Qt利用QDrag实现拖拽拼图功能详解

    QApplication a(argc, argv);
    MainWindow w;
    w.loadImage(QStringLiteral(":/example.jpg"));
    w.show();
    return a.exec();

public:
    MainWindow(QWidget *parent = nullptr);
    ~MainWindow();
    void loadImage(const QString &path);

public slots:
    void openImage();
    void setupPuzzle();

private slots:
    void setCompleted();

private:
    void setupMenus();
    void setupWidgets();

    QPixmap puzzleImage;
    PiecesList *piecesList;
    PuzzleWidget *puzzleWidget;

    setupMenus();
    setupWidgets();

    setSizePolicy(QSizePolicy(QSizePolicy::Fixed, QSizePolicy::Fixed));//设置大小策略
    setWindowTitle(tr("拖拽拼图"));

//打开图像(重新选择图像分割)
void MainWindow::openImage()
{
    const QString directory =
        QStandardPaths::standardLocations(QStandardPaths::PicturesLocation).value(0, QDir::homePath());
    QFileDialog dialog(this, tr("Open Image"), directory);//创建打开文件对话框
    dialog.setFileMode(QFileDialog::ExistingFile);//设置返回存在的文件名
    QStringList mimeTypeFilters;
    for (const QByteArray &mimeTypeName : QImageReader::supportedMimeTypes())
        mimeTypeFilters.append(mimeTypeName);
    mimeTypeFilters.sort(); //排序
    dialog.setMimeTypeFilters(mimeTypeFilters);
    dialog.selectMimeTypeFilter("image/jpeg");
    if (dialog.exec() == QDialog::Accepted)
        loadImage(dialog.selectedFiles().constFirst());
}

// 加载图片
void MainWindow::loadImage(const QString &fileName)
{
    QPixmap newImage;
    if (!newImage.load(fileName)) {
        QMessageBox::warning(this, tr("Open Image"),
                             tr("The image file could not be loaded."),
                             QMessageBox::Close);
        return;
    }
    puzzleImage = newImage;
    setupPuzzle();
}

//拼图完成后弹出对话框
void MainWindow::setCompleted()
{
    QMessageBox::information(this, tr("拼图完成"),
                             tr("恭喜!您已经成功拼图 \n"
                                "点击OK重新开始"),
                             QMessageBox::Ok);

    setupPuzzle();
}

void MainWindow::setupPuzzle()
{
    int size = qMin(puzzleImage.width(), puzzleImage.height());//获取图像宽度和高度的最小值
    puzzleImage = puzzleImage.copy((puzzleImage.width() - size) / 2,
        (puzzleImage.height() - size) / 2, size, size).scaled(puzzleWidget->width(),
            puzzleWidget->height(), Qt::IgnoreAspectRatio, Qt::SmoothTransformation);//缩放

    piecesList->clear();//清空List
    //切分成5*5=25张拼图
    for (int y = 0; y < 5; ++y) {
        for (int x = 0; x < 5; ++x) {
            int pieceSize = puzzleWidget->pieceSize();
            QPixmap pieceImage = puzzleImage.copy(x * pieceSize, y * pieceSize, pieceSize, pieceSize);
            piecesList->addPiece(pieceImage, QPoint(x, y));
        }
    }

    for (int i = 0; i < piecesList->count(); ++i) {
        if (QRandomGenerator::global()->bounded(2) == 1) {
            QListWidgetItem *item = piecesList->takeItem(i);
            piecesList->insertItem(0, item);
        }
    }

    puzzleWidget->clear();
}

//设置菜单栏
void MainWindow::setupMenus()
{
    QMenu *fileMenu = menuBar()->addMenu(tr("&文件"));

    QAction *openAction = fileMenu->addAction(tr("&打开..."), this, &MainWindow::openImage);
    openAction->setShortcuts(QKeySequence::Open);   //快捷键
    QAction *exitAction = fileMenu->addAction(tr("&退出"), qApp, &QCoreApplication::quit);
    exitAction->setShortcuts(QKeySequence::Quit);   //快捷键

    QMenu *gameMenu = menuBar()->addMenu(tr("&游戏"));
    gameMenu->addAction(tr("&重启"), this, &MainWindow::setupPuzzle);
}

//设置界面布局
void MainWindow::setupWidgets()
{
    QFrame *frame = new QFrame;
    QHBoxLayout *frameLayout = new QHBoxLayout(frame);//水平布局
    puzzleWidget = new PuzzleWidget(400);//新建PuzzleWidget对象,设置图像尺寸为400

    piecesList = new PiecesList(puzzleWidget->pieceSize(), this);


    connect(puzzleWidget, &PuzzleWidget::puzzleCompleted,
            this, &MainWindow::setCompleted, Qt::QueuedConnection);

    frameLayout->addWidget(piecesList);
    frameLayout->addWidget(puzzleWidget);
    setCentralWidget(frame);//中心部件
}

    void dragEnterEvent(QDragEnterEvent *event) override;
    void dragLeaveEvent(QDragLeaveEvent *event) override;
    void dragMoveEvent(QDragMoveEvent *event) override;
    void dropEvent(QDropEvent *event) override;
    void mousePressEvent(QMouseEvent *event) override;
    void paintEvent(QPaintEvent *event) override;