QUiLoader

The QUiLoader class enables standalone applications to dynamically create user interfaces at run-time using the information stored in UI files or specified in plugin paths. More

Inheritance diagram of PySide2.QtUiTools.QUiLoader

Synopsis

Functions

Virtual functions

Detailed Description

In addition, you can customize or create your own user interface by deriving your own loader class.

If you have a custom component or an application that embeds Qt Designer , you can also use the QFormBuilder class provided by the QtDesigner module to create user interfaces from UI files.

The QUiLoader class provides a collection of functions allowing you to create widgets based on the information stored in UI files (created with Qt Designer ) or available in the specified plugin paths. The specified plugin paths can be retrieved using the pluginPaths() function. Similarly, the contents of a UI file can be retrieved using the load() function. For example:

MyWidget::MyWidget(QWidget *parent)
    : QWidget(parent)
{
    QUiLoader loader;
    QFile file(":/forms/myform.ui");
    file.open(QFile::ReadOnly);
    QWidget *myWidget = loader.load(&file, this);
    file.close();

    QVBoxLayout *layout = new QVBoxLayout;
    layout->addWidget(myWidget);
    setLayout(layout);
}

The availableWidgets() function returns a QStringList with the class names of the widgets available in the specified plugin paths. To create these widgets, simply use the createWidget() function. For example:

QWidget *loadCustomWidget(QWidget *parent)
{
    QUiLoader loader;
    QWidget *myWidget;

    QStringList availableWidgets = loader.availableWidgets();

    if (availableWidgets.contains("AnalogClock"))
        myWidget = loader.createWidget("AnalogClock", parent);

    return myWidget;
}

To make a custom widget available to the loader, you can use the addPluginPath() function; to remove all available widgets, you can call the clearPluginPaths() function.

The createAction() , createActionGroup() , createLayout() , and createWidget() functions are used internally by the QUiLoader class whenever it has to create an action, action group, layout, or widget respectively. For that reason, you can subclass the QUiLoader class and reimplement these functions to intervene the process of constructing a user interface. For example, you might want to have a list of the actions created when loading a form or creating a custom widget.

For a complete example using the QUiLoader class, see the Calculator Builder Example.

See also

Qt UI Tools QFormBuilder

class QUiLoader([parent=None])
param parent

QObject

Creates a form loader with the given parent .

PySide2.QtUiTools.QUiLoader.addPluginPath(path)
Parameters

path – unicode

Adds the given path to the list of paths in which the loader will search when locating plugins.

PySide2.QtUiTools.QUiLoader.availableLayouts()
Return type

list of strings

Returns a list naming all available layouts that can be built using the createLayout() function

See also

createLayout()

PySide2.QtUiTools.QUiLoader.availableWidgets()
Return type

list of strings

Returns a list naming all available widgets that can be built using the createWidget() function, i.e all the widgets specified within the given plugin paths.

PySide2.QtUiTools.QUiLoader.clearPluginPaths()

Clears the list of paths in which the loader will search when locating plugins.

PySide2.QtUiTools.QUiLoader.createAction([parent=None[, name=""]])
Parameters
  • parentQObject

  • name – unicode

Return type

QAction

Creates a new action with the given parent and name .

The function is also used internally by the QUiLoader class whenever it creates a widget. Hence, you can subclass QUiLoader and reimplement this function to intervene process of constructing a user interface or widget. However, in your implementation, ensure that you call QUiLoader ‘s version first.

PySide2.QtUiTools.QUiLoader.createActionGroup([parent=None[, name=""]])
Parameters
  • parentQObject

  • name – unicode

Return type

QActionGroup

Creates a new action group with the given parent and name .

The function is also used internally by the QUiLoader class whenever it creates a widget. Hence, you can subclass QUiLoader and reimplement this function to intervene process of constructing a user interface or widget. However, in your implementation, ensure that you call QUiLoader ‘s version first.

