QT QMediaPlayer音频视频播放器

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用QT做了一个简单的媒体播放器，UI比较粗糙但用起来还行。功能有基本的播放暂停功能，并支持拖拽。具体步骤如下。

首先建一个QT GUI程序，widget选MainWindow或者Widget都可以，我选的是MainWindow。

建好后在pro文件中添加以下语句，为了引用QT多媒体：

QT       += multimedia multimediawidgets

绘制GUI如下：

上方一个widget，由QVideoWidget的子类提升而来。下方是一个QSlider，用来显示播放进度。最下面是三个按钮，用来打开和播放。继承QVideoWidget，widget提升时候用到。videowidget.h。

#ifndef VIDEOWIDGET_H
#define VIDEOWIDGET_H
#include <QVideoWidget>class VideoWidget : public QVideoWidget
{Q_OBJECT
public:VideoWidget(QWidget *parent = nullptr);~VideoWidget();
};#endif // VIDEOWIDGET_H

videowidget.cpp

#include "videowidget.h"
#include <QDebug>VideoWidget::VideoWidget(QWidget *parent) :QVideoWidget (parent)
{
}VideoWidget::~VideoWidget()
{}

头文件mainwindow.h

#ifndef MAINWINDOW_H
#define MAINWINDOW_H#include <QMainWindow>
#include <QMediaPlayer>
#include <QMediaPlaylist>
#include "videowidget.h"
#include <QFileDialog>
#include <QLabel>namespace Ui {
class MainWindow;
}class MainWindow : public QMainWindow
{Q_OBJECTpublic:explicit MainWindow(QWidget *parent = nullptr);~MainWindow();void addToPlaylist(const QStringList &fileNames);private slots:void openFile(QString filename = "");void playFile();void stopVideo();void positionChange(qint64 position);protected:void dragEnterEvent(QDragEnterEvent *);void dropEvent(QDropEvent *);void wheelEvent(QWheelEvent *event);bool eventFilter(QObject *obj, QEvent *event);private:Ui::MainWindow *ui;QMediaPlayer *m_player;QString m_fileName;QMediaPlaylist *m_playlist;QMediaPlayer::State m_playerState;bool b_moveSlider;QLabel *timeStatus;};#endif // MAINWINDOW_H

