开始使用 Qt 编程Qt Widgets

#include "notepad.h"

#include <QApplication>

int main(int argc, char *argv[])
{
    QApplication a(argc, argv);
    Notepad w;
    w.show();
    return a.exec();
}

#include "notepad.h"

#include <QApplication>

int main(int argc, char *argv[])

    QApplication a(argc, argv);

    Notepad w;

    w.show();

    return a.exec();

<?xml version="1.0" encoding="UTF-8"?>
<ui version="4.0">
 <class>Notepad</class>
 <widget class="QMainWindow" name="Notepad">
  <property name="geometry">
   <rect>
    <x>0</x>
    <y>0</y>
    <width>800</width>
    <height>400</height>
   </rect>
  </property>
  <property name="windowTitle">
   <string>Notepad</string>
  </property>
  <widget class="QWidget" name="centralWidget">
   <layout class="QVBoxLayout" name="verticalLayout">
    <item>
     <widget class="QTextEdit" name="textEdit"/>
    </item>
   </layout>
  </widget>
  <widget class="QMenuBar" name="menuBar">
    ...

<?xml version="1.0" encoding="UTF-8"?>

<ui version="4.0">

#include <QMainWindow>

QT_BEGIN_NAMESPACE
namespace Ui {
class Notepad;
}
QT_END_NAMESPACE

class Notepad : public QMainWindow
{
    Q_OBJECT

public:
    explicit Notepad(QWidget *parent = nullptr);
    ~Notepad();

private:
    Ui::Notepad *ui;
    QString currentFile;
};

#include <QMainWindow>

namespace Ui {
class Notepad;
}

class Notepad : public QMainWindow
{
    Q_OBJECT

public:
    explicit Notepad(QWidget *parent = nullptr);

    ~Notepad();

private:
    Ui::Notepad *ui;
    QString currentFile;
};

#include "notepad.h"
#include "ui_notepad.h"

Notepad::Notepad(QWidget *parent) :
    QMainWindow(parent),
    ui(new Ui::Notepad)
{
    ui->setupUi(this);

}

#include "notepad.h"
#include "ui_notepad.h"

Notepad::Notepad(QWidget *parent) :

    QMainWindow(parent),

    ui(new Ui::Notepad)

{
    ui->setupUi(this);

Notepad::~Notepad()
{
    delete ui;
}

# Copyright (C) 2022 The Qt Company Ltd.
# SPDX-License-Identifier: LicenseRef-Qt-Commercial OR BSD-3-Clause

cmake_minimum_required(VERSION 3.16)
project(notepad LANGUAGES CXX)

find_package(Qt6
    REQUIRED COMPONENTS Core Gui Widgets
    OPTIONAL_COMPONENTS PrintSupport
)

qt_standard_project_setup()

qt_add_executable(notepad
    main.cpp
    notepad.cpp notepad.h notepad.ui
)

set_target_properties(notepad PROPERTIES
    WIN32_EXECUTABLE TRUE
    MACOSX_BUNDLE TRUE
)

target_link_libraries(notepad PRIVATE
    Qt6::Core
    Qt6::Gui
    Qt6::Widgets
)

if(TARGET Qt6::PrintSupport)
    target_link_libraries(notepad PRIVATE Qt6::PrintSupport)
endif()

# Resources:
set(notepad_resource_files
    "images/bold.png"
    "images/copy.png"
    "images/create.png"
    "images/cut.png"
    "images/edit_redo.png"
    "images/edit_undo.png"
    "images/exit.png"
    "images/font.png"
    "images/info.png"
    "images/italic.png"
    "images/new.png"
    "images/open.png"
    "images/paste.png"
    "images/pencil.png"
    "images/print.png"
    "images/save.png"
    "images/save_as.png"
    "images/underline.png"
)

qt_add_resources(notepad "notepad"
    PREFIX
        "/"
    FILES
        ${notepad_resource_files}
)

install(TARGETS notepad
    BUNDLE  DESTINATION .
    RUNTIME DESTINATION ${CMAKE_INSTALL_BINDIR}
    LIBRARY DESTINATION ${CMAKE_INSTALL_LIBDIR}
)

qt_generate_deploy_app_script(
    TARGET notepad
    OUTPUT_SCRIPT deploy_script
    NO_UNSUPPORTED_PLATFORM_ERROR
)
install(SCRIPT ${deploy_script})

void Notepad::newDocument()
{
    currentFile.clear();
    ui->textEdit->setText(QString());
}

private:
    Ui::Notepad *ui;
    QString currentFile;

void Notepad::open()
{
    QString fileName = QFileDialog::getOpenFileName(this, "Open the file");
    if (fileName.isEmpty())
        return;
    QFile file(fileName);
    currentFile = fileName;
    if (!file.open(QIODevice::ReadOnly | QFile::Text)) {
        QMessageBox::warning(this, "Warning", "Cannot open file: " + file.errorString());
        return;
    }
    setWindowTitle(fileName);
    QTextStream in(&file);
    QString text = in.readAll();
    ui->textEdit->setText(text);
    file.close();
}

void Notepad::save()
{
    QString fileName;
    // If we don't have a filename from before, get one.
    if (currentFile.isEmpty()) {
        fileName = QFileDialog::getSaveFileName(this, "Save");
        if (fileName.isEmpty())
            return;
        currentFile = fileName;
    } else {
        fileName = currentFile;
    }
    QFile file(fileName);
    if (!file.open(QIODevice::WriteOnly | QFile::Text)) {
        QMessageBox::warning(this, "Warning", "Cannot save file: " + file.errorString());
        return;
    }
    setWindowTitle(fileName);
    QTextStream out(&file);
    QString text = ui->textEdit->toPlainText();
    out << text;
    file.close();
}

void Notepad::saveAs()
{
    QString fileName = QFileDialog::getSaveFileName(this, "Save as");
    if (fileName.isEmpty())
        return;
    QFile file(fileName);

    if (!file.open(QFile::WriteOnly | QFile::Text)) {
        QMessageBox::warning(this, "Warning", "Cannot save file: " + file.errorString());
        return;
    }
    currentFile = fileName;
    setWindowTitle(fileName);
    QTextStream out(&file);
    QString text = ui->textEdit->toPlainText();
    out << text;
    file.close();
}

find_package(Qt6
    REQUIRED COMPONENTS Core Gui Widgets
    OPTIONAL_COMPONENTS PrintSupport
)

void Notepad::print()
{
#if defined(QT_PRINTSUPPORT_LIB) && QT_CONFIG(printer)
    QPrinter printDev;
#if QT_CONFIG(printdialog)
    QPrintDialog dialog(&printDev, this);
    if (dialog.exec() == QDialog::Rejected)
        return;
#endif // QT_CONFIG(printdialog)
    ui->textEdit->print(&printDev);
#endif // QT_CONFIG(printer)
}

void Notepad::selectFont()
{
    bool fontSelected;
    QFont font = QFontDialog::getFont(&fontSelected, this);
    if (fontSelected)
        ui->textEdit->setFont(font);
}

md <build_directory>
cd <build_directory>
<qt_installation_directory>\bin\qt-cmake -GNinja <source_directory>
<generator>

md notepad-build
cd notepad-build
C:\Qt\6.9.0\msvc2019_64\bin\qt-cmake -GNinja C:\Examples\notepad
ninja

cmake --build