Qt MediaPlayer按键触发音乐仅首次生效问题求助

希望实现用户按键时播放音乐的功能，但目前仅第一次按键时音乐能正常播放，后续按键无法触发播放，请求技术帮助。

用户提供的代码如下：

#include <QApplication>
#include <QGraphicsView>
#include <QMediaPlayer>
#include <QAudioOutput>
#include <QGraphicsRectItem>
#include <QGraphicsScene>
#include <QKeyEvent>
#include <QDebug>


class Rect : public QGraphicsRectItem
{
public:
    Rect()
    {
        player = new QMediaPlayer();
        output = new QAudioOutput();
        player->setAudioOutput(output);
        output->setVolume(50);
        player->setSource(QUrl("qrc:/sounds/gun.mp3"));
        player->play();
    }
    void keyPressEvent(QKeyEvent* ev)
    {
        player->play();
    }

private:
    QMediaPlayer* player;
    QAudioOutput* output;
};


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


    QGraphicsScene* scene= new QGraphicsScene();
    Rect* rect = new Rect();
    rect->setFlags(QGraphicsItem::ItemIsFocusable);
    rect->setFocus();
    rect->setRect(0, 0, 300, 400);
    scene->addItem(rect);
    QGraphicsView* view = new QGraphicsView(scene);
    view->show();



    return a.exec();

    delete view;
    delete scene;
    delete rect;
}

问题原因 #

QMediaPlayer播放完音频后会停在末尾位置，再次调用play()时若当前位置已到达音频结尾，不会触发重新播放。此外，构造函数中提前调用了play()，首次按键时音频可能尚未播放完毕能正常响应，但后续音频播放结束后，play()调用就不再生效。

解决方法 #

核心修复 #

每次按键触发播放前，将QMediaPlayer的播放位置重置到开头，确保每次按键都从音频起始点播放：

player->setPosition(0);
player->play();

额外优化 #

1. 内存泄漏修复：添加析构函数释放QMediaPlayer和QAudioOutput实例，避免内存泄漏。
2. 资源释放顺序调整：原代码中delete语句位于return a.exec();之后，永远不会执行，需调整到exec()调用之后。

修改后的完整代码 #

#include <QApplication>
#include <QGraphicsView>
#include <QMediaPlayer>
#include <QAudioOutput>
#include <QGraphicsRectItem>
#include <QGraphicsScene>
#include <QKeyEvent>
#include <QDebug>

class Rect : public QGraphicsRectItem
{
public:
    Rect()
    {
        player = new QMediaPlayer();
        output = new QAudioOutput();
        player->setAudioOutput(output);
        output->setVolume(50);
        player->setSource(QUrl("qrc:/sounds/gun.mp3"));
        // 若不需要构造时自动播放，可删除下面这行
        // player->play();
    }

    void keyPressEvent(QKeyEvent* ev)
    {
        // 重置播放位置到音频开头
        player->setPosition(0);
        // 触发播放
        player->play();
    }

    // 析构函数释放资源
    ~Rect()
    {
        delete player;
        delete output;
    }

private:
    QMediaPlayer* player;
    QAudioOutput* output;
};

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

    QGraphicsScene* scene= new QGraphicsScene();
    Rect* rect = new Rect();
    rect->setFlags(QGraphicsItem::ItemIsFocusable);
    rect->setFocus();
    rect->setRect(0, 0, 300, 400);
    scene->addItem(rect);
    QGraphicsView* view = new QGraphicsView(scene);
    view->show();

    int appResult = a.exec();

    // 按正确顺序释放资源
    delete rect;
    delete scene;
    delete view;

    return appResult;
}

内容的提问来源于stack exchange，提问作者Bobr