主窗口

QMainWindow 是 Qt 中用于创建主应用程序窗口的类，提供了完整的应用程序框架。

QMainWindow 结构

┌─────────────────────────────────────┐
│  菜单栏 (Menu Bar)                   │
├─────────────────────────────────────┤
│  工具栏 (Tool Bar)                   │
├─────────────────────────────────────┤
│                                     │
│      中央部件 (Central Widget)       │
│                                     │
├─────────────────────────────────────┤
│  停靠窗口 (Dock Widgets)             │
├─────────────────────────────────────┤
│  状态栏 (Status Bar)                 │
└─────────────────────────────────────┘

基本结构

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

class MainWindow : public QMainWindow
{
    Q_OBJECT
    
public:
    MainWindow(QWidget *parent = nullptr);
    
private:
    void createMenus();
    void createToolBars();
    void createStatusBar();
    
    QTextEdit *textEdit;
};

MainWindow::MainWindow(QWidget *parent) : QMainWindow(parent)
{
    setWindowTitle("主窗口示例");
    resize(800, 600);
    
    // 设置中央部件
    textEdit = new QTextEdit(this);
    setCentralWidget(textEdit);
    
    createMenus();
    createToolBars();
    createStatusBar();
}

菜单栏

void MainWindow::createMenus()
{
    // 文件菜单
    QMenu *fileMenu = menuBar()->addMenu("文件(&F)");
    
    QAction *newAction = fileMenu->addAction("新建", this, &MainWindow::newFile);
    newAction->setShortcut(QKeySequence::New);
    newAction->setIcon(QIcon(":/icons/new.png"));
    newAction->setStatusTip("创建新文件");
    
    QAction *openAction = fileMenu->addAction("打开...", this, &MainWindow::openFile);
    openAction->setShortcut(QKeySequence::Open);
    
    fileMenu->addSeparator();
    
    QAction *saveAction = fileMenu->addAction("保存", this, &MainWindow::saveFile);
    saveAction->setShortcut(QKeySequence::Save);
    
    QAction *saveAsAction = fileMenu->addAction("另存为...", this, &MainWindow::saveAs);
    
    fileMenu->addSeparator();
    
    QAction *exitAction = fileMenu->addAction("退出", this, &QWidget::close);
    exitAction->setShortcut(QKeySequence::Quit);
    
    // 编辑菜单
    QMenu *editMenu = menuBar()->addMenu("编辑(&E)");
    
    QAction *cutAction = editMenu->addAction("剪切", textEdit, &QTextEdit::cut);
    cutAction->setShortcut(QKeySequence::Cut);
    
    QAction *copyAction = editMenu->addAction("复制", textEdit, &QTextEdit::copy);
    copyAction->setShortcut(QKeySequence::Copy);
    
    QAction *pasteAction = editMenu->addAction("粘贴", textEdit, &QTextEdit::paste);
    pasteAction->setShortcut(QKeySequence::Paste);
    
    // 帮助菜单
    QMenu *helpMenu = menuBar()->addMenu("帮助(&H)");
    helpMenu->addAction("关于", this, &MainWindow::about);
}

工具栏

void MainWindow::createToolBars()
{
    QToolBar *fileToolBar = addToolBar("文件");
    
    QAction *newAction = fileToolBar->addAction(
        QIcon(":/icons/new.png"), 
        "新建",
        this, 
        &MainWindow::newFile
    );
    
    QAction *openAction = fileToolBar->addAction(
        QIcon(":/icons/open.png"),
        "打开",
        this,
        &MainWindow::openFile
    );
    
    QAction *saveAction = fileToolBar->addAction(
        QIcon(":/icons/save.png"),
        "保存",
        this,
        &MainWindow::saveFile
    );
    
    fileToolBar->addSeparator();
    
    // 添加其他控件到工具栏
    QComboBox *zoomCombo = new QComboBox();
    zoomCombo->addItems({"50%", "75%", "100%", "125%", "150%", "200%"});
    zoomCombo->setCurrentText("100%");
    fileToolBar->addWidget(zoomCombo);
    
