A Practical Guide to Designing C++ Graphical Programming Interfaces

Answer: Using the Qt framework to design a GUI in C++ includes the following steps: creating a header file to declare the GUI; creating a source file to implement the GUI; creating a UI file to describe the layout; compiling and running.

C++ Graphical Programming Interface (GUI) Design Practical Guide

Introduction

GUI is crucial for creating user-friendly applications. In this article, we will learn how to design and implement a GUI in C++ using the Qt framework.

Qt Framework

Qt is a cross-platform GUI framework that supports multiple platforms (such as Windows, macOS, and Linux). It provides a collection of GUI widgets that can be used to build complex user interfaces quickly and easily.

Code structure

A simple Qt GUI program usually contains the following three files:

• Header file: Declare GUI classes and methods.
• Source file: Classes and methods that implement GUI.
• UI file: An XML file that describes the GUI layout.

Practical Case: Simple Calculator

Let’s create a simple calculator application to demonstrate the GUI design process:

Header file (calculator_widget.h)

#ifndef CALCULATOR_WIDGET_H
#define CALCULATOR_WIDGET_H

#include <QWidget>
#include <QGridLayout>
#include <QPushButton>
#include <QLineEdit>

class CalculatorWidget : public QWidget {
    Q_OBJECT

public:
    CalculatorWidget(QWidget *parent = nullptr);

private slots:
    void numberButtonClicked();
    void operatorButtonClicked();
    void equalsButtonClicked();

private:
    QGridLayout *gridLayout;
    QPushButton *numberButtons[10];
    QPushButton *operatorButtons[4];
    QPushButton *equalsButton;
    QLineEdit *display;
};

#endif // CALCULATOR_WIDGET_H

Source file (calculator_widget.cpp)

#include "calculator_widget.h"

CalculatorWidget::CalculatorWidget(QWidget *parent)
    : QWidget(parent)
{
    // 创建布局
    gridLayout = new QGridLayout;
    setLayout(gridLayout);

    // 创建数字按钮
    for (int i = 0; i < 10; i++) {
        numberButtons[i] = new QPushButton(QString::number(i));
        gridLayout->addWidget(numberButtons[i], i / 3, i % 3);
        connect(numberButtons[i], &QPushButton::clicked, this, &CalculatorWidget::numberButtonClicked);
    }

    // 创建运算符按钮
    operatorButtons[0] = new QPushButton("+");
    operatorButtons[1] = new QPushButton("-");
    operatorButtons[2] = new QPushButton("*");
    operatorButtons[3] = new QPushButton("/");
    for (int i = 0; i < 4; i++) {
        gridLayout->addWidget(operatorButtons[i], (i + 1) / 2, 3);
        connect(operatorButtons[i], &QPushButton::clicked, this, &CalculatorWidget::operatorButtonClicked);
    }

    // 创建等号按钮
    equalsButton = new QPushButton("=");
    gridLayout->addWidget(equalsButton, 4, 3);
    connect(equalsButton, &QPushButton::clicked, this, &CalculatorWidget::equalsButtonClicked);

    // 创建显示屏
    display = new QLineEdit;
    gridLayout->addWidget(display, 0, 0, 1, 3);
}

void CalculatorWidget::numberButtonClicked()
{
    QPushButton *button = qobject_cast<QPushButton*>(sender());
    display->setText(display->text() + button->text());
}

void CalculatorWidget::operatorButtonClicked()
{
    QPushButton *button = qobject_cast<QPushButton*>(sender());
    // 保存操作数和运算符
    operator = button->text();
    operand = display->text();
}

void CalculatorWidget::equalsButtonClicked()
{
    // 计算结果
    int result = 0;
    if (operator == "+") {
        result = operand.toInt() + display->text().toInt();
    } else if (operator == "-") {
        result = operand.toInt() - display->text().toInt();
    } else if (operator == "*") {
        result = operand.toInt() * display->text().toInt();
    } else if (operator == "/") {
        result = operand.toInt() / display->text().toInt();
    }
    // 显示结果
    display->setText(QString::number(result));
}

Compile and run

To compile and run the application, you need to install the Qt framework and use the following command:

g++ -std=c++11 -I/usr/include/qt5 calculator_widget.cpp -o calculator

Run the command ./calculator to start the calculator application.

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