QEventLoop

Qt 5.9.0 Reference Documentation

QEventLoop Class

The QEventLoop class provides a means of entering and leaving an event loop. 更多...

头文件:	#include <QEventLoop>
qmake:	QT += core
基类:	QObject

所有的成员列表, 包括继承的成员

公有类型

enum	ProcessEventsFlag { AllEvents, ExcludeUserInputEvents, ExcludeSocketNotifiers, WaitForMoreEvents }
flags	ProcessEventsFlags

公有函数

	QEventLoop(QObject *parent = Q_NULLPTR)
	~QEventLoop()
int	exec(ProcessEventsFlags flags = AllEvents)
void	exit(int returnCode = 0)
bool	isRunning() const
bool	processEvents(ProcessEventsFlags flags = AllEvents)
void	processEvents(ProcessEventsFlags flags, int maxTime)
void	wakeUp()

重新实现的公有函数

virtual bool event(QEvent *event)

32 个公有函数继承自 QObject

公有槽函数

void	quit()

1 个公有槽函数继承自 QObject

其他继承的成员

1 个属性继承自 QObject
2 个信号继承自 QObject
11 个静态公有成员继承自 QObject
9 个受保护的函数继承自 QObject

详细描述

The QEventLoop class provides a means of entering and leaving an event loop.

At any time, you can create a QEventLoop object and call exec() on it to start a local event loop. From within the event loop, calling exit() will force exec() to return.

参见 QAbstractEventDispatcher.

成员类型

enum QEventLoop::ProcessEventsFlag
flags QEventLoop::ProcessEventsFlags

This enum controls the types of events processed by the processEvents() functions.

Constant	Value	Description
`QEventLoop::AllEvents`	`0x00`	All events. Note that DeferredDelete events are processed specially. See QObject::deleteLater() for more details.
`QEventLoop::ExcludeUserInputEvents`	`0x01`	Do not process user input events, such as ButtonPress and KeyPress. Note that the events are not discarded; they will be delivered the next time processEvents() is called without the ExcludeUserInputEvents flag.
`QEventLoop::ExcludeSocketNotifiers`	`0x02`	Do not process socket notifier events. Note that the events are not discarded; they will be delivered the next time processEvents() is called without the ExcludeSocketNotifiers flag.
`QEventLoop::WaitForMoreEvents`	`0x04`	Wait for events if no pending events are available.

The ProcessEventsFlags type is a typedef for QFlags<ProcessEventsFlag>. It stores an OR combination of ProcessEventsFlag values.

参见 processEvents().

成员函数

QEventLoop::QEventLoop(QObject **parent* = Q_NULLPTR)

Constructs an event loop object with the given parent.

QEventLoop::~QEventLoop()

Destroys the event loop object.

`[virtual]` bool QEventLoop::event(QEvent **event*)

Reimplemented from QObject::event().

int QEventLoop::exec(ProcessEventsFlags flags = AllEvents)

Enters the main event loop and waits until exit() is called. Returns the value that was passed to exit().

If flags are specified, only events of the types allowed by the flags will be processed.

It is necessary to call this function to start event handling. The main event loop receives events from the window system and dispatches these to the application widgets.

Generally speaking, no user interaction can take place before calling exec(). As a special case, modal widgets like QMessageBox can be used before calling exec(), because modal widgets use their own local event loop.

To make your application perform idle processing (i.e. executing a special function whenever there are no pending events), use a QTimer with 0 timeout. More sophisticated idle processing schemes can be achieved using processEvents().

参见 QCoreApplication::quit(), exit(), and processEvents().

void QEventLoop::exit(int returnCode = 0)

Tells the event loop to exit with a return code.

After this function has been called, the event loop returns from the call to exec(). The exec() function returns returnCode.

By convention, a returnCode of 0 means success, and any non-zero value indicates an error.

Note that unlike the C library function of the same name, this function does return to the caller -- it is event processing that stops.

参见 QCoreApplication::quit(), quit(), and exec().

bool QEventLoop::isRunning() const

Returns true if the event loop is running; otherwise returns false. The event loop is considered running from the time when exec() is called until exit() is called.

参见 exec() and exit().

bool QEventLoop::processEvents(ProcessEventsFlags flags = AllEvents)

Processes pending events that match flags until there are no more events to process. Returns true if pending events were handled; otherwise returns false.

This function is especially useful if you have a long running operation and want to show its progress without allowing user input; i.e. by using the ExcludeUserInputEvents flag.

This function is simply a wrapper for QAbstractEventDispatcher::processEvents(). See the documentation for that function for details.

void QEventLoop::processEvents(ProcessEventsFlags flags, int maxTime)

Process pending events that match flags for a maximum of maxTime milliseconds, or until there are no more events to process, whichever is shorter. This function is especially useful if you have a long running operation and want to show its progress without allowing user input, i.e. by using the ExcludeUserInputEvents flag.

Notes:

This function does not process events continuously; it returns after all available events are processed.
Specifying the WaitForMoreEvents flag makes no sense and will be ignored.

`[slot]` void QEventLoop::quit()

Tells the event loop to exit normally.

Same as exit(0).

参见 QCoreApplication::quit() and exit().

void QEventLoop::wakeUp()

Wakes up the event loop.

参见 QAbstractEventDispatcher::wakeUp().

目录