The QPluginLoader class loads a plugin at run-time. 更多...
| 頭： | #include <QPluginLoader> |
| qmake: | QT += core |
| 繼承： | QObject |
注意： 此類的所有函數 可重入 .
| QPluginLoader (QObject * parent = nullptr) | |
| QPluginLoader (const QString & fileName , QObject * parent = nullptr) | |
| virtual | ~QPluginLoader () |
| QString | errorString () const |
| QString | fileName () const |
| QObject * | instance () |
| bool | isLoaded () const |
| bool | load () |
| QLibrary::LoadHints | loadHints () const |
| QJsonObject | metaData () const |
| void | setFileName (const QString & fileName ) |
| void | setLoadHints (QLibrary::LoadHints loadHints ) |
| bool | unload () |
| QObjectList | staticInstances () |
| const QMetaObject | staticMetaObject |
| QVector<QStaticPlugin> | staticPlugins () |
| void | qRegisterStaticPluginFunction (QStaticPlugin plugin ) |
The QPluginLoader class loads a plugin at run-time.
QPluginLoader provides access to a Qt plugin 。Qt 插件存儲在 DLL 共享庫中並提供這些好處，相比訪問共享庫使用 QLibrary :
An instance of a QPluginLoader object operates on a single shared library file, which we call a plugin. It provides access to the functionality in the plugin in a platform-independent way. To specify which plugin to load, either pass a file name in the constructor or set it with setFileName ().
最重要功能是 load () 用於動態加載插件文件， isLoaded () 用於校驗加載是否成功，及 instance () 用於訪問插件中的根組件。 instance () function implicitly tries to load the plugin if it has not been loaded yet. Multiple instances of QPluginLoader can be used to access the same physical plugin.
Once loaded, plugins remain in memory until all instances of QPluginLoader has been unloaded, or until the application terminates. You can attempt to unload a plugin using unload (), but if other instances of QPluginLoader are using the same library, the call will fail, and unloading will only happen when every instance has called unload (). Right before the unloading happen, the root component will also be deleted.
見 如何創建 Qt 插件 for more information about how to make your application extensible through plugins.
注意， QPluginLoader cannot be used if your application is statically linked against Qt. In this case, you will also have to link to plugins statically. You can use QLibrary if you need to load dynamic libraries in a statically linked application.
此特性保持插件的文件名
We recommend omitting the file's suffix in the file name, since QPluginLoader will automatically look for the file with the appropriate suffix (see QLibrary::isLibrary ()).
When loading the plugin, QPluginLoader searches in the current directory and in all plugin locations specified by QCoreApplication::libraryPaths (), unless the file name has an absolute path. After loading the plugin successfully, fileName() returns the fully-qualified file name of the plugin, including the full path to the plugin if one was given in the constructor or passed to setFileName().
If the file name does not exist, it will not be set. This property will then contain an empty string.
默認情況下，此特性包含空字符串。
訪問函數：
| QString | fileName () const |
| void | setFileName (const QString & fileName ) |
另請參閱 load ().
Give the load () function some hints on how it should behave.
You can give hints on how the symbols in the plugin are resolved. By default since Qt 5.7, QLibrary::PreventUnloadHint 有設置。
See the documentation of QLibrary::loadHints for a complete description of how this property works.
該特性在 Qt 4.4 引入。
訪問函數：
| QLibrary::LoadHints | loadHints () const |
| void | setLoadHints (QLibrary::LoadHints loadHints ) |
另請參閱 QLibrary::loadHints .
構造插件加載器采用給定 parent .
構造插件加載器采用給定 parent 將加載指定插件通過 fileName .
要可加載，文件後綴必須是與平颱一緻的有效可加載庫後綴，如
.so
在 Unix，
.dylib
on
macOS
and iOS, and
.dll
在 Windows。可以驗證後綴采用
QLibrary::isLibrary
().
另請參閱 setFileName ().
[虛擬]
QPluginLoader::
~QPluginLoader
()
銷毀 QPluginLoader 對象。
除非 unload () was called explicitly, the plugin stays in memory until the application terminates.
Returns a text string with the description of the last error that occurred.
該函數在 Qt 4.2 引入。
返迴插件的根組件對象。插件被加載若有必要。函數返迴
nullptr
若插件無法被加載或根組件對象無法被實例化。
若根組件對象被銷毀，調用此函創建新實例。
不會刪除由此函數返迴的根組件當 QPluginLoader 被銷毀時。若想要確保刪除根組件，應該調用 unload () 隻要不再需要訪問核心組件。當庫被最終卸載時，將自動刪除根組件。
組件對象是 QObject 。使用 qobject_cast () 訪問感興趣接口。
另請參閱 load ().
返迴
true
若插件被加載；否則返迴
false
.
另請參閱 load ().
加載插件並返迴
true
若插件加載成功；否則返迴
false
。由於
instance
() always calls this function before resolving any symbols it is not necessary to call it explicitly. In some situations you might want the plugin loaded in advance, in which case you would use this function.
另請參閱 unload ().
Returns the meta data for this plugin. The meta data is data specified in a json format using the Q_PLUGIN_METADATA () macro when compiling the plugin.
The meta data can be queried in a fast and inexpensive way without actually loading the plugin. This makes it possible to e.g. store capabilities of the plugin in there, and make the decision whether to load the plugin dependent on this meta data.
[static]
QObjectList
QPluginLoader::
staticInstances
()
Returns a list of static plugin instances (root components) held by the plugin loader.
另請參閱 staticPlugins ().
[static]
QVector
<
QStaticPlugin
> QPluginLoader::
staticPlugins
()
Returns a list of QStaticPlugins held by the plugin loader. The function is similar to staticInstances () with the addition that a QStaticPlugin also contains meta data information.
另請參閱 staticInstances ().
卸載插件並返迴
true
若插件可以被卸載；否則返迴
false
.
This happens automatically on application termination, so you shouldn't normally need to call this function.
If other instances of QPluginLoader are using the same plugin, the call will fail, and unloading will only happen when every instance has called unload().
Don't try to delete the root component. Instead rely on that unload() will automatically delete it when needed.
注冊 plugin 指定采用插件加載器，並用於 Q_IMPORT_PLUGIN ().
該函數在 Qt 5.0 引入。