Qt 6 跨平台开发完全指南

cmake_minimum_required(VERSION 3.16)
project(HelloQt VERSION 1.0 LANGUAGES CXX)
 
set(CMAKE_CXX_STANDARD 17)
set(CMAKE_CXX_STANDARD_REQUIRED ON)
set(CMAKE_AUTOMOC ON)   # 自动处理 Q_OBJECT 元对象编译
 
find_package(Qt6 REQUIRED COMPONENTS Widgets)
qt_standard_project_setup()
 
qt_add_executable(HelloQt
    main.cpp
    MainWindow.cpp
    MainWindow.h
)
 
target_link_libraries(HelloQt PRIVATE Qt6::Widgets)

#include <QApplication>
#include <QLabel>

int main(int argc, char *argv[])
{
    QApplication app(argc, argv);

    QLabel label("Hello, Qt 6!");
    label.resize(320, 120);
    label.show();

    return app.exec();
}

#include <QObject>
#include <QDebug>

class Counter : public QObject
{
    Q_OBJECT
public:
    explicit Counter(QObject *parent = nullptr) : QObject(parent), m_value(0) {}

    int value() const { return m_value; }

public slots:
    void setValue(int v)
    {
        if (v != m_value) {
            m_value = v;
            emit valueChanged(v);   // 发射信号
        }
    }

signals:
    void valueChanged(int newValue);

private:
    int m_value;
};

// 新语法（编译期检查，推荐）
connect(&counter, &Counter::valueChanged,
        &label, &QLabel::setNum);

// Lambda 写法
connect(&counter, &Counter::valueChanged, this, [](int v) {
    qDebug() << "new value:" << v;
});

// 老式字符串语法（运行时解析，不推荐，易因拼写错误静默失败）
connect(&counter, SIGNAL(valueChanged(int)),
        &label, SLOT(setNum(int)));

QString name = "Alice";
int score = 98;
QString msg = QString("%1 的成绩是 %2 分").arg(name).arg(score);
// 输出：Alice 的成绩是 98 分

#include <QMainWindow>
#include <QMenuBar>
#include <QStatusBar>
#include <QTextEdit>

class MainWindow : public QMainWindow
{
    Q_OBJECT
public:
    explicit MainWindow(QWidget *parent = nullptr)
        : QMainWindow(parent)
    {
        auto *editor = new QTextEdit(this);
        setCentralWidget(editor);                    // 中央控件

        auto *fileMenu = menuBar()->addMenu("文件"); // 菜单栏
        fileMenu->addAction("退出", this, &QWidget::close);

        statusBar()->showMessage("就绪");            // 状态栏
        setWindowTitle("文档编辑器");
        resize(800, 600);
    }
};

#include <QVBoxLayout>
#include <QHBoxLayout>
#include <QPushButton>
#include <QLineEdit>

auto *edit = new QLineEdit;
auto *btn  = new QPushButton("发送");
auto *list = new QListWidget;

auto *topLayout = new QHBoxLayout;   // 水平：输入框 + 按钮
topLayout->addWidget(edit, 1);       // stretch=1，输入框占据剩余空间
topLayout->addWidget(btn);

auto *mainLayout = new QVBoxLayout;  // 垂直：顶部一行 + 列表
mainLayout->addLayout(topLayout);
mainLayout->addWidget(list, 1);

auto *window = new QWidget;
window->setLayout(mainLayout);
window->show();

bool MainWindow::eventFilter(QObject *watched, QEvent *event) override
{
    if (watched == m_input && event->type() == QEvent::KeyPress) {
        auto *keyEvent = static_cast<QKeyEvent *>(event);
        if (keyEvent->key() == Qt::Key_Return) {
            onSendClicked();          // 拦截回车键
            return true;              // 事件被消费
        }
    }
    return QMainWindow::eventFilter(watched, event);
}

class Worker : public QThread
{
    Q_OBJECT
protected:
    void run() override
    {
        // 耗时的计算任务
        emit progress(42);
    }
signals:
    void progress(int percent);
};

auto *thread = new QThread;
auto *worker = new Worker;                 // 普通 QObject

worker->moveToThread(thread);              // 把 worker 移到子线程
connect(thread, &QThread::started, worker, &Worker::doWork);
connect(worker, &Worker::finished, thread, &QThread::quit);
thread->start();

#include <QtConcurrent>
#include <QFutureWatcher>

QFuture<int> future = QtConcurrent::run([this] {
    return heavyCompute();                 // 自动在线程池中执行
});
QFutureWatcher<int> *watcher = new QFutureWatcher<int>(this);
connect(watcher, &QFutureWatcher<int>::finished, this, [watcher] {
    qDebug() << "结果：" << watcher->result();
});
watcher->setFuture(future);

#include <QNetworkAccessManager>
#include <QNetworkReply>

QNetworkAccessManager *manager = new QNetworkAccessManager(this);

QNetworkRequest request(QUrl("https://api.example.com/data"));
request.setHeader(QNetworkRequest::ContentTypeHeader, "application/json");

QNetworkReply *reply = manager->post(request, QByteArray("{\"q\":\"qt\"}"));

connect(reply, &QNetworkReply::finished, this, [reply] {
    if (reply->error() == QNetworkReply::NoError) {
        qDebug() << reply->readAll();      // 读取响应体
    } else {
        qDebug() << "请求失败:" << reply->errorString();
    }
    reply->deleteLater();                  // 必须释放
});

class StringListModel : public QAbstractListModel
{
    Q_OBJECT
public:
    int rowCount(const QModelIndex &parent = QModelIndex()) const override
    {
        return parent.isValid() ? 0 : m_data.size();
    }

    QVariant data(const QModelIndex &index, int role) const override
    {
        if (!index.isValid() || role != Qt::DisplayRole)
            return QVariant();
        return m_data.at(index.row());
    }

private:
    QStringList m_data;
};

QListView *view = new QListView;
StringListModel *model = new StringListModel;
view->setModel(model);

// 错误：widget 是栈对象，main 返回前就被销毁
int main(int argc, char *argv[]) {
    QApplication app(argc, argv);
    QWidget w;          // 栈对象
    w.show();
    return app.exec();  // 如果 show 后立刻被销毁就会闪退
}

QPointer<QLabel> label = new QLabel;
delete label;          // 别处删除了 label
if (label) {           // QPointer 已自动置空，安全
    label->setText("...");
}

// 启用高 DPI 支持（Qt 6 默认开启，无需手动设置）
QGuiApplication::setHighDpiScaleFactorRoundingPolicy(
    Qt::HighDpiScaleFactorRoundingPolicy::PassThrough);

# Windows 下指定 Qt 安装路径
cmake -DCMAKE_PREFIX_PATH=C:/Qt/6.8.0/msvc2022_64 ..