内容

• 公共类型
• 公共函数
• 静态公共成员
• 相关非成员
• 详细描述
• 制作使用 QIcon 的类
• 高 DPI 图标

QIcon 类

QIcon 类提供在不同模式和状态下的可伸缩图标。 更多...

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

• 所有成员列表，包括继承成员
• 弃用成员

公共类型

enum	Mode { 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
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 ()

相关非成员

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

详细描述

QIcon 可以从给定像素图集，生成更小、更大、活动及禁用的像素图。Qt 小部件使用这种像素图来展示表示特定动作的图标。

QIcon 的最简单用法是创建一个从 QPixmap 文件 (或资源)，然后使用它，允许 Qt 算出所有要求图标的样式和大小。例如：

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

要撤消 QIcon，只需将其设为 null 图标：

button->setIcon(QIcon());
					

使用 QImageReader::supportedImageFormats () 和 QImageWriter::supportedImageFormats () 函数能检索支持文件格式的完整列表。

当检索像素图使用 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.

制作使用 QIcon 的类

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.

注意： QIcon 需要 QGuiApplication 实例在创建图标之前。

高 DPI 图标

There are two ways that QIcon supports 高 DPI (每英寸点数) 图标：凭借 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 设计手册：图标化标签 and 图标范例 .

成员类型文档编制

enum QIcon:: Mode

此枚举类型描述旨在使用的像素图模式。目前定义的模式：

常量	值	描述
QIcon::Normal	0	显示像素图当用户未与图标交互时，但由图标表示的功能是可用的。
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	显示像素图当由图标表示的项被选中时。

enum QIcon:: State

此枚举描述旨在使用的像素图状态。 state 可以是：

常量	值	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 )

创建图标采用特定图标 engine 。图标拥有引擎的所有权。

QIcon:: QIcon (const QString & fileName )

构造图标从文件采用给定 fileName 。将按需加载文件。

若 fileName 包含相对路径 (如：仅文件名)，必须相对运行时工作目录查找相关文件。

文件名可以引用实际磁盘文件或应用程序嵌入资源之一。见 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 () 函数能检索支持文件格式的完整列表。

QIcon:: QIcon ( QIcon && other )

移动构造 QIcon 实例，使它指向同一对象 other 所指向的。

QIcon:: QIcon (const QIcon & other )

构造副本为 other 。这非常快。

QIcon:: QIcon (const QPixmap & pixmap )

构造图标从 pixmap .

QIcon:: QIcon ()

构造 null 图标。

[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 图标到此图标并返回此图标的引用。

QIcon:: ~QIcon ()

销毁图标。

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 ().

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 到图标，作为特殊化为 size , mode and state . The file will be loaded on demand. Note: custom icon engines are free to ignore additionally added pixmaps.

若 fileName 包含相对路径 (如：仅文件名)，必须相对运行时工作目录查找相关文件。

文件名可以引用实际磁盘文件或应用程序嵌入资源之一。见 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 () 函数能检索支持文件格式的完整列表。

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 到图标，作为特殊化为 mode and state .

自定义图标引擎可自由忽略额外添加的像素图。

另请参阅 addFile ().

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

返回可用图标大小的列表为指定 mode and state .

qint64 QIcon:: cacheKey () const

返回的数字标识内容对于此 QIcon 对象。截然不同的 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 ()

返回用于图标的回退搜索路径。

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 ()

返回回退图标主题的名称。

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 对应 name 在当前图标主题。

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

• http://standards.freedesktop.org/icon-theme-spec/icon-theme-spec-latest.html
• http://standards.freedesktop.org/icon-naming-spec/icon-naming-spec-latest.html

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 对应 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 若图标为空；否则返回 false .

图标为空，若既没有像素图也没有文件名。

注意：即使非 null 图标也可能无法创建有效像素图 (如若文件不存在，或无法读取)。

QString QIcon:: name () const

返回用于创建图标的名称，若可用。

从属图标的创建方式，它可能有关联名称。这是用于创建图标的情况采用 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

使用 painter 来描绘图标采用指定 alignment ，要求 mode ，和 state 到矩形 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。

将图标描绘到矩形 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 )

将回退图标主题设为 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 )

将当前图标主题设为 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 )

交换图标 other 与此图标。此操作非常快且从不失败。

[static] QString QIcon:: themeName ()

返回当前图标主题的名称。

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 ()

返回图标主题的搜索路径。

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 )

读取图像 (或一组图像) 从给定 stream 进给定 icon .