Qt 4.8: QKeyEvent Class Reference

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# QKeyEvent Class Reference

The QKeyEvent class describes a key event. More...

     #include <QKeyEvent>

Inherits: QInputEvent.

- List of all members, including inherited members
- Qt 3 support members

## Public Functions

| QKeyEvent ( Type type, int key, Qt::KeyboardModifiers modifiers, const QString & text = QString(), bool autorep = false, ushort count = 1 )
int | count () const
bool | isAutoRepeat () const
int | key () const
bool | matches ( QKeySequence::StandardKey key ) const
Qt::KeyboardModifiers | modifiers () const
quint32 | nativeModifiers () const
quint32 | nativeScanCode () const
quint32 | nativeVirtualKey () const
QString | text () const

- 1 public function inherited from QInputEvent
- 6 public functions inherited from QEvent

## Related Non-Members

bool | operator== ( QKeySequence::StandardKey key, QKeyEvent * e )
bool | operator== ( QKeyEvent * e, QKeySequence::StandardKey key )

### Additional Inherited Members

- 1 property inherited from QEvent
- 1 static public member inherited from QEvent

## Detailed Description

The QKeyEvent class describes a key event.

Key events are sent to the widget with keyboard input focus when keys are pressed or released.

A key event contains a special accept flag that indicates whether the receiver will handle the key event. You should call ignore() if the key press or release event is not handled by your widget. A key event is propagated up the parent widget chain until a widget accepts it with accept() or an event filter consumes it. Key events for multimedia keys are ignored by default. You should call accept() if your widget handles those events.

The QWidget::setEnable() function can be used to enable or disable mouse and keyboard events for a widget.

The event handlers QWidget::keyPressEvent(), QWidget::keyReleaseEvent(), QGraphicsItem::keyPressEvent() and QGraphicsItem::keyReleaseEvent() receive key events.

See also QFocusEvent and QWidget::grabKeyboard().

## Member Function Documentation

### QKeyEvent::QKeyEvent ( Type type, int key, Qt::KeyboardModifiers modifiers, const QString & text = QString(), bool autorep = false, ushort count = 1 )

Constructs a key event object.

The type parameter must be QEvent::KeyPress, QEvent::KeyRelease, or QEvent::ShortcutOverride.

Int key is the code for the Qt::Key that the event loop should listen for. If key is 0, the event is not a result of a known key; for example, it may be the result of a compose sequence or keyboard macro. The modifiers holds the keyboard modifiers, and the given text is the Unicode text that the key generated. If autorep is true, isAutoRepeat() will be true. count is the number of keys involved in the event.

### int QKeyEvent::count () const

Returns the number of keys involved in this event. If text() is not empty, this is simply the length of the string.

See also Qt::WA_KeyCompression.

### bool QKeyEvent::isAutoRepeat () const

Returns true if this event comes from an auto-repeating key; returns false if it comes from an initial key press.

Note that if the event is a multiple-key compressed event that is partly due to auto-repeat, this function could return either true or false indeterminately.

### int QKeyEvent::key () const

Returns the code of the key that was pressed or released.

See Qt::Key for the list of keyboard codes. These codes are independent of the underlying window system. Note that this function does not distinguish between capital and non-capital letters, use the text() function (returning the Unicode text the key generated) for this purpose.

A value of either 0 or Qt::Key_unknown means that the event is not the result of a known key; for example, it may be the result of a compose sequence, a keyboard macro, or due to key event compression.

See also Qt::WA_KeyCompression.

### bool QKeyEvent::matches ( QKeySequence::StandardKey key ) const

Returns true if the key event matches the given standard key; otherwise returns false.

This function was introduced in Qt 4.2.

### Qt::KeyboardModifiers QKeyEvent::modifiers () const

Returns the keyboard modifier flags that existed immediately after the event occurred.

Warning: This function cannot always be trusted. The user can confuse it by pressing both Shift keys simultaneously and releasing one of them, for example.

See also QApplication::keyboardModifiers().

### quint32 QKeyEvent::nativeModifiers () const

Returns the native modifiers of a key event. If the key event does not contain this data 0 is returned.

Note: The native modifiers may be 0, even if the key event contains extended information.

This function was introduced in Qt 4.2.

### quint32 QKeyEvent::nativeScanCode () const

Returns the native scan code of the key event. If the key event does not contain this data 0 is returned.

Note: The native scan code may be 0, even if the key event contains extended information.

Note: On Mac OS/X, this function is not useful, because there is no way to get the scan code from Carbon or Cocoa. The function always returns 1 (or 0 in the case explained above).

This function was introduced in Qt 4.2.

### quint32 QKeyEvent::nativeVirtualKey () const

Returns the native virtual key, or key sym of the key event. If the key event does not contain this data 0 is returned.

Note: The native virtual key may be 0, even if the key event contains extended information.

This function was introduced in Qt 4.2.

### QString QKeyEvent::text () const

Returns the Unicode text that this key generated. The text returned can be an empty string in cases where modifier keys, such as Shift, Control, Alt, and Meta, are being pressed or released. In such cases key() will contain a valid value.

See also Qt::WA_KeyCompression.

## Related Non-Members

### bool operator== ( QKeySequence::StandardKey key, QKeyEvent * e )

Returns true if key is currently bound to the key combination specified by e.

Equivalent to `e->matches(key)`.

### bool operator== ( QKeyEvent * e, QKeySequence::StandardKey key )

Returns true if key is currently bound to the key combination specified by e.

Equivalent to `e->matches(key)`.