写一个QT的音乐播放器

好的，下面是一个使用QT实现的简单的音乐播放器的代码：

#include <QApplication>
#include <QWidget>
#include <QPushButton>
#include <QVBoxLayout>
#include <QFileDialog>
#include <QMediaPlayer>
#include <QSlider>
#include <QLabel>

class MusicPlayer : public QWidget
{
public:
    MusicPlayer(QWidget *parent = 0);
    ~MusicPlayer();

private slots:
    void openFile();
    void playFile();
    void pauseFile();
    void stopFile();
    void changeVolume(int volume);

private:
    QPushButton *openButton;
    QPushButton *playButton;
    QPushButton *pauseButton;
    QPushButton *stopButton;
    QSlider *volumeSlider;
    QLabel *titleLabel;
    QMediaPlayer *player;
};

MusicPlayer::MusicPlayer(QWidget *parent)
    : QWidget(parent)
{
    openButton = new QPushButton(tr("打开"));
    playButton = new QPushButton(tr("播放"));
    pauseButton = new QPushButton(tr("暂停"));
    stopButton = new QPushButton(tr("停止"));
    volumeSlider = new QSlider(Qt::Horizontal);
    titleLabel = new QLabel(tr("请选择音乐文件"));

    player = new QMediaPlayer(this);
    connect(openButton, SIGNAL(clicked()), this, SLOT(openFile()));
    connect(playButton, SIGNAL(clicked()), this, SLOT(playFile()));
    connect(pauseButton, SIGNAL(clicked()), this, SLOT(pauseFile()));
    connect(stopButton, SIGNAL(clicked()), this, SLOT(stopFile()));
    connect(volumeSlider, SIGNAL(valueChanged(int)), this, SLOT(changeVolume(int)));
    connect(player, SIGNAL(metaDataChanged()), this, SLOT(updateTitle()));

    QVBoxLayout *layout = new QVBoxLayout;
    layout->addWidget(titleLabel);
    layout->addWidget(openButton);
    layout->addWidget(playButton);
    layout->addWidget(pauseButton);
    layout->addWidget(stopButton);
    layout->addWidget(volumeSlider);

    setLayout(layout);
}

MusicPlayer::~MusicPlayer()
{

}

void MusicPlayer::openFile()
{
    QString fileName = QFileDialog::getOpenFileName(this, tr("打开文件"), QDir::homePath(), tr("音乐文件 (*.mp3 *.wav)"));
    if (!fileName.isEmpty()) {
        player->setMedia(QUrl::fromLocalFile(fileName));
        titleLabel->setText(QFileInfo(fileName).fileName());
    }
}

void MusicPlayer::playFile()
{
    player->play();
}

void MusicPlayer::pauseFile()
{
    player->pause();
}

void MusicPlayer::stopFile()
{
    player->stop();
}

void MusicPlayer::changeVolume(int volume)
{
    player->setVolume(volume);
}

void MusicPlayer::updateTitle()
{
    titleLabel->setText(player->metaData(QMediaMetaData::Title).toString());
}

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

    MusicPlayer player;
    player.show();

    return app.exec();
}

这个播放器包括打开、播放、暂停、停止、调节音量和显示歌曲标题等功能。你可以通过 `QFileDialog` 打开音乐文件，然后使用 `QMediaPlayer` 播放音乐。同时，你还可以使用 `QSlider` 控件来调节音量大小，并且在播放时显示歌曲标题。