Creation and simple application of QPushButton button button

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Preface

stay QT In the program , Every time you add a control , You must declare the header file of the corresponding control at the beginning . If the button is QT One of the most commonly used controls in , Button controls are in English PushButton Definition , but QT There is a feature in the header file declaration of , Is to add a capital letter in front of the header file Q, The first letter of each word is capitalized .

One 、 Button creation steps

1. Define header file

#include<QPushButton>

2. First you need to create a button

QPushButton * btn1 = new QPushButton;

3. Let the buttons you set depend on the window , Here, the window parameter represents the dependent window , That is, the parent class , from c++ You can learn , You can use it here this Pointer instead of .

btn1->setParent(this);   

4. Name the button

`btn1->setText(" The first button ");  // Show text `

5. Move button , At first, the default is （0,0） Point position , Upper left corner , You can move it by setting , Move to the position you want .

btn1->move(200,200);   // Move btn1 Button 

6. Set the size of the button

btn2->resize(100,50);    // To redraw btn2 size 

7. Display button

btn1->show();

Two 、 Simple application of buttons

The functions realized here are ： Click the set button , Close the window

So you need to connect the window and the button , The English word connected is called connect
The specific use is connect（ Parameters 1, Parameters 2, Parameters 3, Parameters 4）;

Parameter one ： Signal sender
Parameter two ： Transmitted signal （ Address of function ）
Parameter 3 ： The receiver of the signal
Parameter 4 ： Processing slot function

You can know ad locum ：
Parameter 1 is button , namely btn1;
Parameter 2 is the function of clicking the button , use &QPushButton::clicked Express ;
Parameter 3 is window , Receiving a signal , by this The pointer ;
Parameter 4 is the function of closing the window , Commonly known as slot function , The closed function is &Widget::close.

therefore

// function ：  Click on “ The first button ”  Close the window 
    
    connect(btn1,&QPushButton::clicked,this,&Widget::close);

3、 ... and 、 Complete code

widget.h

#ifndef WIDGET_H
#define WIDGET_H

#include <QWidget>

class Widget : public QWidget
{
    
    Q_OBJECT    // Signal slot 
public:
    Widget(QWidget *parent = 0);
    ~Widget();
};

#endif // WIDGET_H

widget.cpp

#include "widget.h"
#include<QPushButton>

Widget::Widget(QWidget *parent) :
    QWidget(parent)
{
    
    // Create a button 
    QPushButton *btn1=new QPushButton;
    btn1->show();
    btn1->setParent(this);  // Give Way btn1 Objects depend on Widget Window 
    btn1->setText(" The first button ");  // Show text 
    btn1->move(200,200);   // Move btn1 Button 
    // function ：  Click on “ The first button ”  Close the window 
    // Parameter one ： Signal sender   Parameter two ： Transmitted signal （ Address of function ）  Parameter 3 ： The receiver of the signal   Parameter 4 ： Processing slot function 
    connect(btn1,&QPushButton::clicked,this,&Widget::close);
}

Widget::~Widget()
{
    
}

main.cpp

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

int main(int argc, char *argv[])
{
    
    QApplication a(argc, argv);    //a Application object , stay QT in , The application object has and only has one 
    Widget w;  // Window object ,Widget Parent class  ->QWidget
    w.show();   // Window object   Default will not show   Must call show Method display window 

    return a.exec();  // Let the application object enter the message loop 
}