Qt4 音乐声音控件问题 大神助我。

[QiuZhaoHai]

控件没显示出来在界面。。。
.h文件
#ifndef MEDIAPLAYER_H
#define MEDIAPLAYER_H
#include <phonon/MediaObject>
#include <phonon/VideoPlayer>
#include <phonon/AudioOutput>
#include <phonon/BackendCapabilities>
#include <phonon/volumeslider>
#include <QGridLayout>
#include <QUrl>
class MediaPlayer:public QWidget
{
Q_OBJECT
public:
MediaPlayer(QString Path);
public slots:
void finished();
private:
Phonon::AudioOutput * AudioOut;
Phonon::MediaObject * MediaObj;
Phonon::VolumeSlider *volumeSlider;
QString Path;
};

#endif // MEDIAPLAYER_H

.c文件
#include "mediaplayer.h"

MediaPlayer::MediaPlayer(QString Path)
{
this->Path=Path;
AudioOut=new Phonon::AudioOutput(Phonon::MusicCategory,this);
MediaObj=new Phonon::MediaObject(this);
Phonon::createPath(MediaObj,AudioOut);
QUrl Url(this->Path);
MediaObj->setCurrentSource(Url);
connect(MediaObj, SIGNAL(finished()), SLOT(finished()));
MediaObj->play();
volumeSlider = new Phonon::VolumeSlider(this);
volumeSlider->setAudioOutput(AudioOut);
volumeSlider->setStyleSheet("VolumeSlider{background-color: rgba(255,255,255);}");//设置音量条背景色
volumeSlider->setGeometry(20,490,100,20);
volumeSlider->setFixedWidth(20);//固定音量条长度
volumeSlider->setSizePolicy(QSizePolicy::Maximum, QSizePolicy::Maximum);
QHBoxLayout *volumeLayout = new QHBoxLayout();
volumeLayout->addWidget(volumeSlider);
}

void MediaPlayer::finished()
{
QUrl url(this->Path);
MediaObj->setCurrentSource(url);
MediaObj->play();
}

[QiuZhaoHai]

已解决，没加show。。。