用Qt写一个简单的音乐播放器（六）：显示歌词（正则表达式）

一、前言

在用Qt写一个简单的音乐播放器（一）：使用QMediaPlayer播放音乐中，我们已经知道如何去使用QMediaPlayer播放音乐。
在用Qt写一个简单的音乐播放器（二）：增加界面（开始和暂停音乐)中，我们增加了播放音乐/暂停音乐的按钮。
在用Qt写一个简单的音乐播放器（三）：增加界面（播放跳转与音量控制）中，我们加入了播放控制和音量控制。
在用Qt写一个简单的音乐播放器（四）：歌曲浏览、上一曲、下一曲中，我们增加了歌曲选择的功能。
在用Qt写一个简单的音乐播放器（五）：歌曲播放时间显示中，我们为歌曲播放增加播放时间显示。
那么第六篇文章来谈一谈如何显示歌词：

二、读取歌词文件

如图所示，首先将同名的歌词文件放入歌曲相同的路径中。

如上图所示，歌词文件的内容形式为一行一句，所以我们可以将歌词文件逐行读入，代码如下。
mainwindow.cpp中做如下修改

void MainWindow::on_lwMusicList_itemDoubleClicked(QListWidgetItem *item)
{m_PlayRow = ui->lwMusicList->row(item);m_mediaPlayer.stop();m_mediaPlayer.setMedia(QUrl::fromLocalFile(m_playPath+"/"+item->text()));m_mediaPlayer.play();QString name = item->text().left(item->text().lastIndexOf("."));if(!lyrics.readLyricsFile(m_playPath+"/"+name+".lrc")){ui->lblLyrics1->setText("未检测到歌词文件");ui->lblLyrics2->setText("请检查歌词文件是否存在");}lyricsID = 0;ui->hSliderPlayProgress->setValue(m_mediaPlayer.position());ui->btnPlay->setText("Pause");connect(timer, SIGNAL(timeout()), this, SLOT(setSliderValue()));connect(&m_mediaPlayer,SIGNAL(durationChanged(qint64)),this,SLOT(getduration()));connect(&m_mediaPlayer,SIGNAL(positionChanged(qint64)),this,SLOT(setPlayTime()));
}

新建一个lyrics类文件，加入以下代码：

bool Lyrics::readLyricsFile(QString lyricsPath)
{QFile file(lyricsPath);file.open(QIODevice::ReadOnly | QIODevice::Text);QString line="";while((line=file.readLine())>0){qDebug()<<line;analysisLyricsFile(line);//解析歌词文件内容}return true;
}

三、解析歌词（正则表达式的使用）

歌词读取一行，我们就对这个歌词进行解析。我这里将歌词分为了两部分：时间和内容。用正则表达式匹配后，将时间计算为毫秒存入listLyricsTime，将内容存入listLyricsText。

bool Lyrics::analysisLyricsFile(QString line)
{if(line == NULL || line.isEmpty()){qDebug()<<"thie line is empty!";return false;}QRegularExpression regularExpression("\\[(\\d+)?:(\\d+)?(\\.\\d+)?\\](.*)?");int index = 0;QRegularExpressionMatch match;match = regularExpression.match(line, index);if(match.hasMatch()) {int totalTime;totalTime = match.captured(1).toInt() * 60000 + match.captured(2).toInt() * 1000;                    /*  计算该时间点毫秒数            */QString currentText =QString::fromStdString(match.captured(4).toStdString());      /*   获取歌词文本*/listLyricsText.push_back(currentText);listLyricsTime.push_back(totalTime);return true;}return false;
}

四、歌词显示

1.控件

如图所示：拖两个label，一个用来显示播放当前歌词（设置为左对齐），一个用来显示下一句歌词（设置为右对齐）。

2.代码

在播放时间改变的时候，判断当前音乐的播放时间，是否大于歌词时间，若大于，则显示歌词。代码如下：

void MainWindow::setPlayTime()
{if(!lyrics.getListLyricsTime().empty()&&m_mediaPlayer.position()>=lyrics.getListLyricsTime().at(lyricsID)){ui->lblLyrics1->setText(lyrics.getListLyricsText().at(lyricsID));ui->lblLyrics2->setText(lyrics.getListLyricsText().at(lyricsID+1));lyricsID++;}ui->lblPlayTime->setText(settime(m_mediaPlayer.position()));
}

