QNetworkDiskCache Class

  QNetworkAccessManager *manager = new QNetworkAccessManager(this);
  QNetworkDiskCache *diskCache = new QNetworkDiskCache(this);
  diskCache->setCacheDirectory("cacheDir");
  manager->setCache(diskCache);

  // do a normal request (preferred from network, as this is the default)
  QNetworkRequest request(QUrl(QString("http://qt-project.org")));
  manager->get(request);

  // do a request preferred from cache
  QNetworkRequest request2(QUrl(QString("http://qt-project.org")));
  request2.setAttribute(QNetworkRequest::CacheLoadControlAttribute, QNetworkRequest::PreferCache);
  manager->get(request2);

  void replyFinished(QNetworkReply *reply) {
      QVariant fromCache = reply->attribute(QNetworkRequest::SourceIsFromCacheAttribute);
      qDebug() << "page from cache?" << fromCache.toBool();
  }

成员函数

QNetworkDiskCache::QNetworkDiskCache(QObject *parent = Q_NULLPTR)

Creates a new disk cache. The parent argument is passed to QAbstractNetworkCache's constructor.

QNetworkDiskCache::~QNetworkDiskCache()

Destroys the cache object. This does not clear the disk cache.

QString QNetworkDiskCache::cacheDirectory() const

Returns the location where cached files will be stored.

参见 setCacheDirectory().

[virtual] qint64 QNetworkDiskCache::cacheSize() const

Reimplemented from QAbstractNetworkCache::cacheSize().

[virtual slot] void QNetworkDiskCache::clear()

Reimplemented from QAbstractNetworkCache::clear().

[virtual] QIODevice *QNetworkDiskCache::data(const QUrl &url)

Reimplemented from QAbstractNetworkCache::data().

[virtual protected] qint64 QNetworkDiskCache::expire()

Cleans the cache so that its size is under the maximum cache size. Returns the current size of the cache.

When the current size of the cache is greater than the maximumCacheSize() older cache files are removed until the total size is less then 90% of maximumCacheSize() starting with the oldest ones first using the file creation date to determine how old a cache file is.

Subclasses can reimplement this function to change the order that cache files are removed taking into account information in the application knows about that QNetworkDiskCache does not, for example the number of times a cache is accessed.

Note: cacheSize() calls expire if the current cache size is unknown.

参见 maximumCacheSize() and fileMetaData().

QNetworkCacheMetaData QNetworkDiskCache::fileMetaData(const QString &fileName) const

Returns the QNetworkCacheMetaData for the cache file fileName.

If fileName is not a cache file QNetworkCacheMetaData will be invalid.

[virtual] void QNetworkDiskCache::insert(QIODevice *device)

Reimplemented from QAbstractNetworkCache::insert().

qint64 QNetworkDiskCache::maximumCacheSize() const

Returns the current maximum size for the disk cache.

参见 setMaximumCacheSize().

[virtual] QNetworkCacheMetaData QNetworkDiskCache::metaData(const QUrl &url)

Reimplemented from QAbstractNetworkCache::metaData().

[virtual] QIODevice *QNetworkDiskCache::prepare(const QNetworkCacheMetaData &metaData)

Reimplemented from QAbstractNetworkCache::prepare().

[virtual] bool QNetworkDiskCache::remove(const QUrl &url)

Reimplemented from QAbstractNetworkCache::remove().

void QNetworkDiskCache::setCacheDirectory(const QString &cacheDir)

Sets the directory where cached files will be stored to cacheDir

QNetworkDiskCache will create this directory if it does not exists.

Prepared cache items will be stored in the new cache directory when they are inserted.

参见 cacheDirectory() and QDesktopServices::CacheLocation.

void QNetworkDiskCache::setMaximumCacheSize(qint64 size)

Sets the maximum size of the disk cache to be size.

If the new size is smaller then the current cache size then the cache will call expire().

参见 maximumCacheSize().

[virtual] void QNetworkDiskCache::updateMetaData(const QNetworkCacheMetaData &metaData)

Reimplemented from QAbstractNetworkCache::updateMetaData().