源文件videowidget.cpp

#include "mainwindow.h"
#include "ui_mainwindow.h"
#include <QtDebug>
#include <QDragEnterEvent>
#include <QDropEvent>
#include <QList>
#include <QMimeData>
#include <QTime>
#include <QWheelEvent>MainWindow::MainWindow(QWidget *parent) :QMainWindow(parent),ui(new Ui::MainWindow)
{ui->setupUi(this);setWindowIcon(QIcon("://cd"));setAcceptDrops(true);m_player = new QMediaPlayer;m_playlist = new QMediaPlaylist;m_player->setPlaylist(m_playlist);m_player->setVideoOutput(ui->widget);b_moveSlider = false;//绑定信号槽connect(ui->bt_Open, SIGNAL(clicked()), this, SLOT(openFile()));connect(ui->bt_Play, SIGNAL(clicked()), this, SLOT(playFile()));connect(ui->bt_Stop, SIGNAL(clicked()), this, SLOT(stopVideo()));connect(m_player, SIGNAL(positionChanged(qint64)), this, SLOT(positionChange(qint64)));connect(m_player, &QMediaPlayer::mediaStatusChanged, this, [=] (QMediaPlayer::MediaStatus status) {if (status == QMediaPlayer::MediaStatus::EndOfMedia){playFile();}});timeStatus = new QLabel(this);timeStatus->setFrameStyle(QFrame::Box|QFrame::Sunken);ui->statusBar->addPermanentWidget(timeStatus);ui->progressBar->installEventFilter(this);
}MainWindow::~MainWindow()
{delete ui;
}void MainWindow::addToPlaylist(const QStringList &fileNames)
{foreach (QString const &name, fileNames){QFileInfo fileInfo(name);if (fileInfo.exists()){QUrl url = QUrl::fromLocalFile(fileInfo.absoluteFilePath());if (fileInfo.suffix().toLower() == "m3u"){m_playlist->load(url);}else{m_playlist->addMedia(url);}}}
}void MainWindow::openFile(QString filename)
{QStringList fileNames;if (filename.length() > 0){fileNames.append(filename);}else {fileNames = QFileDialog::getOpenFileNames(this, tr("Open Files"));}if (fileNames.length() <= 0){return;}int index = m_playlist->currentIndex();if (index >= 0){m_player->pause();m_playerState = QMediaPlayer::PausedState;m_playlist->removeMedia(index);}addToPlaylist(fileNames);playFile();positionChange(0);setWindowTitle(m_player->currentMedia().canonicalUrl().fileName());//在title处显示文件名
}void MainWindow::playFile()
{if (m_player->playlist()->isEmpty()){return;}if (m_playerState != QMediaPlayer::PlayingState){m_playerState = QMediaPlayer::PlayingState;m_player->play();ui->bt_Play->setText(tr("暂停"));}else{m_playerState = QMediaPlayer::PausedState;m_player->pause();ui->bt_Play->setText(tr("播放"));}}void MainWindow::stopVideo()
{m_playerState = QMediaPlayer::StoppedState;m_player->stop();ui->bt_Play->setText(tr("播放"));positionChange(0);
}
void MainWindow::positionChange(qint64 position)
{if(m_player->duration()/1000 != ui->progressBar->maximum()){ui->progressBar->setMaximum(static_cast<int>(m_player->duration()/1000));}ui->progressBar->setValue(static_cast<int>(position/1000));QTime initTime(0, 0, 0);QTime curtime = initTime.addMSecs(static_cast<int>(position));QTime totaltime = initTime.addMSecs(static_cast<int>(m_player->duration()));timeStatus->clear();timeStatus->setText(curtime.toString() + "/" +totaltime.toString());
}void MainWindow::dragEnterEvent(QDragEnterEvent *event)
{event->acceptProposedAction();QWidget::dragEnterEvent(event);
}void MainWindow::dropEvent(QDropEvent *event)
{QList<QUrl> urls = event->mimeData()->urls();if (urls.isEmpty()){return;}openFile(urls.first().toLocalFile());QWidget::dropEvent(event);
}void MainWindow::wheelEvent(QWheelEvent *event)
{QPoint numDegrees = event->angleDelta();int volume = m_player->volume();if (numDegrees.y() > 0){volume++;}else{volume--;}m_player->setVolume(volume);QMainWindow::wheelEvent(event);
}bool MainWindow::eventFilter(QObject *obj, QEvent *event)
{if (obj == ui->progressBar){if (event->type() == QEvent::MouseButtonRelease){//获取当前鼠标位置int currentX = static_cast<QMouseEvent*>(event)->x();//计算当前位置占整个slider的百分比double percentage = currentX*1.0/ui->progressBar->width();//计算具体只int value = percentage*(ui->progressBar->maximum() - ui->progressBar->minimum()) + ui->progressBar->minimum();ui->progressBar->setValue(value);qDebug()<<ui->progressBar->value();qint64 newValue = ui->progressBar->value() * 1000;if (!m_player->currentMedia().isNull()){m_player->setPosition(newValue);}}else if (event->type() == QEvent::MouseButtonPress){return true;}}return QMainWindow::eventFilter(obj, event);
}

直接获得媒体长度是0，需要用connect(m_player, SIGNAL(positionChanged(qint64)), this, SLOT(positionChange(qint64)));来获得positionChanged信号，才能得到媒体长度以及播放位置。

在用鼠标拖动slider更改播放位置时，如果移动鼠标到某个位置不放，会有播放位置来回跳动的问题。解决方法是移动鼠标时候断开positionChanged()信号，等放开鼠标后再连接。