QQmlComponent¶
The
QQmlComponent
class encapsulates a QML component definition. More…
Synopsis¶
Functions¶
def
create
(arg__1[, context=None[, forContext=None]])def
createWithInitialProperties
(initialProperties[, context=None])def
creationContext
()def
engine
()def
errorString
()def
errors
()def
isError
()def
isLoading
()def
isNull
()def
isReady
()def
progress
()def
setInitialProperties
(component, properties)def
status
()def
url
()
Virtual functions¶
def
beginCreate
(arg__1)def
completeCreate
()def
create
([context=None])
Slots¶
Signals¶
def
progressChanged
(arg__1)def
statusChanged
(arg__1)
Detailed Description¶
Components are reusable, encapsulated QML types with well-defined interfaces.
A
QQmlComponent
instance can be created from a QML file. For example, if there is amain.qml
file like this:The following code loads this QML file as a component, creates an instance of this component using
create()
, and then queries the Item ‘s width value:QQmlEngine *engine = new QQmlEngine; QQmlComponent component(engine, QUrl::fromLocalFile("main.qml")); QObject *myObject = component.create(); QQuickItem *item = qobject_cast<QQuickItem*>(myObject); int width = item->width(); // width = 200To create instances of a component in code where a
QQmlEngine
instance is not available, you can useqmlContext()
orqmlEngine()
. For example, in the scenario below, child items are being created within aQQuickItem
subclass:void MyCppItem::init() { QQmlEngine *engine = qmlEngine(this); // Or: // QQmlEngine *engine = qmlContext(this)->engine(); QQmlComponent component(engine, QUrl::fromLocalFile("MyItem.qml")); QQuickItem *childItem = qobject_cast<QQuickItem*>(component.create()); childItem->setParentItem(this); }Note that these functions will return
null
when called inside the constructor of aQObject
subclass, as the instance will not yet have a context nor engine.
Network Components¶
If the URL passed to
QQmlComponent
is a network resource, or if the QML document references a network resource, theQQmlComponent
has to fetch the network data before it is able to create objects. In this case, theQQmlComponent
will have aLoading
status
. An application will have to wait until the component isReady
before callingcreate()
.The following example shows how to load a QML file from a network resource. After creating the
QQmlComponent
, it tests whether the component is loading. If it is, it connects to thestatusChanged()
signal and otherwise calls thecontinueLoading()
method directly. Note thatisLoading()
may be false for a network component if the component has been cached and is ready immediately.MyApplication::MyApplication() { // ... component = new QQmlComponent(engine, QUrl("http://www.example.com/main.qml")); if (component->isLoading()) QObject::connect(component, SIGNAL(statusChanged(QQmlComponent::Status)), this, SLOT(continueLoading())); else continueLoading(); } void MyApplication::continueLoading() { if (component->isError()) { qWarning() << component->errors(); } else { QObject *myObject = component->create(); } }
- class PySide2.QtQml.QQmlComponent([parent=None])¶
PySide2.QtQml.QQmlComponent(arg__1[, parent=None])
PySide2.QtQml.QQmlComponent(arg__1, fileName[, parent=None])
PySide2.QtQml.QQmlComponent(arg__1, fileName, mode[, parent=None])
PySide2.QtQml.QQmlComponent(arg__1, url[, parent=None])
PySide2.QtQml.QQmlComponent(arg__1, url, mode[, parent=None])
- param parent:
- param url:
- param arg__1:
- param fileName:
str
- param mode:
Create a
QQmlComponent
with no data and give it the specifiedengine
andparent
. Set the data withsetData()
.
- PySide2.QtQml.QQmlComponent.CompilationMode¶
Specifies whether the
QQmlComponent
should load the component immediately, or asynchonously.Constant
Description
QQmlComponent.PreferSynchronous
Prefer loading/compiling the component immediately, blocking the thread. This is not always possible; for example, remote URLs will always load asynchronously.
QQmlComponent.Asynchronous
Load/compile the component in a background thread.
- PySide2.QtQml.QQmlComponent.Status¶
Specifies the loading status of the
QQmlComponent
.Constant
Description
QQmlComponent.Null
This
QQmlComponent
has no data. CallloadUrl()
orsetData()
to add QML content.QQmlComponent.Ready
This
QQmlComponent
is ready andcreate()
may be called.QQmlComponent.Loading
This
QQmlComponent
is loading network data.QQmlComponent.Error
An error has occurred. Call
errors()
to retrieve a list oferrors
.
- PySide2.QtQml.QQmlComponent.beginCreate(arg__1)¶
- Parameters:
arg__1 –
PySide2.QtQml.QQmlContext
- Return type:
This method provides advanced control over component instance creation. In general, programmers should use
create()
to create object instances.Create an object instance from this component. Returns
None
if creation failed.publicContext
specifies the context within which to create the object instance.When
QQmlComponent
constructs an instance, it occurs in three steps:The object hierarchy is created, and constant values are assigned.
