), this, SLOT(xxx()));      //Signal of button connection; If the button is pressed, xxx below should click execute

x->say(le->text());             //Speaking class, edit the text in the box

Programming example 1-2 code link:
In the untitled2 folder: https://pan.baidu.com/s/1_sonChu0NyJhtJkmEsRSKQ
Extraction code: u4uy

Programming example 3:
Horizontal layout | grid layout

#Include < qhboxlayout > / / layout horizontal layout

QHBoxLayout *hbox = new QHBoxLayout;     //Horizontal layout
hbox->addWidget(le);                     //Row edit box
hbox->addWidget(bt);                     //Button
this->setLayout(hbox);                   //Display the current main interface

#Include < qgridlayout > / / typesetting grid layout

QGridLayout *gbox = new QGridLayout;      //Grid layout
gbox->addWidget(le, 0, 0, 1, 2);          //Row edit box
gbox->addWidget(bt, 1, 1, 1, 1);          //Button
setLayout(gbox);

Programming example 3 code link:
In the untitled3 folder: https://pan.baidu.com/s/1_sonChu0NyJhtJkmEsRSKQ
Extraction code: u4uy

Programming display: multiple button control

//Extract the signaled object
QPushButton *xbt = static_cast<QPushButton *>(sender());
qDebug()<<xbt->text();

Programming example: multiple button control links:
In the untitled3 folder: https://pan.baidu.com/s/1_sonChu0NyJhtJkmEsRSKQ
Extraction code: u4uy

1.9 QT graphic programming

1.9.1 establishment of the project:

1.9.2 project realization:

QT       += core gui texttospeech

#Include < qtexttospeech > / / speaking class; You need to add a language conversion class in pro: texttospeech

QTextToSpeech *x;   		//Talking class

x = new QTextToSpeech;      //Construct a speaking class

x->say("Have you eaten");         //Say a word

x->say(ui->lineEdit->text());         //Text voice broadcast in extraction box

QT graphic programming example code link:
In the untitled4 folder: https://pan.baidu.com/s/1_sonChu0NyJhtJkmEsRSKQ
Extraction code: u4uy

1.10 signal and slot

1.10.1 signal and slot

Signal and slot mechanism is a main feature of Qt, which is the most different part of Qt from other toolkits
A callback is a function pointer that is called when an event occurs, and any function can be scheduled as a callback
Signals and slots are more dynamic
Qt uses signal and slot to realize communication between object components.

1.10.2 signal and slot:

When the signal is transmitted, the QT code will call back the slot function connected to it
Signals will be processed by meta objects, and moc will be automatically translated into C + + code
The declaration of the signal is not in the cpp file, but in the header file

1.10.3 signal and slot function

Slot function is an ordinary C + + member function, which can be called normally
The slot function can have a return value or no return value
There are three access permissions for slot functions: public slots, private slots and protected
slots. The access rights of the slot function determine who can be associated with it

1.10.4. Signal and slot: connection

1.10.5 signal and slot: send signal

Signal}- is usually sent by Qt during event processing. If the program needs to trigger the signa l itself, use emit.
The usage syntax is as follows
emit signal

1.10.6 signal and slot: cancel connection