五、效果

六、完整代码

当然这个完整也只是相对完整，不过这个基本已经很全了。

1.歌词类

Lyrics.cpp

#include "lyrics.h"QList<QString> Lyrics::getListLyricsText() const
{return listLyricsText;
}QList<int> Lyrics::getListLyricsTime() const
{return listLyricsTime;
}Lyrics::Lyrics(QString lyricsPath)
{this->lyricsPath = lyricsPath;
}
Lyrics::Lyrics()
{}bool Lyrics::readLyricsFile(QString lyricsPath)
{QFile file(lyricsPath);if(!file.open(QIODevice::ReadOnly | QIODevice::Text)){listLyricsText.clear();listLyricsTime.clear();return false;}QString line="";while((line=file.readLine())>0){qDebug()<<line;analysisLyricsFile(line);}return true;
}bool Lyrics::analysisLyricsFile(QString line)
{if(line == NULL || line.isEmpty()){qDebug()<<"thie line is empty!";return false;}QRegularExpression regularExpression("\\[(\\d+)?:(\\d+)?(\\.\\d+)?\\](.*)?");int index = 0;QRegularExpressionMatch match;match = regularExpression.match(line, index);if(match.hasMatch()) {int totalTime;totalTime = match.captured(1).toInt() * 60000 + match.captured(2).toInt() * 1000;                    /*  计算该时间点毫秒数            */QString currentText =QString::fromStdString(match.captured(4).toStdString());      /*   获取歌词文本*/qDebug()<<totalTime;qDebug()<<currentText;listLyricsText.push_back(currentText);listLyricsTime.push_back(totalTime);return true;}return false;
}

lyrics.h

#ifndef LYRICS_H
#define LYRICS_H#include <QWidget>
#include <QString>
#include <QMap>
#include <iostream>
#include <QFile>
#include <QDebug>
#include <QRegExp>
#include <QList>
#include <QRegularExpression>
#include <QRegularExpressionMatch>
using namespace std;
class Lyrics
{private:QString lyricsPath;QList<QString> listLyricsText;QList<int> listLyricsTime;
public:Lyrics(QString lyricsPath);Lyrics();bool readLyricsFile(QString lyricsPath);bool analysisLyricsFile(QString line);QList<QString> getListLyricsText() const;QList<int> getListLyricsTime() const;
};#endif // LYRICS_H