Property bindings are evaluated for the first time.
If applicable,
componentComplete()
is called on objects.
differs from
create()
in that it only performs step 1.completeCreate()
must be called to complete steps 2 and 3.This breaking point is sometimes useful when using attached properties to communicate information to an instantiated component, as it allows their initial values to be configured before property bindings take effect.
The ownership of the returned object instance is transferred to the caller.
See also
completeCreate()
ObjectOwnership
- PySide2.QtQml.QQmlComponent.completeCreate()¶
This method provides advanced control over component instance creation. In general, programmers should use
create()
to create a component.This function completes the component creation begun with
beginCreate()
and must be called afterwards.See also
- PySide2.QtQml.QQmlComponent.create([context=None])¶
- Parameters:
context –
PySide2.QtQml.QQmlContext
- Return type:
Create an object instance from this component. Returns
None
if creation failed.context
specifies the context within which to create the object instance.If
context
isNone
(the default), it will create the instance in theroot context
of the engine.The ownership of the returned object instance is transferred to the caller.
If the object being created from this component is a visual item, it must have a visual parent, which can be set by calling
setParentItem()
. See Concepts - Visual Parent in Qt Quick for more details.See also
ObjectOwnership
- PySide2.QtQml.QQmlComponent.create(arg__1[, context=None[, forContext=None]])
- Parameters:
arg__1 –
PySide2.QtQml.QQmlIncubator
context –
PySide2.QtQml.QQmlContext
forContext –
PySide2.QtQml.QQmlContext
Create an object instance from this component using the provided
incubator
.context
specifies the context within which to create the object instance.If
context
is 0 (the default), it will create the instance in the engine’sroot context
.forContext
specifies a context that this object creation depends upon. If theforContext
is being created asynchronously, and theIncubationMode
isAsynchronousIfNested
, this object will also be created asynchronously. IfforContext
is 0 (the default), thecontext
will be used for this decision.The created object and its creation status are available via the
incubator
.See also
- PySide2.QtQml.QQmlComponent.createWithInitialProperties(initialProperties[, context=None])¶
- Parameters:
initialProperties –
context –
PySide2.QtQml.QQmlContext
- Return type:
Create an object instance of this component, and initialize its toplevel properties with
initialProperties
.context
specifies the context where the object instance is to be created.If any of the
initialProperties
cannot be set,isError()
will returntrue
, and theerrors()
function can be used to get detailed information about the error(s).See also
- PySide2.QtQml.QQmlComponent.creationContext()¶
- Return type:
Returns the
QQmlContext
the component was created in. This is only valid for components created directly from QML.
- PySide2.QtQml.QQmlComponent.engine()¶
- Return type:
Returns the
QQmlEngine
of this component.
- PySide2.QtQml.QQmlComponent.errorString()¶
- Return type:
str
errorString is only meant as a way to get the errors in script
- PySide2.QtQml.QQmlComponent.errors()¶
- Return type:
Returns the list of errors that occurred during the last compile or create operation. An empty list is returned if
isError()
is not set.
- PySide2.QtQml.QQmlComponent.loadUrl(url)¶
- Parameters:
url –
PySide2.QtCore.QUrl
Load the
QQmlComponent
from the providedurl
.Ensure that the URL provided is full and correct, in particular, use
fromLocalFile()
when loading a file from the local filesystem.Relative paths will be resolved against
baseUrl()
, which is the current working directory unless specified.
- PySide2.QtQml.QQmlComponent.loadUrl(url, mode)
- Parameters:
url –
PySide2.QtCore.QUrl
mode –
CompilationMode
Load the
QQmlComponent
from the providedurl
. Ifmode
isAsynchronous
, the component will be loaded and compiled asynchronously.Ensure that the URL provided is full and correct, in particular, use
fromLocalFile()
when loading a file from the local filesystem.Relative paths will be resolved against
baseUrl()
, which is the current working directory unless specified.
- PySide2.QtQml.QQmlComponent.progress()¶
- Return type:
float
The progress of loading the component, from 0.0 (nothing loaded) to 1.0 (finished).
- PySide2.QtQml.QQmlComponent.progressChanged(arg__1)¶
- Parameters:
arg__1 – float
- PySide2.QtQml.QQmlComponent.setData(arg__1, baseUrl)¶
- Parameters:
arg__1 –
PySide2.QtCore.QByteArray
baseUrl –
PySide2.QtCore.QUrl
Sets the
QQmlComponent
to use the given QMLdata
. Ifurl
is provided, it is used to set the component name and to provide a base path for items resolved by this component.
- PySide2.QtQml.QQmlComponent.setInitialProperties(component, properties)¶
- Parameters:
component –
PySide2.QtCore.QObject
properties –
Set toplevel
properties
of thecomponent
.This method provides advanced control over component instance creation. In general, programmers should use
createWithInitialProperties
to create a component.Use this method after
beginCreate
and beforecompleteCreate
has been called. If a provided property does not exist, a warning is issued.
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