qt实现视频播放器

大家好，又见面了，我是你们的朋友全栈君。

本篇博客介绍如何利用qMediaPlayer和qvideowidget实现视频文件(avi,mp4….)的播放，并且提供进度显示，还可以通过拖动进度条来变换播放位置。相关代码可以在我的资源里下载”基于qt的视频播放器”

pro文件：

#-------------------------------------------------
#
# Project created by QtCreator 2018-11-02T20:03:58
#
#-------------------------------------------------

QT       += core gui multimedia multimediawidgets

greaterThan(QT_MAJOR_VERSION, 4): QT += widgets

TARGET = VideoPlayer
TEMPLATE = app


SOURCES += main.cpp \
    videoplayer.cpp \
    playerslider.cpp

HEADERS  += \
    videoplayer.h \
    playerslider.h

FORMS    += \
    videoplayer.ui

main.cpp

#include "videoplayer.h"
#include <QApplication>

int main(int argc, char *argv[])
{
    QApplication a(argc, argv);
    VideoPlayer w;
    w.show();

    return a.exec();
}

VideoPlayer是我定义的播放器窗体类。它包括一个QMediaplayer,一个QVideoWidget，一个播放按钮，一个停止按钮，一个载入按钮，和进度条PlayerSlider。VideoPlayer的ui文件外观如图：

这里面的PlayerSlider继承自QSlider，行为定义如下：

#ifndef PLAYERSLIDER_H
#define PLAYERSLIDER_H

#include <QSlider>
#include <QMouseEvent>

class PlayerSlider : public QSlider
{
    Q_OBJECT
public:
    PlayerSlider(QWidget * parent = 0);
    void        setProgress(qint64);
signals:
    void        sigProgress(qint64);
private:
    bool        m_bPressed;
protected:
    void        mousePressEvent(QMouseEvent *);
    void        mouseMoveEvent(QMouseEvent *);
    void        mouseReleaseEvent(QMouseEvent *);
};

#endif // PLAYERSLIDER_H

#include "playerslider.h"

PlayerSlider::PlayerSlider(QWidget * parent) : QSlider(parent)
{
    m_bPressed = false;
}

void PlayerSlider::mousePressEvent(QMouseEvent *e)
{
    m_bPressed = true;
    QSlider::mousePressEvent(e);//必须有这句，否则手动不能移动滑块
}

void PlayerSlider::mouseMoveEvent(QMouseEvent *e)
{
    QSlider::mouseMoveEvent(e);//必须有这句，否则手动不能移动滑块
}

void PlayerSlider::mouseReleaseEvent(QMouseEvent *e)
{
    m_bPressed = false;
    qint64 i64Pos = value();
    emit sigProgress(i64Pos);

    QSlider::mouseReleaseEvent(e);//必须有这句，否则手动不能移动滑块
}

void PlayerSlider::setProgress(qint64 i64Progress)
{
    if(!m_bPressed)
        setValue(i64Progress);
}

这个类的作用有3个：1）接收QMediaPlaer发来的进度信息，更新进度条；2）当用户操作进度条时，不再让进度条响应QMediaPlaer发来的进度信息；3）当用户完成对进度条的拖动后，向QMediaPlaer发送播放位置更新信息。

另一个类是VideoPlayer，行为定义如下：

#ifndef VIDEOPLAYER_H
#define VIDEOPLAYER_H

#include <QWidget>
#include <QtMultimedia>
#include <QVideoWidget>

namespace Ui {
class VideoPlayer;
}

class VideoPlayer : public QWidget
{
    Q_OBJECT

public:
    explicit VideoPlayer(QWidget *parent = 0);
    ~VideoPlayer();

    bool            m_bReLoad;
public slots:
    void            OnSetMediaFile(void);
    void            OnSlider(qint64);
    void            OnDurationChanged(qint64);
    void            OnStateChanged(QMediaPlayer::State);
private:
    QVideoWidget    *       m_pPlayerWidget;
    QMediaPlayer    *       m_pPlayer;
    Ui::VideoPlayer *ui;
};

#endif // VIDEOPLAYER_H

#include "videoplayer.h"
#include "ui_videoplayer.h"
#include <QFileDialog>

VideoPlayer::VideoPlayer(QWidget *parent) :
    QWidget(parent),
    ui(new Ui::VideoPlayer)
{
    ui->setupUi(this);

    m_pPlayer = new QMediaPlayer;
    m_pPlayerWidget = new QVideoWidget;
    m_pPlayer->setVideoOutput(m_pPlayerWidget);
    ui->verticalLayout->addWidget(m_pPlayerWidget);

    m_pPlayerWidget->setAutoFillBackground(true);
    QPalette qplte;
    qplte.setColor(QPalette::Window, QColor(0,0,0));
    m_pPlayerWidget->setPalette(qplte);
    //载入
    connect(ui->BtnLoad, SIGNAL(clicked()), this, SLOT(OnSetMediaFile()));
    //播放
    connect(ui->BtnPlay, SIGNAL(clicked()), m_pPlayer, SLOT(play()));
    //停止
    connect(ui->BtnStop, SIGNAL(clicked()), m_pPlayer, SLOT(stop()));

    connect(m_pPlayer, SIGNAL(stateChanged(QMediaPlayer::State)), this, SLOT(OnStateChanged(QMediaPlayer::State)));

    ui->BtnStop->setEnabled(false);
    //设置滑块行为
    m_bReLoad = true;
    ui->slider->setEnabled(false);
    connect(m_pPlayer, SIGNAL(positionChanged(qint64)), this, SLOT(OnSlider(qint64)));
    connect(m_pPlayer, SIGNAL(durationChanged(qint64)), this, SLOT(OnDurationChanged(qint64)));
    connect(ui->slider, SIGNAL(sigProgress(qint64)), m_pPlayer, SLOT(setPosition(qint64)));
}

VideoPlayer::~VideoPlayer()
{
    delete m_pPlayer;
    delete m_pPlayerWidget;
    delete ui;
}

void VideoPlayer::OnSetMediaFile(void)
{
    QFileDialog dialog(this);
    dialog.setFileMode(QFileDialog::AnyFile);
    QStringList fileNames;
    if (dialog.exec())
        fileNames = dialog.selectedFiles();

    if(!fileNames.empty())
    {
        m_pPlayer->setMedia(QUrl::fromLocalFile(fileNames[0]));
        m_bReLoad = true;
        ui->slider->setValue(0);
    }
}

void VideoPlayer::OnSlider(qint64 i64Pos)
{
    ui->slider->setProgress(i64Pos);
}

void VideoPlayer::OnDurationChanged(qint64 i64Duration)
{
    if(i64Duration > 0 && m_bReLoad)
    {
        ui->slider->setRange(0, i64Duration);
        m_bReLoad = false;
    }
}


void VideoPlayer::OnStateChanged(QMediaPlayer::State enumState)
{
    if(QMediaPlayer::StoppedState == enumState)
    {
        ui->BtnPlay->setEnabled(true);
        ui->BtnStop->setEnabled(false);
        ui->slider->setEnabled(false);
    }
    else if(QMediaPlayer::PlayingState == enumState)
    {
        ui->BtnPlay->setEnabled(false);
        ui->BtnStop->setEnabled(true);
        ui->slider->setEnabled(true);
    }
}

之所以在他的构造函数里设置QPalette，是因为假如不这样，在程序启动时，m_pPlayer不是黑色，而是与背景同样的颜色，显得不好看。

显示效果：