2.mainwindow

mainwindow.cpp

#include "mainwindow.h"
#include "ui_mainwindow.h"MainWindow::MainWindow(QWidget *parent) :QMainWindow(parent),ui(new Ui::MainWindow)
{ui->setupUi(this);timer = new QTimer();timer->setInterval(2000);timer->start();ui->vSliderVolume->setVisible(false);QString fileName = "D:/music";QDir dir(fileName);QStringList nameFilters;nameFilters << "*.mp3";QStringList files = dir.entryList(nameFilters, QDir::Files|QDir::Readable, QDir::Name);ui->lwMusicList->addItems(files);m_playPath = fileName;
}MainWindow::~MainWindow()
{delete ui;
}void MainWindow::on_btnPlay_clicked()
{if(QMediaPlayer:: PlayingState == m_mediaPlayer.state()){m_mediaPlayer.pause();ui->btnPlay->setText("Play");}else{m_mediaPlayer.play();ui->btnPlay->setText("Pause");}
}void MainWindow::on_hSliderPlayProgress_sliderMoved(int position)
{m_mediaPlayer.setPosition(m_mediaPlayer.duration()*position/100);
}
void MainWindow::setSliderValue()
{ui->hSliderPlayProgress->setValue(m_mediaPlayer.position()*100/m_mediaPlayer.duration());if(m_mediaPlayer.position()>=m_mediaPlayer.duration()){on_btnNextMusic_clicked();}
}void MainWindow::on_vSliderVolume_sliderMoved(int position)
{m_mediaPlayer.setVolume(position);
}void MainWindow::on_lwMusicList_itemDoubleClicked(QListWidgetItem *item)
{m_PlayRow = ui->lwMusicList->row(item);m_mediaPlayer.stop();m_mediaPlayer.setMedia(QUrl::fromLocalFile(m_playPath+"/"+item->text()));m_mediaPlayer.play();QString name = item->text().left(item->text().lastIndexOf("."));if(!lyrics.readLyricsFile(m_playPath+"/"+name+".lrc")){ui->lblLyrics1->setText("未检测到歌词文件");ui->lblLyrics2->setText("请检查歌词文件是否存在");}lyricsID = 0;ui->hSliderPlayProgress->setValue(m_mediaPlayer.position());ui->btnPlay->setText("Pause");connect(timer, SIGNAL(timeout()), this, SLOT(setSliderValue()));connect(&m_mediaPlayer,SIGNAL(durationChanged(qint64)),this,SLOT(getduration()));connect(&m_mediaPlayer,SIGNAL(positionChanged(qint64)),this,SLOT(setPlayTime()));
}void MainWindow::on_btnAddMusic_clicked()
{QString fileName = QFileDialog::getExistingDirectory(NULL,"Select Music Dir",".",NULL);QDir dir(fileName);QStringList nameFilters;nameFilters << "*.mp3";QStringList files = dir.entryList(nameFilters, QDir::Files|QDir::Readable, QDir::Name);ui->lwMusicList->addItems(files);m_playPath = fileName;
}void MainWindow::on_btnPreMusic_clicked()
{if(m_PlayRow == 0){m_PlayRow = ui->lwMusicList->count() - 1;}else{m_PlayRow--;}QListWidgetItem *item = ui->lwMusicList->item(m_PlayRow);item->setSelected(true);m_mediaPlayer.stop();m_mediaPlayer.setMedia(QUrl::fromLocalFile(m_playPath+"/"+item->text()));m_mediaPlayer.play();
}void MainWindow::on_btnNextMusic_clicked()
{if(m_PlayRow + 1 == ui->lwMusicList->count()){m_PlayRow = 0;}else{m_PlayRow++;}QListWidgetItem *item = ui->lwMusicList->item(m_PlayRow);item->setSelected(true);m_mediaPlayer.stop();m_mediaPlayer.setMedia(QUrl::fromLocalFile(m_playPath+"/"+item->text()));m_mediaPlayer.play();
}void MainWindow::on_btnVolume_clicked()
{if(ui->vSliderVolume->isVisible()){ui->vSliderVolume->setVisible(false);}else{ui->vSliderVolume->setVisible(true);}
}void MainWindow::on_vSliderVolume_sliderReleased()
{ui->vSliderVolume->setVisible(false);
}
QString MainWindow::settime(int time)
{int h,m,s;time /= 1000;  //获得的时间是以毫秒为单位的h = time/3600;m = (time-h*3600)/60;s = time-h*3600-m*60;return QString("%1:%2:%3").arg(h).arg(m).arg(s);
}void MainWindow::getduration()
{playtime = m_mediaPlayer.duration();ui->lblMusicTime->setText(settime(playtime));
}
void MainWindow::setPlayTime()
{if(!lyrics.getListLyricsTime().empty()&&m_mediaPlayer.position()>=lyrics.getListLyricsTime().at(lyricsID)&&lyricsID<lyrics.getListLyricsTime().size()-1){ui->lblLyrics1->setText(lyrics.getListLyricsText().at(lyricsID));ui->lblLyrics2->setText(lyrics.getListLyricsText().at(lyricsID+1));lyricsID++;}ui->lblPlayTime->setText(settime(m_mediaPlayer.position()));
}

mainwindow.h

#ifndef MAINWINDOW_H
#define MAINWINDOW_H#include <QMainWindow>
#include <QtMultimedia/QMediaPlayer> // 包含头文件
#include <QTimer>
#include <QListWidgetItem>
#include <QString>
#include <QFileDialog>
#include <lyrics.h>
namespace Ui {class MainWindow;
}class MainWindow : public QMainWindow
{Q_OBJECTpublic:explicit MainWindow(QWidget *parent = 0);~MainWindow();QString settime(int time);private slots:void on_btnPlay_clicked();void on_hSliderPlayProgress_sliderMoved(int position);void setSliderValue();void on_vSliderVolume_sliderMoved(int position);void on_lwMusicList_itemDoubleClicked(QListWidgetItem *item);void on_btnAddMusic_clicked();void on_btnPreMusic_clicked();void on_btnNextMusic_clicked();void on_btnVolume_clicked();void on_vSliderVolume_sliderReleased();void getduration();void setPlayTime();private:Ui::MainWindow *ui;QMediaPlayer m_mediaPlayer; // 实例化对象QTimer *timer; //定时器QString m_playPath;Lyrics lyrics;int m_PlayRow;int playtime;int lyricsID = 0;
};#endif // MAINWINDOW_H

七、最后

从无到有，从最开始的播放音乐、开始、暂停、播放时间、跳转播放、音量控制、选择歌曲，到今天的歌词显示，一个简单的本地音乐播放器也终于写完了。当然它很丑，但是至少也是基本的功能也都有不是，剩下的界面美化啊，网络播放啊，等等功能吧，以后慢慢优化吧，当然现在这个代码也是有一定问题的，bug不少，代码结构也不好，以后功能越来越多的时候，肯定是要重构的。
用Qt写一个简单的音乐播放器（七）：界面美化（QSS样式表）