QIcon 类

QIcon 类提供在不同模式和状态下的可缩放图标。 更多...

Header: #include <QIcon>
CMake: find_package(Qt6 COMPONENTS Gui REQUIRED)
target_link_libraries(mytarget PRIVATE Qt6::Gui)
qmake: QT += gui

公共类型

enum 模式 { Normal, Disabled, Active, Selected }
enum State { Off, On }

公共函数

QIcon (QIconEngine * engine )
QIcon (const QString & fileName )
QIcon (QIcon && other )
QIcon (const QIcon & other )
QIcon (const QPixmap & pixmap )
QIcon ()
QIcon & operator= (QIcon && other )
QIcon & operator= (const QIcon & other )
~QIcon ()
QSize actualSize (const QSize & size , QIcon::Mode mode = Normal, QIcon::State state = Off) const
QSize actualSize (QWindow * window , const QSize & size , QIcon::Mode mode = Normal, QIcon::State state = Off) const
void addFile (const QString & fileName , const QSize & size = QSize(), QIcon::Mode mode = Normal, QIcon::State state = Off)
void addPixmap (const QPixmap & pixmap , QIcon::Mode mode = Normal, QIcon::State state = Off)
QList<QSize> availableSizes (QIcon::Mode mode = Normal, QIcon::State state = Off) const
qint64 cacheKey () const
bool isMask () const
bool isNull () const
QString name () const
void paint (QPainter * painter , const QRect & rect , Qt::Alignment alignment = Qt::AlignCenter, QIcon::Mode mode = Normal, QIcon::State state = Off) const
void paint (QPainter * painter , int x , int y , int w , int h , Qt::Alignment alignment = Qt::AlignCenter, QIcon::Mode mode = Normal, QIcon::State state = Off) const
QPixmap pixmap (const QSize & size , QIcon::Mode mode = Normal, QIcon::State state = Off) const
QPixmap pixmap (int w , int h , QIcon::Mode mode = Normal, QIcon::State state = Off) const
QPixmap pixmap (int extent , QIcon::Mode mode = Normal, QIcon::State state = Off) const
QPixmap pixmap (const QSize & size , qreal devicePixelRatio , QIcon::Mode mode = Normal, QIcon::State state = Off) const
void setIsMask (bool isMask )
void swap (QIcon & other )
QVariant operator QVariant () const

静态公共成员

QStringList fallbackSearchPaths ()
QString fallbackThemeName ()
QIcon fromTheme (const QString & name )
QIcon fromTheme (const QString & name , const QIcon & fallback )
bool hasThemeIcon (const QString & name )
void setFallbackSearchPaths (const QStringList & paths )
void setFallbackThemeName (const QString & name )
void setThemeName (const QString & name )
void setThemeSearchPaths (const QStringList & paths )
QString themeName ()
QStringList themeSearchPaths ()
QDataStream & operator<< (QDataStream & stream , const QIcon & icon )
QDataStream & operator>> (QDataStream & stream , QIcon & icon )

详细描述

A QIcon can generate smaller, larger, active, and disabled pixmaps from the set of pixmaps it is given. Such pixmaps are used by Qt widgets to show an icon representing a particular action.

The simplest use of QIcon is to create one from a QPixmap file or resource, and then use it, allowing Qt to work out all the required icon styles and sizes. For example:

QToolButton *button = new QToolButton;
button->setIcon(QIcon("open.xpm"));
							

To undo a QIcon, simply set a null icon in its place:

button->setIcon(QIcon());
							

使用 QImageReader::supportedImageFormats () 和 QImageWriter::supportedImageFormats () functions to retrieve a complete list of the supported file formats.

When you retrieve a pixmap using pixmap( QSize , Mode, State), and no pixmap for this given size, mode and state has been added with addFile () 或 addPixmap (), then QIcon will generate one on the fly. This pixmap generation happens in a QIconEngine . The default engine scales pixmaps down if required, but never up, and it uses the current style to calculate a disabled appearance. By using custom icon engines, you can customize every aspect of generated icons. With QIconEnginePlugin it is possible to register different icon engines for different file suffixes, making it possible for third parties to provide additional icon engines to those included with Qt.

注意: Since Qt 4.2, an icon engine that supports SVG is included.

Making Classes that Use QIcon

If you write your own widgets that have an option to set a small pixmap, consider allowing a QIcon to be set for that pixmap. The Qt class QToolButton is an example of such a widget.