    // 设置工具栏属性
    fileToolBar->setMovable(true);
    fileToolBar->setFloatable(true);
    fileToolBar->setAllowedAreas(Qt::TopToolBarArea | Qt::LeftToolBarArea);
}

状态栏

void MainWindow::createStatusBar()
{
    // 显示临时消息
    statusBar()->showMessage("就绪", 3000);  // 显示3秒
    
    // 添加永久部件
    QLabel *rowLabel = new QLabel("行: 1");
    QLabel *colLabel = new QLabel("列: 1");
    QLabel *encodingLabel = new QLabel("UTF-8");
    
    statusBar()->addPermanentWidget(rowLabel);
    statusBar()->addPermanentWidget(colLabel);
    statusBar()->addPermanentWidget(encodingLabel);
    
    // 进度条
    QProgressBar *progressBar = new QProgressBar();
    progressBar->setMaximumWidth(150);
    progressBar->setMaximumHeight(16);
    statusBar()->addPermanentWidget(progressBar);
}

停靠窗口

void MainWindow::createDockWindows()
{
    // 文件浏览器停靠窗口
    QDockWidget *dock1 = new QDockWidget("文件浏览器", this);
    QTreeWidget *fileTree = new QTreeWidget();
    fileTree->setHeaderLabel("文件");
    dock1->setWidget(fileTree);
    addDockWidget(Qt::LeftDockWidgetArea, dock1);
    
    // 属性面板停靠窗口
    QDockWidget *dock2 = new QDockWidget("属性", this);
    QTableWidget *propTable = new QTableWidget(5, 2);
    propTable->setHorizontalHeaderLabels({"属性", "值"});
    dock2->setWidget(propTable);
    addDockWidget(Qt::RightDockWidgetArea, dock2);
    
    // 输出面板停靠窗口
    QDockWidget *dock3 = new QDockWidget("输出", this);
    QTextEdit *outputEdit = new QTextEdit();
    outputEdit->setReadOnly(true);
    dock3->setWidget(outputEdit);
    addDockWidget(Qt::BottomDockWidgetArea, dock3);
    
    // 视图菜单控制停靠窗口显示
    viewMenu->addAction(dock1->toggleViewAction());
    viewMenu->addAction(dock2->toggleViewAction());
    viewMenu->addAction(dock3->toggleViewAction());
}

完整示例

#include <QMainWindow>
#include <QTextEdit>
#include <QMenuBar>
#include <QToolBar>
#include <QStatusBar>
#include <QDockWidget>
#include <QTreeWidget>
#include <QFileDialog>
#include <QMessageBox>
#include <QCloseEvent>

class TextEditor : public QMainWindow
{
    Q_OBJECT
    
public:
    TextEditor(QWidget *parent = nullptr);
    
protected:
    void closeEvent(QCloseEvent *event) override;
    
private slots:
    void newFile();
    void open();
    bool save();
    bool saveAs();
    void about();
    void documentWasModified();
    
private:
    void createActions();
    void createMenus();
    void createToolBars();
    void createStatusBar();
    void readSettings();
    void writeSettings();
    bool maybeSave();
    void loadFile(const QString &fileName);
    bool saveFile(const QString &fileName);
    void setCurrentFile(const QString &fileName);
    
    QTextEdit *textEdit;
    QString curFile;
    
    QMenu *fileMenu;
    QMenu *editMenu;
    QMenu *helpMenu;
    
    QToolBar *fileToolBar;
    QToolBar *editToolBar;
    
    QAction *newAct;
    QAction *openAct;
    QAction *saveAct;
    QAction *saveAsAct;
    QAction *exitAct;
    QAction *cutAct;
    QAction *copyAct;
    QAction *pasteAct;
    QAction *aboutAct;
    QAction *aboutQtAct;
};

