Got it, let's walk through how to build this update checker in Qt C++. We'll use Qt's network tools to talk to GitHub's API, parse the release data, compare versions, and handle the file download. Here's a step-by-step breakdown with code snippets you can adapt:

First, make sure your .pro file includes the Network module—we need it for all the network requests:

QT += core gui network

GitHub provides a REST API endpoint to get the latest release for any repository: https://api.github.com/repos/{owner}/{repo}/releases/latest. We'll use QNetworkAccessManager to send a GET request and process the JSON response.

Here's a sample Updater class with core functionality:

#include <QNetworkAccessManager>
#include <QNetworkRequest>
#include <QNetworkReply>
#include <QJsonDocument>
#include <QJsonObject>
#include <QJsonArray>
#include <QFile>
#include <QDebug>
#include <QRegExp>

class Updater : public QObject
{
    Q_OBJECT
public:
    explicit Updater(QObject *parent = nullptr) : QObject(parent), m_localVersion("1.0.0") {} // Replace with your app's current version

    // Trigger the update check
    void checkForUpdates() {
        QNetworkAccessManager *manager = new QNetworkAccessManager(this);
        connect(manager, &QNetworkAccessManager::finished, this, &Updater::onLatestReleaseReceived);

        // Replace {owner} and {repo} with your target repository details
        QUrl apiUrl("https://api.github.com/repos/{owner}/{repo}/releases/latest");
        QNetworkRequest request(apiUrl);
        // GitHub requires a User-Agent header to avoid rate-limiting
        request.setRawHeader("User-Agent", "Qt-App-Update-Checker");
        manager->get(request);
    }

private slots:
    // Handle the API response for latest release
    void onLatestReleaseReceived(QNetworkReply *reply) {
        if (reply->error() != QNetworkReply::NoError) {
            qDebug() << "Failed to fetch latest release:" << reply->errorString();
            reply->deleteLater();
            return;
        }

        // Parse the JSON response
        QByteArray responseData = reply->readAll();
        QJsonDocument jsonDoc = QJsonDocument::fromJson(responseData);
        if (!jsonDoc.isObject()) {
            qDebug() << "Invalid JSON response from GitHub API";
            reply->deleteLater();
            return;
        }

        QJsonObject releaseObj = jsonDoc.object();
        QString latestVersion = releaseObj["tag_name"].toString(); // e.g., "v1.1.0"

        // Check if the remote version is newer than local
        if (isVersionNewer(latestVersion, m_localVersion)) {
            qDebug() << "New update available:" << latestVersion;
            // Grab the download URL for your target asset (adjust if you have multiple assets)
            QJsonArray assets = releaseObj["assets"].toArray();
            if (!assets.isEmpty()) {
                QJsonObject asset = assets.first().toObject();
                QString downloadUrl = asset["browser_download_url"].toString();
                downloadUpdateFile(downloadUrl);
            }
        } else {
            qDebug() << "You're already running the latest version:" << m_localVersion;
        }

        reply->deleteLater();
    }

    // Start downloading the update file
    void downloadUpdateFile(const QString &downloadUrl) {
        QNetworkAccessManager *manager = new QNetworkAccessManager(this);
        connect(manager, &QNetworkAccessManager::finished, this, &Updater::onFileDownloaded);

        QNetworkRequest request(QUrl(downloadUrl));
        manager->get(request);
    }

    // Handle completed download
    void onFileDownloaded(QNetworkReply *reply) {
        if (reply->error() != QNetworkReply::NoError) {
            qDebug() << "Download failed:" << reply->errorString();
            reply->deleteLater();
            return;
        }

        // Save the file to your desired location (adjust path as needed)
        QFile updateFile("./update.zip");
        if (updateFile.open(QIODevice::WriteOnly)) {
            updateFile.write(reply->readAll());
            updateFile.close();
            qDebug() << "Update file saved successfully!";
            // Add logic here to notify the user or initiate installation
        } else {
            qDebug() << "Could not open file for writing:" << updateFile.errorString();
        }

        reply->deleteLater();
    }

    // Compare two version strings (handles prefixes like "v")
    bool isVersionNewer(const QString &latestVersion, const QString &localVersion) {
        // Clean version strings by removing leading "v" or whitespace
        QString cleanLatest = latestVersion.trimmed().remove(QRegExp("^v"));
        QString cleanLocal = localVersion.trimmed().remove(QRegExp("^v"));

        // Split into numeric components
        QStringList latestParts = cleanLatest.split(".", Qt::SkipEmptyParts);
        QStringList localParts = cleanLocal.split(".", Qt::SkipEmptyParts);

        int maxParts = qMax(latestParts.size(), localParts.size());
        for (int i = 0; i < maxParts; ++i) {
            int latestNum = (i < latestParts.size()) ? latestParts[i].toInt() : 0;
            int localNum = (i < localParts.size()) ? localParts[i].toInt() : 0;

            if (latestNum > localNum) return true;
            if (latestNum < localNum) return false;
        }
        // Versions are identical
        return false;
    }

private:
    QString m_localVersion; // Store your app's current version here
};

• User-Agent Header: Don't skip this—GitHub's API requires it to identify your request, and you might get rate-limited or blocked without it.
• Version Comparison: The isVersionNewer function handles basic semantic versioning. If you need to support pre-release tags (like v1.1.0-beta), you'll need to extend this logic to parse and compare those suffixes.
• Download Progress: To add a progress bar, connect to QNetworkReply::downloadProgress(qint64 bytesReceived, qint64 bytesTotal) and update your UI accordingly.
• User Feedback: Replace qDebug messages with user-facing dialogs or notifications to keep your users informed about update status.
• File Permissions: Ensure your app has write access to the directory where you're saving the update file.
• Asynchronous Flow: All Qt network calls are asynchronous, so your UI won't freeze while checking for updates or downloading files.

内容的提问来源于stack exchange，提问作者Alberto Valero