Provide a method to set a QIcon, and when you draw the icon, choose whichever pixmap is appropriate for the current state of your widget. For example:

void MyWidget::drawIcon(QPainter *painter, QPoint pos)
{
    QPixmap pixmap = icon.pixmap(QSize(22, 22),
                                   isEnabled() ? QIcon::Normal
                                               : QIcon::Disabled,
                                   isChecked() ? QIcon::On
                                               : QIcon::Off);
    painter->drawPixmap(pos, pixmap);
}
							

You might also make use of the Active mode, perhaps making your widget Active when the mouse is over the widget (see QWidget::enterEvent ()), while the mouse is pressed pending the release that will activate the function, or when it is the currently selected item. If the widget can be toggled, the "On" mode might be used to draw a different icon.

QIcon

注意: QIcon needs a QGuiApplication instance before the icon is created.

High DPI Icons

There are two ways that QIcon supports high DPI icons: via addFile () 和 fromTheme ().

addFile () is useful if you have your own custom directory structure and do not need to use the freedesktop.org Icon Theme Specification . Icons created via this approach use Qt's "@nx" high DPI syntax .

使用 fromTheme () is necessary if you plan on following the Icon Theme Specification. To make QIcon use the high DPI version of an image, add an additional entry to the appropriate index.theme 文件:

[Icon Theme]
Name=Test
Comment=Test Theme
Directories=32x32/actions,32x32@2/actions
[32x32/actions]
Size=32
Context=Actions
Type=Fixed
# High DPI version of the entry above.
[32x32@2/actions]
Size=32
Scale=2
Type=Fixed
							

Your icon theme directory would then look something like this:

├── 32x32
│   └── actions
│       └── appointment-new.png
├── 32x32@2
│   └── actions
│       └── appointment-new.png
└── index.theme
							

另请参阅 GUI Design Handbook: Iconic Label and 图标范例 .

成员类型文档编制

enum QIcon:: 模式

This enum type describes the mode for which a pixmap is intended to be used. The currently defined modes are:

常量 描述
QIcon::Normal 0 Display the pixmap when the user is not interacting with the icon, but the functionality represented by the icon is available.
QIcon::Disabled 1 Display the pixmap when the functionality represented by the icon is not available.
QIcon::Active 2 Display the pixmap when the functionality represented by the icon is available and the user is interacting with the icon, for example, moving the mouse over it or clicking it.
QIcon::Selected 3 Display the pixmap when the item represented by the icon is selected.

enum QIcon:: State

This enum describes the state for which a pixmap is intended to be used. The state can be:

常量 描述
QIcon::Off 1 Display the pixmap when the widget is in an "off" state
QIcon::On 0 Display the pixmap when the widget is in an "on" state

成员函数文档编制

QIcon:: QIcon ( QIconEngine * engine )

Creates an icon with a specific icon engine . The icon takes ownership of the engine.

QIcon:: QIcon (const QString & fileName )

Constructs an icon from the file with the given fileName . The file will be loaded on demand.

fileName contains a relative path (e.g. the filename only) the relevant file must be found relative to the runtime working directory.

The file name can refer to an actual file on disk or to one of the application's embedded resources. See the 资源系统 概述,了解如何在应用程序可执行文件中嵌入图像及其它资源文件的细节。

使用 QImageReader::supportedImageFormats () 和 QImageWriter::supportedImageFormats () functions to retrieve a complete list of the supported file formats.

QIcon:: QIcon ( QIcon && other )

Move-constructs a QIcon instance, making it point to the same object that other 所指向的。

QIcon:: QIcon (const QIcon & other )

构造副本为 other . This is very fast.

QIcon:: QIcon (const QPixmap & pixmap )

Constructs an icon from a pixmap .

QIcon:: QIcon ()

Constructs a null icon.

[since 5.2] QIcon &QIcon:: operator= ( QIcon && other )

移动赋值 other 到此 QIcon 实例。

该函数在 Qt 5.2 引入。

QIcon &QIcon:: operator= (const QIcon & other )

赋值 other icon to this icon and returns a reference to this icon.

QIcon:: ~QIcon ()

Destroys the icon.

QSize QIcon:: actualSize (const QSize & size , QIcon::Mode mode = Normal, QIcon::State state = Off) const

Returns the actual size of the icon for the requested size , mode ,和 state . The result might be smaller than requested, but never larger. The returned size is in device-independent pixels (This is relevant for high-dpi pixmaps.)

另请参阅 pixmap () 和 paint ().

[since 5.1] QSize QIcon:: actualSize ( QWindow * window , const QSize & size , QIcon::Mode mode = Normal, QIcon::State state = Off) const

Returns the actual size of the icon for the requested window size , mode ,和 state .

The pixmap can be smaller than the requested size. The returned size is in device-independent pixels (This is relevant for high-dpi pixmaps.)

该函数在 Qt 5.1 引入。

另请参阅 actualSize (), pixmap (),和 paint ().

void QIcon:: addFile (const QString & fileName , const QSize & size = QSize(), QIcon::Mode mode = Normal, QIcon::State state = Off)

Adds an image from the file with the given fileName to the icon, as a specialization for size , mode and state . The file will be loaded on demand. Note: custom icon engines are free to ignore additionally added pixmaps.

fileName contains a relative path (e.g. the filename only) the relevant file must be found relative to the runtime working directory.

