下载完成后带result的QT回调

#include <QCoreApplication>
#include <QNetworkAccessManager>
#include <QNetworkReply>
#include <QFile>

class Downloader : public QObject
{
    Q_OBJECT
public:
    explicit Downloader(QObject *parent = nullptr) : QObject(parent) {}

    void downloadFile(const QUrl& url)
    {
        QNetworkAccessManager* manager = new QNetworkAccessManager(this);
        QNetworkReply* reply = manager->get(QNetworkRequest(url));

        connect(reply, &QNetworkReply::finished, this, &Downloader::onDownloadFinished);
    }

private slots:
    void onDownloadFinished()
    {
        QNetworkReply* reply = qobject_cast<QNetworkReply*>(sender());
        if (reply->error() == QNetworkReply::NoError)
        {
            // 下载成功
            QByteArray data = reply->readAll();
            // 处理下载的数据

            // 调用回调函数，将下载结果返回给应用程序
            handleDownloadResult(true, data);
        }
        else
        {
            // 下载失败
            handleDownloadResult(false, QByteArray());
        }

        reply->deleteLater();
    }

signals:
    void handleDownloadResult(bool success, const QByteArray& data);
};

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

    Downloader downloader;
    QObject::connect(&downloader, &Downloader::handleDownloadResult, [](bool success, const QByteArray& data) {
        if (success)
        {
            // 下载成功，处理数据
            qDebug() << "Download success. Data size: " << data.size();
        }
        else
        {
            // 下载失败
            qDebug() << "Download failed.";
        }

        // 在这里进行后续处理
        // ...
        
        // 退出应用程序
        QCoreApplication::quit();
    });

    QUrl url("http://example.com/file.txt");
    downloader.downloadFile(url);

    return a.exec();
}

#include "main.moc"