The QMimeDatabase class maintains a database of MIME types. 更多...
| 头： | #include <QMimeDatabase> |
| qmake: | QT += core |
| Since: | Qt 5.0 |
注意： 此类的所有函数 thread-safe .
| enum | MatchMode { MatchDefault, MatchExtension, MatchContent } |
| QMimeDatabase () | |
| ~QMimeDatabase () | |
| QList<QMimeType> | allMimeTypes () const |
| QMimeType | mimeTypeForData (const QByteArray & data ) const |
| QMimeType | mimeTypeForData (QIODevice * device ) const |
| QMimeType | mimeTypeForFile (const QFileInfo & fileInfo , MatchMode mode = MatchDefault) const |
| QMimeType | mimeTypeForFile (const QString & fileName , MatchMode mode = MatchDefault) const |
| QMimeType | mimeTypeForFileNameAndData (const QString & fileName , QIODevice * device ) const |
| QMimeType | mimeTypeForFileNameAndData (const QString & fileName , const QByteArray & data ) const |
| QMimeType | mimeTypeForName (const QString & nameOrAlias ) const |
| QMimeType | mimeTypeForUrl (const QUrl & url ) const |
| QList<QMimeType> | mimeTypesForFileName (const QString & fileName ) const |
| QString | suffixForFileName (const QString & fileName ) const |
The QMimeDatabase class maintains a database of MIME types.
The MIME type database is provided by the freedesktop.org shared-mime-info project. If the MIME type database cannot be found on the system, as is the case on most Windows, macOS, and iOS systems, Qt will use its own copy of it.
Applications which want to define custom MIME types need to install an XML file into the locations searched for MIME definitions. These locations can be queried with
QStandardPaths::locateAll(QStandardPaths::GenericDataLocation, QLatin1String("mime/packages"), QStandardPaths::LocateDirectory);
On a typical Unix system, this will be /usr/share/mime/packages/, but it is also possible to extend the list of directories by setting the environment variable
XDG_DATA_DIRS
. For instance adding /opt/myapp/share to
XDG_DATA_DIRS
will result in /opt/myapp/share/mime/packages/ being searched for MIME definitions.
Here is an example of MIME XML:
<?xml version="1.0" encoding="UTF-8"?> <mime-info xmlns="http://www.freedesktop.org/standards/shared-mime-info"> <mime-type type="application/vnd.qt.qmakeprofile"> <comment xml:lang="en">Qt qmake Profile</comment> <glob pattern="*.pro" weight="50"/> </mime-type> </mime-info>
For more details about the syntax of XML MIME definitions, including defining "magic" in order to detect MIME types based on data as well, read the Shared Mime Info specification at http://standards.freedesktop.org/shared-mime-info-spec/shared-mime-info-spec-latest.html
On Unix systems, a binary cache is used for more performance. This cache is generated by the command "update-mime-database path", where path would be /opt/myapp/share/mime in the above example. Make sure to run this command when installing the MIME type definition file.
QMimeDatabase db; QMimeType mime = db.mimeTypeForFile(fileName); if (mime.inherits("text/plain")) { // The file is plain text, we can display it in a QTextEdit }
另请参阅 QMimeType and MIME 类型浏览器范例 .
This enum specifies how matching a file to a MIME type is performed.
| 常量 | 值 | 描述 |
|---|---|---|
QMimeDatabase::MatchDefault
|
0x0
|
Both the file name and content are used to look for a match |
QMimeDatabase::MatchExtension
|
0x1
|
Only the file name is used to look for a match |
QMimeDatabase::MatchContent
|
0x2
|
The file content is used to look for a match |
构造 QMimeDatabase 对象。
It is perfectly OK to create an instance of QMimeDatabase every time you need to perform a lookup. The parsing of mimetypes is done on demand (when shared-mime-info is installed) or when the very first instance is constructed (when parsing XML files directly).
销毁 QMimeDatabase 对象。
Returns the list of all available MIME types.
This can be useful for showing all MIME types to the user, for instance in a MIME type editor. Do not use unless really necessary in other cases though, prefer using the mimeTypeForXxx() methods for performance reasons.
返回 MIME 类型为 data .
A valid MIME type is always returned. If data doesn't match any known MIME type data, the default MIME type (application/octet-stream) is returned.
Returns a MIME type for the data in device .
A valid MIME type is always returned. If the data in device doesn't match any known MIME type data, the default MIME type (application/octet-stream) is returned.
返回 MIME 类型为 fileInfo .
A valid MIME type is always returned.
The default matching algorithm looks at both the file name and the file contents, if necessary. The file extension has priority over the contents, but the contents will be used if the file extension is unknown, or matches multiple MIME types. If fileInfo is a Unix symbolic link, the file that it refers to will be used instead. If the file doesn't match any known pattern or data, the default MIME type (application/octet-stream) is returned.
当 mode 被设为 MatchExtension , only the file name is used, not the file contents. The file doesn't even have to exist. If the file name doesn't match any known pattern, the default MIME type (application/octet-stream) is returned. If multiple MIME types match this file, the first one (alphabetically) is returned.
当 mode 被设为 MatchContent , and the file is readable, only the file contents are used to determine the MIME type. This is equivalent to calling mimeTypeForData 采用 QFile as input device.
fileInfo may refer to an absolute or relative path.
另请参阅 QMimeType::isDefault () 和 mimeTypeForData ().
Returns a MIME type for the file named fileName 使用 mode .
这是重载函数。
Returns a MIME type for the given fileName and device data.
This overload can be useful when the file is remote, and we started to download some of its data in a device. This allows to do full MIME type matching for remote files as well.
If the device is not open, it will be opened by this function, and closed after the MIME type detection is completed.
A valid MIME type is always returned. If device data doesn't match any known MIME type data, the default MIME type (application/octet-stream) is returned.
This method looks at both the file name and the file contents, if necessary. The file extension has priority over the contents, but the contents will be used if the file extension is unknown, or matches multiple MIME types.
Returns a MIME type for the given fileName and device data .
This overload can be useful when the file is remote, and we started to download some of its data. This allows to do full MIME type matching for remote files as well.
A valid MIME type is always returned. If data doesn't match any known MIME type data, the default MIME type (application/octet-stream) is returned.
This method looks at both the file name and the file contents, if necessary. The file extension has priority over the contents, but the contents will be used if the file extension is unknown, or matches multiple MIME types.
返回 MIME 类型为 nameOrAlias or an invalid one if none found.
返回 MIME 类型为 url .
若 URL 是本地文件，这调用 mimeTypeForFile .
Otherwise the matching is done based on the file name only, except for schemes where file names don't mean much, like HTTP. This method always returns the default mimetype for HTTP URLs, use QNetworkAccessManager to handle HTTP URLs properly.
A valid MIME type is always returned. If url doesn't match any known MIME type data, the default MIME type (application/octet-stream) is returned.
Returns the MIME types for the file name fileName .
If the file name doesn't match any known pattern, an empty list is returned. If multiple MIME types match this file, they are all returned.
This function does not try to open the file. To also use the content when determining the MIME type, use mimeTypeForFile () 或 mimeTypeForFileNameAndData () 代替。
另请参阅 mimeTypeForFile ().
Returns the suffix for the file fileName , as known by the MIME database.
This allows to pre-select "tar.bz2" for foo.tar.bz2, but still only "txt" for my.file.with.dots.txt.