The file name can refer to an actual file on disk or to one of the application's embedded resources. See the 资源系统 概述,了解如何在应用程序可执行文件中嵌入图像及其它资源文件的细节。

使用 QImageReader::supportedImageFormats () 和 QImageWriter::supportedImageFormats () functions to retrieve a complete list of the supported file formats.

If a high resolution version of the image exists (identified by the suffix @2x on the base name), it is automatically loaded and added with the 设备像素比率 set to a value of 2. This can be disabled by setting the environment variable QT_HIGHDPI_DISABLE_2X_IMAGE_LOADING (见 QImageReader ).

注意: When you add a non-empty filename to a QIcon , the icon becomes non-null, even if the file doesn't exist or points to a corrupt file.

另请参阅 addPixmap () 和 QPixmap::devicePixelRatio ().

void QIcon:: addPixmap (const QPixmap & pixmap , QIcon::Mode mode = Normal, QIcon::State state = Off)

添加 pixmap to the icon, as a specialization for mode and state .

Custom icon engines are free to ignore additionally added pixmaps.

另请参阅 addFile ().

QList < QSize > QIcon:: availableSizes ( QIcon::Mode mode = Normal, QIcon::State state = Off) const

Returns a list of available icon sizes for the specified mode and state .

qint64 QIcon:: cacheKey () const

Returns a number that identifies the contents of this QIcon object. Distinct QIcon objects can have the same key if they refer to the same contents.

The cacheKey() will change when the icon is altered via addPixmap () 或 addFile ().

Cache keys are mostly useful in conjunction with caching.

另请参阅 QPixmap::cacheKey ().

[static, since 5.11] QStringList QIcon:: fallbackSearchPaths ()

Returns the fallback search paths for icons.

The default value will depend on the platform.

该函数在 Qt 5.11 引入。

另请参阅 setFallbackSearchPaths () 和 themeSearchPaths ().

[static, since 5.12] QString QIcon:: fallbackThemeName ()

Returns the name of the fallback icon theme.

On X11, if not set, the fallback icon theme depends on your desktop settings. On other platforms it is not set by default.

该函数在 Qt 5.12 引入。

另请参阅 setFallbackThemeName () 和 themeName ().

[static] QIcon QIcon:: fromTheme (const QString & name )

返回 QIcon corresponding to name in the current icon theme.

The latest version of the freedesktop icon specification and naming specification can be obtained here:

To fetch an icon from the current icon theme:

QIcon undoicon = QIcon::fromTheme("edit-undo");
							

注意: By default, only X11 will support themed icons. In order to use themed icons on Mac and Windows, you will have to bundle a compliant theme in one of your themeSearchPaths () and set the appropriate themeName ().

注意: Qt will make use of GTK's icon-theme.cache if present to speed up the lookup. These caches can be generated using gtk-update-icon-cache: https://developer.gnome.org/gtk3/stable/gtk-update-icon-cache.html .

注意: If an icon can't be found in the current theme, then it will be searched in fallbackSearchPaths () as an unthemed icon.

另请参阅 themeName (), setThemeName (), themeSearchPaths (),和 fallbackSearchPaths ().

[static] QIcon QIcon:: fromTheme (const QString & name , const QIcon & fallback )

这是重载函数。

返回 QIcon corresponding to name in the current icon theme. If no such icon is found in the current theme fallback 被返回取而代之。

If you want to provide a guaranteed fallback for platforms that do not support theme icons, you can use the second argument:

QIcon undoicon = QIcon::fromTheme("edit-undo", QIcon(":/undo.png"));
							

[static] bool QIcon:: hasThemeIcon (const QString & name )

返回 true if there is an icon available for name in the current icon theme, otherwise returns false .

另请参阅 themeSearchPaths (), fromTheme (),和 setThemeName ().

[since 5.6] bool QIcon:: isMask () const

返回 true if this icon has been marked as a mask image. Certain platforms render mask icons differently (for example, menu icons on macOS).

该函数在 Qt 5.6 引入。

另请参阅 setIsMask ().

bool QIcon:: isNull () const

返回 true if the icon is empty; otherwise returns false .

An icon is empty if it has neither a pixmap nor a filename.

Note: Even a non-null icon might not be able to create valid pixmaps, eg. if the file does not exist or cannot be read.

QString QIcon:: name () const

Returns the name used to create the icon, if available.

Depending on the way the icon was created, it may have an associated name. This is the case for icons created with fromTheme () or icons using a QIconEngine which supports the QIconEngine::IconNameHook.