PySide2.QtUiTools.QUiLoader.createLayout(className[, parent=None[, name=""]])
Parameters
  • className – unicode

  • parentQObject

  • name – unicode

Return type

QLayout

Creates a new layout with the given parent and name using the class specified by className .

The function is also used internally by the QUiLoader class whenever it creates a widget. Hence, you can subclass QUiLoader and reimplement this function to intervene process of constructing a user interface or widget. However, in your implementation, ensure that you call QUiLoader ‘s version first.

PySide2.QtUiTools.QUiLoader.createWidget(className[, parent=None[, name=""]])
Parameters
  • className – unicode

  • parentQWidget

  • name – unicode

Return type

QWidget

Creates a new widget with the given parent and name using the class specified by className . You can use this function to create any of the widgets returned by the availableWidgets() function.

The function is also used internally by the QUiLoader class whenever it creates a widget. Hence, you can subclass QUiLoader and reimplement this function to intervene process of constructing a user interface or widget. However, in your implementation, ensure that you call QUiLoader ‘s version first.

PySide2.QtUiTools.QUiLoader.errorString()
Return type

unicode

Returns a human-readable description of the last error occurred in load() .

See also

load()

PySide2.QtUiTools.QUiLoader.isLanguageChangeEnabled()
Return type

bool

Returns true if dynamic retranslation on language change is enabled; returns false otherwise.

PySide2.QtUiTools.QUiLoader.isTranslationEnabled()
Return type

bool

Returns true if translation is enabled; returns false otherwise.

PySide2.QtUiTools.QUiLoader.load(device[, parentWidget=None])
Parameters
  • deviceQIODevice

  • parentWidgetQWidget

Return type

QWidget

Loads a form from the given device and creates a new widget with the given parentWidget to hold its contents.

PySide2.QtUiTools.QUiLoader.load(arg__1[, parentWidget=None])
Parameters
  • arg__1 – unicode

  • parentWidgetQWidget

Return type

QWidget

PySide2.QtUiTools.QUiLoader.pluginPaths()
Return type

list of strings

Returns a list naming the paths in which the loader will search when locating custom widget plugins.

PySide2.QtUiTools.QUiLoader.registerCustomWidget(customWidgetType)
Parameters

customWidgetTypePyObject

Registers a Python created custom widget to QUiLoader, so it can be recognized when

loading a .ui file. The custom widget type is passed via the customWidgetType argument. This is needed when you want to override a virtual method of some widget in the interface, since duck punching will not work with widgets created by QUiLoader based on the contents of the .ui file.

(Remember that duck punching virtual methods is an invitation for your own demise!)

Let’s see an obvious example. If you want to create a new widget it’s probable you’ll end up overriding QWidget’s paintEvent() method.

class Circle(QWidget):
    def paintEvent(self, event):
        painter = QPainter(self)
        painter.setPen(self.pen)
        painter.setBrush(QBrush(self.color))
        painter.drawEllipse(event.rect().center(), 20, 20)

# ...

loader = QUiLoader()
loader.registerCustomWidget(Circle)
circle = loader.load('circle.ui')
circle.show()

# ...
PySide2.QtUiTools.QUiLoader.setLanguageChangeEnabled(enabled)
Parameters

enabledbool

If enabled is true, user interfaces loaded by this loader will automatically retranslate themselves upon receiving a language change event. Otherwise, the user interfaces will not be retranslated.

PySide2.QtUiTools.QUiLoader.setTranslationEnabled(enabled)
Parameters

enabledbool

If enabled is true, user interfaces loaded by this loader will be translated. Otherwise, the user interfaces will not be translated.

Note

This is orthogonal to languageChangeEnabled.

PySide2.QtUiTools.QUiLoader.setWorkingDirectory(dir)
Parameters

dirQDir

Sets the working directory of the loader to dir . The loader will look for other resources, such as icons and resource files, in paths relative to this directory.

PySide2.QtUiTools.QUiLoader.workingDirectory()
Return type

QDir

Returns the working directory of the loader.