QT note 2

Take the book back , Children's shoes that have no foundation or can't understand can be taken a quick look QT note 1_ eight two x The blog of -CSDN Blog

This time we mainly realize the switching function between the two windows

1 New window

        ① Right click on the project folder , choice “ Add new file ” or Add New...（ Different versions are displayed differently ）

         ② choice C++ -> C++ Class, And then click choose

         ③ there Name I could just write , I wrote it SubWidget, however Base class Be sure to choose QWidget

         ④ Next step , complete , There will be a new window . Engineering documents will also appear in the following documents ：

2 Switch between two windows

  After creating a new window , Our goal has become ： Click a button in the main window , Sub windows can be displayed , The main window is hidden ; Click the button of the sub window , The main window shows , The child window is hidden

2.1 main window -> child window

        ① Yes mainwidget.h operation . First , Declare a new button b3; secondly , Declare the existence of a window , Tell the main window ： You have a little brother ; Last , Add a custom slot function changeWin() Used to perform the task of switching windows .

#ifndef MAINWIDGET_H
#define MAINWIDGET_H

#include <QWidget>
#include <QPushButton>
#include "subwidget.h"  // Sub window header file 

class MainWidget : public QWidget
{
    Q_OBJECT

public:
    MainWidget(QWidget *parent = 0);
    ~MainWidget();

    void myslot();
    void changeWin();// Switch the slot function of the window 

private:
    QPushButton b1;
    QPushButton *b2;
    QPushButton b3;    // new b3 Button 

    SubWidget w1;        // Declare child windows w1
};

#endif // MAINWIDGET_H

        ② Yes mainwidget.cpp operation .

         First define changeWin function , Code + Explain the following

void MainWidget::changeWin()
{
    // The sub window shows 
    w1.show();
    // This window hides 
    this->hide();
}

        secondly , initialization b3, Then write the signal and slot function , Code + Explain the following

    b3.setParent(this);    // Set up b3 Parent class of 
    b3.setText(" Switch to sub window ");    // Set up b3 The text of 
    b3.move(50, 50);        // Set up b3 The location of 

    connect(&b3, &QPushButton::released, this, &MainWidget::changeWin);// When b3 When releasing , Switch windows 

        Only this and nothing more , We can call the sub window through the main window .

2.2 child window -> main window

        It is much more troublesome for a child window to call the main window , Like the boss can say ： petty thief , Get me an express . You can't tell the boss ： Lao Li , Buy me a pack of cigarettes . You can only say ： Boss , Do you think this plan is feasible , The boss will deal with it if he is interested , If you are not interested, just ignore it . There is a truth about the relationship between the sub window and the main window .

        The main window can call the sub window freely , But the sub window needs to call the main window and send the application signal , The main window can choose to process or not .

        ① Yes subwidget.h To operate . First, define a button b, Then define a slot function to send signals , Finally, define a signal . The code is as follows

#ifndef SUBWIDGET_H
#define SUBWIDGET_H

#include <QWidget>
#include <QPushButton>

class SubWidget : public QWidget
{
    Q_OBJECT
public:
    explicit SubWidget(QWidget *parent = nullptr);

    void sendSlot();    // Slot function for sending signal 

signals:
    /*  The signal must have signals Keyword to declare 
     *  The signal has no return value , But you can have parameters 
     *  A signal is a declaration of a function , Just declare , There is no need to define 
     *  Use ：emit mySignal();
    */

    void mySignal();    // The transmitted signal 

public slots:

private:
    QPushButton b;        // Declared button 
};

#endif // SUBWIDGET_H

        ② Yes subwidget.cpp To operate .  First initialize the button , Then define the signal and slot , Finally, the slot function sends a signal .

#include "subwidget.h"

SubWidget::SubWidget(QWidget *parent) : QWidget(parent)
{
    this->setWindowTitle("Bro");    // Set the sub window name 
    b.setParent(this);              // Set the position of the sub window 
    b.setText(" Switch to the main window ");       // Set button text 

    connect(&b, &QPushButton::clicked, this, &SubWidget::sendSlot);    // When the button is clicked , Trigger sendslot function 

    resize(400, 300);            // Control the page size to 400*300
}

void SubWidget::sendSlot()
{
    emit mySignal();        // send out mySignal The signal ; Send using emit
}

        The next step is to see how the main window handles this signal

        ③ stay mainwidget.h Add a declaration of signal processing function in .

public:
void dealSub();

        ④ stay mainwidget.cpp Signal processing in . First, in the mainwidget Add such a paragraph to the function ：

        

connect(&w1, &SubWidget::mySignal, this, &MainWidget::dealSub);
// When child window w1 Sending signal mySignal when , current window （this） perform dealSub

        ⑤ Definition dealSub

        

void MainWidget::dealSub()
{
    // The child window is hidden 
    w1.hide();
    // The main window shows 
    this->show();
}

Only this and nothing more , The function of calling each other between the main window and the sub window is realized .

Reference course ： Black horse programmer Qt（ The first part ）_ Bili, Bili _bilibili