The QDeclarativeProperty class abstracts accessing properties on objects created from QML. 更多...
The QDeclarativeProperty class abstracts accessing properties on objects created from QML.
As QML uses Qt's meta-type system all of the existing QMetaObject classes can be used to introspect and interact with objects created by QML. However, some of the new features provided by QML - such as type safety and attached properties - are most easily used through the QDeclarativeProperty class that simplifies some of their natural complexity.
不像 QMetaProperty which represents a property on a class type, QDeclarativeProperty encapsulates a property on a specific object instance. To read a property's value, programmers create a QDeclarativeProperty instance and call the read () method. Likewise to write a property value the write () method is used.
For example, for the following QML code:
// MyItem.qml import QtQuick 1.0 Text { text: "A bit of text" }
文本 object's properties could be accessed using QDeclarativeProperty, like this:
#include <QDeclarativeProperty> #include <QGraphicsObject> ... QDeclarativeView view(QUrl.fromLocalFile("MyItem.qml")); QDeclarativeProperty property(view.rootObject(), "font.pixelSize"); qWarning() << "Current pixel size:" << property.read().toInt(); property.write(24); qWarning() << "Pixel size should now be 24:" << property.read().toInt();
This enum specifies a category of QML property.
| 常量 | 值 | 描述 |
|---|---|---|
| QDeclarativeProperty.InvalidCategory | 0 | The property is invalid, or is a signal 特性。 |
| QDeclarativeProperty.List | 1 | The property is a QDeclarativeListProperty list property |
| QDeclarativeProperty.Object | 2 | The property is a QObject derived type pointer |
| QDeclarativeProperty.Normal | 3 | The property is a normal value property. |
This enum specifies a type of QML property.
| 常量 | 值 | 描述 |
|---|---|---|
| QDeclarativeProperty.Invalid | 0 | The property is invalid. |
| QDeclarativeProperty.Property | 1 | The property is a regular Qt property. |
| QDeclarativeProperty.SignalProperty | 2 | The property is a signal property. |
Create an invalid QDeclarativeProperty .
创建 QDeclarativeProperty 为 default property of obj . If there is no default property, an invalid QDeclarativeProperty 将是 created.
创建 QDeclarativeProperty 为 default property of obj 使用 context ctxt . If there is no default property, an invalid QDeclarativeProperty 将是 created.
创建 QDeclarativeProperty 为 default property of obj using the environment for instantiating QML components that is provided by engine 。若 there is no default property, an invalid QDeclarativeProperty 将是 created.
创建 QDeclarativeProperty 为 property name of obj .
创建 QDeclarativeProperty 为 property name of obj 使用 context ctxt .
Creating a QDeclarativeProperty without a context will render some properties - like attached properties - inaccessible.
创建 QDeclarativeProperty 为 property name of obj using the environment for instantiating QML components that is provided by engine .
Create a copy of other .
Connects the property's change notifier signal to the specified slot 的 dest object and returns true. Returns false if this metaproperty does not represent a regular Qt property or if it has no change notifier signal, or if the dest object does not have the specified slot .
Connects the property's change notifier signal to the specified 方法 的 dest object and returns true. Returns false if this metaproperty does not represent a regular Qt property or if it has no change notifier signal, or if the dest object does not have the specified 方法 .
Returns true if the property has a change notifier signal, otherwise false.
Return the Qt metaobject index of the property.
Returns true if the property is designable, otherwise false.
返回 true，若此 QDeclarativeProperty represents a regular Qt property.
Returns true if the property is resettable, otherwise false.
返回 true，若此 QDeclarativeProperty represents a QML signal property.
返回 true 若 QDeclarativeProperty refers to a valid property, otherwise false.
Returns true if the property is writable, otherwise false.
返回 QMetaMethod for this property if it is a SignalProperty , otherwise returns an invalid QMetaMethod .
Return the name of this QML property.
Returns true if the property needs a change notifier signal for bindings to remain upto date, false otherwise.
Some properties, such as attached properties or those whose value never changes, do not require a change notifier.
返回 QDeclarativeProperty 's QObject .
返回 Qt property associated with this QML property.
返回 QVariant type of the property, or QVariant.Invalid if the property has no QVariant 类型。
Returns the property category.
Returns the type name of the property, or 0 if the property has no type name.
Returns the property value.
返回 name property value of object . This method is equivalent to:
QDeclarativeProperty p(object, name); p.read();
返回 name property value of object 使用 context ctxt . This method is equivalent to:
QDeclarativeProperty p(object, name, context); p.read();
返回 name property value of object 使用 environment for instantiating QML components that is provided by engine . . This method is equivalent to:
QDeclarativeProperty p(object, name, engine); p.read();
Resets the property and returns true if the property is resettable. If the property is not resettable, nothing happens and false is returned.
Returns the type of the property.
Sets the property value to value and returns true. Returns false if the property can't be set because the value is the wrong type, for example.
写入 value 到 name property of object . This method is equivalent to:
QDeclarativeProperty p(object, name); p.write(value);
写入 value 到 name property of object 使用 context ctxt . This method is equivalent to:
QDeclarativeProperty p(object, name, ctxt); p.write(value);
写入 value 到 name property of object using the environment for instantiating QML components that is provided by engine . This method is equivalent to:
QDeclarativeProperty p(object, name, engine); p.write(value);
