QGCCachedFileDownload Class Reference

#include <QGCCachedFileDownload.h>

Inheritance diagram for QGCCachedFileDownload:

Collaboration diagram for QGCCachedFileDownload:

Public Slots
bool	download (const QString &url, int maxCacheAgeSec)
bool	downloadPreferCache (const QString &url)
bool	downloadNoCache (const QString &url)
void	cancel ()
	Cancel current download.
void	clearCache ()
	Clear all cached files.
bool	removeFromCache (const QString &url)

Signals
void	progressChanged (qreal progress)
	Emitted when download progress changes.
void	runningChanged (bool running)
	Emitted when running state changes.
void	errorStringChanged (const QString &errorString)
	Emitted when error string changes.
void	urlChanged (const QUrl &url)
	Emitted when URL changes.
void	localPathChanged (const QString &localPath)
	Emitted when local path changes.
void	fromCacheChanged (bool fromCache)
	Emitted when fromCache state changes.
void	cacheDirectoryChanged (const QString &directory)
	Emitted when cache directory changes.
void	maxCacheSizeChanged (qint64 bytes)
	Emitted when max cache size changes.
void	cacheSizeChanged (qint64 bytes)
	Emitted when cache size changes.
void	finished (bool success, const QString &localPath, const QString &errorMessage, bool fromCache)
void	downloadProgress (qint64 bytesReceived, qint64 totalBytes)
	Emitted during download with byte counts.

Detailed Description

Cached file download with time-based expiration

Features:

• Downloads files with Qt's network disk cache
• Time-based cache expiration (configurable per-request)
• Automatic fallback to cached version on network failure
• Progress reporting
• QML-compatible properties

Cache behavior:

1. If cached file exists and is not expired → use cache immediately
2. If cached file exists but is expired → try network, fallback to cache on failure
3. If no cached file → download from network

Example C++ usage:

auto *downloader = new QGCCachedFileDownload("/path/to/cache", this);
connect(downloader, &QGCCachedFileDownload::finished, this,
        [](bool success, const QString &path, const QString &error, bool fromCache) {
    qDebug() << "Downloaded:" << path << "from cache:" << fromCache;
});
downloader->download("https://example.com/data.json", 3600);  // 1 hour cache

Example QML usage:

QGCCachedFileDownload {
    id: cachedDownloader
    cacheDirectory: StandardPaths.writableLocation(StandardPaths.CacheLocation)
    onFinished: (success, path, error, fromCache) => {
        console.log("Downloaded:", path, "cached:", fromCache)
    }
}
Button {
    text: cachedDownloader.running ? "Downloading..." : "Download"
    onClicked: cachedDownloader.download(urlField.text, 3600)
}

Definition at line 55 of file QGCCachedFileDownload.h.

Member Function Documentation

cacheDirectoryChanged

void QGCCachedFileDownload::cacheDirectoryChanged ( const QString &  directory )

signal

Emitted when cache directory changes.

cacheSizeChanged

void QGCCachedFileDownload::cacheSizeChanged ( qint64  bytes )

signal

Emitted when cache size changes.

Referenced by clearCache(), and removeFromCache().

cancel

void QGCCachedFileDownload::cancel ( )

slot

Cancel current download.

Definition at line 260 of file QGCCachedFileDownload.cc.

References QGCFileDownload::cancel().

clearCache

void QGCCachedFileDownload::clearCache ( )

slot

Clear all cached files.

Definition at line 283 of file QGCCachedFileDownload.cc.

References cacheSizeChanged().

download

bool QGCCachedFileDownload::download ( const QString &  url, int  maxCacheAgeSec  )

slot

Download a file with cache support

Parameters

url	URL to download
maxCacheAgeSec	Maximum cache age in seconds (0 = any age is valid)

Returns

true if download started successfully

Definition at line 147 of file QGCCachedFileDownload.cc.

References urlChanged().

Referenced by ComponentInformationTranslation::downloadAndTranslate().

downloadNoCache

bool QGCCachedFileDownload::downloadNoCache ( const QString &  url )

slot

Download a file, bypassing cache entirely

Parameters

url	URL to download

Returns

true if download started successfully

Definition at line 235 of file QGCCachedFileDownload.cc.

References urlChanged().

downloadPreferCache

bool QGCCachedFileDownload::downloadPreferCache ( const QString &  url )

slot

Download a file, always using cache if available (no expiration check)

Parameters

url	URL to download

Returns

true if download started successfully

Definition at line 204 of file QGCCachedFileDownload.cc.

References urlChanged().

downloadProgress

void QGCCachedFileDownload::downloadProgress ( qint64  bytesReceived, qint64  totalBytes  )

signal

Emitted during download with byte counts.

errorStringChanged

void QGCCachedFileDownload::errorStringChanged ( const QString &  errorString )

signal

Emitted when error string changes.

finished

void QGCCachedFileDownload::finished ( bool  success, const QString &  localPath, const QString &  errorMessage, bool  fromCache  )

signal

Emitted when download completes

Parameters

success	true if download succeeded
localPath	Path to downloaded/cached file
errorMessage	Error message (empty on success)
fromCache	true if result came from cache

Referenced by ComponentInformationTranslation::downloadAndTranslate().

fromCacheChanged

void QGCCachedFileDownload::fromCacheChanged ( bool  fromCache )

signal

Emitted when fromCache state changes.

localPathChanged

void QGCCachedFileDownload::localPathChanged ( const QString &  localPath )

signal

Emitted when local path changes.

maxCacheSizeChanged

void QGCCachedFileDownload::maxCacheSizeChanged ( qint64  bytes )

signal

Emitted when max cache size changes.

progressChanged

void QGCCachedFileDownload::progressChanged ( qreal  progress )

signal

Emitted when download progress changes.

removeFromCache

bool QGCCachedFileDownload::removeFromCache ( const QString &  url )

slot

Remove a specific URL from cache

Parameters

url	URL to remove

Returns

true if removed successfully

Definition at line 290 of file QGCCachedFileDownload.cc.

References cacheSizeChanged().

runningChanged

void QGCCachedFileDownload::runningChanged ( bool  running )

signal

Emitted when running state changes.

urlChanged

void QGCCachedFileDownload::urlChanged ( const QUrl &  url )

signal

Emitted when URL changes.

Referenced by download(), downloadNoCache(), and downloadPreferCache().

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The documentation for this class was generated from the following files:

• src/Utilities/FileSystem/QGCCachedFileDownload.h
• src/Utilities/FileSystem/QGCCachedFileDownload.cc