另请参阅 fromTheme () 和 QIconEngine .

void QIcon:: paint ( QPainter * painter , const QRect & rect , Qt::Alignment alignment = Qt::AlignCenter, QIcon::Mode mode = Normal, QIcon::State state = Off) const

Uses the painter to paint the icon with specified alignment , required mode ,和 state into the rectangle rect .

另请参阅 actualSize () 和 pixmap ().

void QIcon:: paint ( QPainter * painter , int x , int y , int w , int h , Qt::Alignment alignment = Qt::AlignCenter, QIcon::Mode mode = Normal, QIcon::State state = Off) const

这是重载函数。

Paints the icon into the rectangle QRect ( x , y , w , h ).

QPixmap QIcon:: pixmap (const QSize & size , QIcon::Mode mode = Normal, QIcon::State state = Off) const

Returns a pixmap with the requested size , mode ,和 state , generating one if necessary. The pixmap might be smaller than requested, but never larger, unless the device-pixel ratio of the returned pixmap is larger than 1.

另请参阅 actualSize () 和 paint ().

QPixmap QIcon:: pixmap ( int w , int h , QIcon::Mode mode = Normal, QIcon::State state = Off) const

这是重载函数。

Returns a pixmap of size QSize ( w , h ). The pixmap might be smaller than requested, but never larger, unless the device-pixel ratio of the returned pixmap is larger than 1.

QPixmap QIcon:: pixmap ( int extent , QIcon::Mode mode = Normal, QIcon::State state = Off) const

这是重载函数。

Returns a pixmap of size QSize ( extent , extent ). The pixmap might be smaller than requested, but never larger, unless the device-pixel ratio of the returned pixmap is larger than 1.

[since 6.0] QPixmap QIcon:: pixmap (const QSize & size , qreal devicePixelRatio , QIcon::Mode mode = Normal, QIcon::State state = Off) const

这是重载函数。

Returns a pixmap with the requested size , devicePixelRatio , mode ,和 state , generating one if necessary.

该函数在 Qt 6.0 引入。

另请参阅 actualSize () 和 paint ().

[static, since 5.11] void QIcon:: setFallbackSearchPaths (const QStringList & paths )

Sets the fallback search paths for icons to paths .

注意: To add some path without replacing existing ones:

QIcon::setFallbackSearchPaths(QIcon::fallbackSearchPaths() << "my/search/path");
							

该函数在 Qt 5.11 引入。

另请参阅 fallbackSearchPaths () 和 setThemeSearchPaths ().

[static, since 5.12] void QIcon:: setFallbackThemeName (const QString & name )

Sets the fallback icon theme to name .

name should correspond to a directory name in the themeSearchPath() containing an index.theme file describing its contents.

注意: This should be done before creating QGuiApplication , to ensure correct initialization.

该函数在 Qt 5.12 引入。

另请参阅 fallbackThemeName (), themeSearchPaths (),和 themeName ().

[since 5.6] void QIcon:: setIsMask ( bool isMask )

Indicate that this icon is a mask image(boolean isMask ), and hence can potentially be modified based on where it's displayed.

该函数在 Qt 5.6 引入。

另请参阅 isMask ().

[static] void QIcon:: setThemeName (const QString & name )

Sets the current icon theme to name .

name should correspond to a directory name in the themeSearchPath() containing an index.theme file describing its contents.

另请参阅 themeSearchPaths () 和 themeName ().

[static] void QIcon:: setThemeSearchPaths (const QStringList & paths )

Sets the search paths for icon themes to paths .

另请参阅 themeSearchPaths (), fromTheme (),和 setThemeName ().

void QIcon:: swap ( QIcon & other )

Swaps icon other with this icon. This operation is very fast and never fails.

[static] QString QIcon:: themeName ()

Returns the name of the current icon theme.

On X11, the current icon theme depends on your desktop settings. On other platforms it is not set by default.

另请参阅 setThemeName (), themeSearchPaths (), fromTheme (),和 hasThemeIcon ().

[static] QStringList QIcon:: themeSearchPaths ()

Returns the search paths for icon themes.

The default value will depend on the platform:

On X11, the search path will use the XDG_DATA_DIRS environment variable if available.

By default all platforms will have the resource directory :\icons as a fallback. You can use "rcc -project" to generate a resource file from your icon theme.

另请参阅 setThemeSearchPaths (), fromTheme (),和 setThemeName ().

QVariant QIcon:: operator QVariant () const

Returns the icon as a QVariant .

相关非成员

QDataStream & operator<< ( QDataStream & stream , const QIcon & icon )

写入给定 icon 到给定 stream as a PNG image. If the icon contains more than one image, all images will be written to the stream. Note that writing the stream to a file will not produce a valid image file.

QDataStream & operator>> ( QDataStream & stream , QIcon & icon )

Reads an image, or a set of images, from the given stream 进给定 icon .