TextEditor::TextEditor(QWidget *parent)
    : QMainWindow(parent)
{
    textEdit = new QTextEdit(this);
    setCentralWidget(textEdit);
    
    createActions();
    createMenus();
    createToolBars();
    createStatusBar();
    
    readSettings();
    
    setWindowTitle("文本编辑器");
    setUnifiedTitleAndToolBarOnMac(true);
}

void TextEditor::createActions()
{
    newAct = new QAction(QIcon(":/images/new.png"), tr("新建"), this);
    newAct->setShortcuts(QKeySequence::New);
    newAct->setStatusTip(tr("创建新文件"));
    connect(newAct, &QAction::triggered, this, &TextEditor::newFile);
    
    openAct = new QAction(QIcon(":/images/open.png"), tr("打开..."), this);
    openAct->setShortcuts(QKeySequence::Open);
    openAct->setStatusTip(tr("打开文件"));
    connect(openAct, &QAction::triggered, this, &TextEditor::open);
    
    saveAct = new QAction(QIcon(":/images/save.png"), tr("保存"), this);
    saveAct->setShortcuts(QKeySequence::Save);
    saveAct->setStatusTip(tr("保存文件"));
    connect(saveAct, &QAction::triggered, this, &TextEditor::save);
    
    saveAsAct = new QAction(tr("另存为..."), this);
    saveAsAct->setShortcuts(QKeySequence::SaveAs);
    saveAsAct->setStatusTip(tr("以新名称保存文件"));
    connect(saveAsAct, &QAction::triggered, this, &TextEditor::saveAs);
    
    exitAct = new QAction(tr("退出"), this);
    exitAct->setShortcuts(QKeySequence::Quit);
    exitAct->setStatusTip(tr("退出应用程序"));
    connect(exitAct, &QAction::triggered, this, &QWidget::close);
    
    cutAct = new QAction(QIcon(":/images/cut.png"), tr("剪切"), this);
    cutAct->setShortcuts(QKeySequence::Cut);
    cutAct->setStatusTip(tr("剪切选中内容"));
    connect(cutAct, &QAction::triggered, textEdit, &QTextEdit::cut);
    
    copyAct = new QAction(QIcon(":/images/copy.png"), tr("复制"), this);
    copyAct->setShortcuts(QKeySequence::Copy);
    copyAct->setStatusTip(tr("复制选中内容"));
    connect(copyAct, &QAction::triggered, textEdit, &QTextEdit::copy);
    
    pasteAct = new QAction(QIcon(":/images/paste.png"), tr("粘贴"), this);
    pasteAct->setShortcuts(QKeySequence::Paste);
    pasteAct->setStatusTip(tr("粘贴剪贴板内容"));
    connect(pasteAct, &QAction::triggered, textEdit, &QTextEdit::paste);
    
    aboutAct = new QAction(tr("关于"), this);
    aboutAct->setStatusTip(tr("显示应用程序信息"));
    connect(aboutAct, &QAction::triggered, this, &TextEditor::about);
    
    aboutQtAct = new QAction(tr("关于 Qt"), this);
    aboutQtAct->setStatusTip(tr("显示 Qt 信息"));
    connect(aboutQtAct, &QAction::triggered, qApp, &QApplication::aboutQt);
}

void TextEditor::createMenus()
{
    fileMenu = menuBar()->addMenu(tr("文件(&F)"));
    fileMenu->addAction(newAct);
    fileMenu->addAction(openAct);
    fileMenu->addAction(saveAct);
    fileMenu->addAction(saveAsAct);
    fileMenu->addSeparator();
    fileMenu->addAction(exitAct);
    
    editMenu = menuBar()->addMenu(tr("编辑(&E)"));
    editMenu->addAction(cutAct);
    editMenu->addAction(copyAct);
    editMenu->addAction(pasteAct);
    
    menuBar()->addSeparator();
    
    helpMenu = menuBar()->addMenu(tr("帮助(&H)"));
    helpMenu->addAction(aboutAct);
    helpMenu->addAction(aboutQtAct);
}

void TextEditor::createToolBars()
{
    fileToolBar = addToolBar(tr("文件"));
    fileToolBar->addAction(newAct);
    fileToolBar->addAction(openAct);
    fileToolBar->addAction(saveAct);
    
    editToolBar = addToolBar(tr("编辑"));
    editToolBar->addAction(cutAct);
    editToolBar->addAction(copyAct);
    editToolBar->addAction(pasteAct);
}

void TextEditor::createStatusBar()
{
    statusBar()->showMessage(tr("就绪"));
}

下一步

继续学习绘图与图形，掌握 Qt 的 2D 绘图系统。