The QAbstractMessageHandler class provides a callback interface for handling messages. 更多...
| 头： | #include <QAbstractMessageHandler> |
| qmake: | QT += xmlpatterns |
| Since: | Qt 4.4 |
| 继承： | QObject |
| QAbstractMessageHandler (QObject * parent = Q_NULLPTR) | |
| virtual | ~QAbstractMessageHandler () |
| void | message (QtMsgType type , const QString & description , const QUrl & 标识符 = QUrl(), const QSourceLocation & sourceLocation = QSourceLocation()) |
| virtual void | handleMessage (QtMsgType type , const QString & description , const QUrl & 标识符 , const QSourceLocation & sourceLocation ) = 0 |
The QAbstractMessageHandler class provides a callback interface for handling messages.
QAbstractMessageHandler is an abstract base class that provides a callback interface for handling messages. For example, class QXmlQuery parses and runs an XQuery . When it detects a compile or runtime error, it generates an appropriate error message, but rather than output the message itself, it passes the message to the message () function of its QAbstractMessageHandler 。见 QXmlQuery::setMessageHandler ().
You create a message handler by subclassing QAbstractMessageHandler and implementing handleMessage (). You then pass a pointer to an instance of your subclass to any classes that must generate messages. The messages are sent to the message handler via the message () function, which forwards them to your handleMessge().
A single instance of QAbstractMessageHandler can be called on to handle messages from multiple sources. Hence, the content of a message, which is the description parameter passed to message () 和 handleMessage (), must be interpreted in light of the context that required the message to be sent. That context is specified by the 标识符 and sourceLocation parameters to message () handleMessage ().
构造 QAbstractMessageHandler 。 parent 被传递给 QObject base class constructor.
[虚拟]
QAbstractMessageHandler::
~QAbstractMessageHandler
()
Destructs this QAbstractMessageHandler .
[pure virtual protected]
void
QAbstractMessageHandler::
handleMessage
(
QtMsgType
type
, const
QString
&
description
, const
QUrl
&
标识符
, const
QSourceLocation
&
sourceLocation
)
This function must be implemented by the sub-class. message () will call this function, passing in its parameters, type , description , 标识符 and sourceLocation 未经修改。
This function can potentially be called from multiple threads. It's the reimplementation's responsibility to ensure thread safety.
Sends a message to this message handler. type is the kind of message being sent. description is the message content. The 标识符 is a URI that identifies the message and is the key to interpreting the other arguments.
Typically, this class is used for reporting errors, as is the case for QXmlQuery , which uses a QAbstractMessageHandler to report compile and runtime XQuery errors. Hence, using a QUrl as the message 标识符 is was inspired by the explanation of error handling in the XQuery language . Because the 标识符 is composed of a namespace URI and a local part, identifiers with the same local part are unique. The caller is responsible for ensuring that 标识符 is either a valid QUrl or a default constructed QUrl .
sourceLocation identifies a location in a resource (i.e., file or document) where the need for reporting a message was detected.
This function unconditionally calls handleMessage (), passing all its parameters unmodified.