One 、QT File analysis

1. Project documents (.pro)

In the created Qt The project will automatically generate a  .pro Project files for , This file records some attribute information of the project . Generally used to add other modules , Or add an external library (OpenCV) File path .

2.mian.cpp file

The entry function of the program mian() The function is implemented here , It controls the operation of the program and the display of the window interface .

#include "mainwindow.h"  // Generated window class header file 

#include <QApplication>  // Header file of application class 

int main(int argc, char *argv[])
{
    // Create application objects , And there can only be one instantiated object 
    // The role of this class ： Detect trigger events , Loop events and handle 
    QApplication a(argc, argv);

    // Create a window class object 
    MainWindow w;
    // Display window 
    w.show();
    // The application object starts the event loop , Ensure that the application does not exit 
    return a.exec();
}

3.mainwindow.ui Design documents

stay Qt Each window in the corresponds to an editable visual interface , This interface corresponds to a xml File format , Generally, it is not necessary to xml Edit this file in the format , Just know about the file structure . It can be done by Qt Creator Design .

4.mainwindow.h The header file

This file is the header file corresponding to the window interface . Mainly to achieve MainWindow The definition of a class

//Qt Standard window class header file 
#include <QMainWindow>

QT_BEGIN_NAMESPACE
//mainwindow.ui There is also a class called  MainWindow,  Put this class into the namespace  Ui  in 
namespace Ui { class MainWindow; }
QT_END_NAMESPACE

class MainWindow : public QMainWindow
{
    // Macro definition ： Use Qt Signal slot mechanism 
    Q_OBJECT

public:
    MainWindow(QWidget *parent = nullptr);
    ~MainWindow();

private:
    // Define that the pointer points to the window UI object 
    Ui::MainWindow *ui;
};

5.mainwindow.cpp Source file

Implementation class MainWindow The implementation of class member functions and will Ui Interface design mainwindow And the window mainwindow Make correlation .

MainWindow::MainWindow(QWidget *parent)
    : QMainWindow(parent)
    , ui(new Ui::MainWindow) // establish ui::MainWindow An instantiated object of 
{
    // take mainwindow.ui The instantiated object of is associated with the object of the current class 
    // Make two classes with the same name one 
    ui->setupUi(this);
}

Two 、 Basic window class

Qt Common window classes are 3 individual QMainWindow,QDialog,QWidget, When creating a window class , You need to make your own window class continue one of the three window classes .

1.QWidget

① The base class of all window classes
②Qt Control in ( Button , Input box , Radio buttons …) Also belongs to window , Base classes are all QWidget
③ It can be embedded in other windows ： No borders ( When instantiating a window, you need to specify the parent window )
④ It can be displayed separately without embedding ： Independent window , There's a border ( There is no need to specify the parent window when instantiating the window )

Therefore, the display methods of corresponding embedded windows and non embedded windows are different .

Do not embed windows ： You need to call a function to display ,QWidget Is the base class for all window classes , Call this provided show() Method can display any window

    //QWidget Class instantiation ( Do not embed windows )
    //explicit testwidget(QWidget *parent = nullptr);
    // Don't specify wid The parent of the object , Do not embed windows 
    testwidget* wid = new testwidget;
    //  Display window ： A window independent of the main window 
    wid->show();

  Embedded window ： Attached to a large window , As part of the big window , The large window is the parent window of the embedded window , When the parent window is displayed , The embedded window is also displayed .

// Specify the parent object when creating the window class , Embedded window ,
// When the parent window is displayed , The sub window is also displayed , Child windows have no borders 
testwidget* wid = new testwidget(this);

2.QDialog

Dialog class , Cannot be embedded in other windows .

Non modal display ：

    // Create dialog window 
    testDialog* dig = new testDialog(this);
    // Non model display 
    dig->show();

Modal display ：

    // Create dialog window 
    testDialog* dig = new testDialog(this);
    // Model display , call exec Show 
    // Block the execution of the program 
    dig->exec();

Modal display only after closing the dialog box can the program perform the next operation .

void QWidget::show();    // Displays the current window and its child windows

QWidget Is the base class for all window classes , call show() Method can display any window （ Non modal display ）

[virtual slot] int QDialog::exec();

  Modal display of dialog window

3.QMainWindow

① There is a toolbar , status bar , menu bar , Later chapters will introduce this window in detail
② Cannot be embedded in other windows

Summary ：