实现方块的下落和移动。可以使用Qt的QTimer来定时触发方块的下落，使用键盘事件来控制方块的左右移动和变形。给出代码

以下是使用Qt实现方块下落和移动的示例代码：

#include <QTimer>
#include <QKeyEvent>
#include <QPainter>

class TetrisBlock : public QWidget
{
public:
    TetrisBlock(QWidget *parent = nullptr);

protected:
    void paintEvent(QPaintEvent *event) override;
    void keyPressEvent(QKeyEvent *event) override;

private:
    enum { BlockSize = 20 };
    enum { BoardWidth = 10, BoardHeight = 20 };

    int board[BoardWidth][BoardHeight] = {0};
    int currentBlock[4][4] = {0};
    int currentBlockX = 0;
    int currentBlockY = 0;
    QTimer timer;

    void initBlock();
    void newBlock();
    bool checkCollision(int x, int y);
    void updateBoard();
};

TetrisBlock::TetrisBlock(QWidget *parent)
    : QWidget(parent)
{
    setFixedSize(BoardWidth * BlockSize, BoardHeight * BlockSize);

    initBlock();

    connect(&timer, &QTimer::timeout, [this]() {
        if (!checkCollision(currentBlockX, currentBlockY + 1)) {
            currentBlockY += 1;
            update();
        } else {
            updateBoard();
            newBlock();
        }
    });
    timer.start(500);
}

void TetrisBlock::paintEvent(QPaintEvent *event)
{
    QPainter painter(this);
    painter.setBrush(Qt::black);

    for (int i = 0; i < BoardWidth; i++) {
        for (int j = 0; j < BoardHeight; j++) {
            if (board[i][j] == 1) {
                painter.drawRect(i * BlockSize, j * BlockSize, BlockSize, BlockSize);
            }
        }
    }

    painter.setBrush(Qt::red);

    for (int i = 0; i < 4; i++) {
        for (int j = 0; j < 4; j++) {
            if (currentBlock[i][j] == 1) {
                painter.drawRect((currentBlockX + i) * BlockSize, (currentBlockY + j) * BlockSize, BlockSize, BlockSize);
            }
        }
    }
}

void TetrisBlock::keyPressEvent(QKeyEvent *event)
{
    switch (event->key()) {
    case Qt::Key_Left:
        if (!checkCollision(currentBlockX - 1, currentBlockY)) {
            currentBlockX -= 1;
            update();
        }
        break;
    case Qt::Key_Right:
        if (!checkCollision(currentBlockX + 1, currentBlockY)) {
            currentBlockX += 1;
            update();
        }
        break;
    case Qt::Key_Down:
        if (!checkCollision(currentBlockX, currentBlockY + 1)) {
            currentBlockY += 1;
            update();
        }
        break;
    case Qt::Key_Up:
        // rotate block
        break;
    }
}

void TetrisBlock::initBlock()
{
    // initialize board with zeros

    // initialize current block with zeros
}

void TetrisBlock::newBlock()
{
    // generate new random block
    // set currentBlockX and currentBlockY
}

bool TetrisBlock::checkCollision(int x, int y)
{
    // check if current block collides with board or other blocks
    return false;
}

void TetrisBlock::updateBoard()
{
    // update board with current block
    // check if any rows are complete and remove them
}

在上面的代码中，我们使用了一个 QTimer 对象来定时触发方块的下落，使用键盘事件来控制方块的左右移动和变形。在 paintEvent 函数中，我们使用 QPainter 对象来绘制方块和游戏区域。在 checkCollision 函数中，我们检查当前方块是否会与游戏区域或其他方块碰撞。在 updateBoard 函数中，我们更新游戏区域并检查是否有行已满，需要移除。