QQmlPropertyMap ¶

概要 ¶

详细描述 ¶

QQmlPropertyMap provides a convenient way to expose domain data to the UI layer. The following example shows how you might declare data in C++ and then access it in QML.

In the C++ file:

// create our data
QQmlPropertyMap ownerData;
ownerData.insert("name", QVariant(QString("John Smith")));
ownerData.insert("phone", QVariant(QString("555-5555")));
// expose it to the UI layer
QQuickView view;
QQmlContext *ctxt = view.rootContext();
ctxt->setContextProperty("owner", &ownerData);
view.setSource(QUrl::fromLocalFile("main.qml"));
view.show();
											

Then, in main.qml :

Text { text: owner.name + " " + owner.phone }
											

The binding is dynamic - whenever a key’s value is updated, anything bound to that key will be updated as well.

To detect value changes made in the UI layer you can connect to the valueChanged() signal. However, note that valueChanged() is NOT emitted when changes are made by calling insert() or clear() - it is only emitted when a value is updated from QML.

注意

It is not possible to remove keys from the map; once a key has been added, you can only modify or clear its associated value.

注意

When deriving a class from QQmlPropertyMap , use the protected two-argument 构造函数 which ensures that the class is correctly registered with the Qt 元对象系统 .

注意

QMetaObject of a QQmlPropertyMap is dynamically generated and modified. Operations on that meta object are not thread safe, so applications need to take care to explicitly synchronize access to the meta object.

class QQmlPropertyMap ( [ parent=None ] ) ¶

param parent

QObject

Constructs a bindable map with parent object parent .

PySide2.QtQml.QQmlPropertyMap. clear ( key ) ¶

参数

key – unicode

Clears the value (if any) associated with key .

PySide2.QtQml.QQmlPropertyMap. contains ( key ) ¶

参数

key – unicode

返回类型

bool

Returns true if the map contains key .

另请参阅

size()

PySide2.QtQml.QQmlPropertyMap. count ( ) ¶

返回类型

int

这是重载函数。

如同 size() .

PySide2.QtQml.QQmlPropertyMap. insert ( key , value ) ¶

参数

• key – unicode

• value – object

Sets the value associated with key to value .

If the key doesn’t exist, it is automatically created.

PySide2.QtQml.QQmlPropertyMap. isEmpty ( ) ¶

返回类型

bool

Returns true if the map contains no keys; otherwise returns false.

另请参阅

size()

PySide2.QtQml.QQmlPropertyMap. keys ( ) ¶

返回类型

字符串列表

Returns the list of keys.

Keys that have been cleared will still appear in this list, even though their associated values are invalid QVariants.

PySide2.QtQml.QQmlPropertyMap.operator[](key)

参数

key – unicode

返回类型

object

这是重载函数。

如同 value() .

PySide2.QtQml.QQmlPropertyMap. size ( ) ¶

返回类型

int

Returns the number of keys in the map.

另请参阅

isEmpty() count()

PySide2.QtQml.QQmlPropertyMap. updateValue ( key , input ) ¶

参数

• key – unicode

• input – object

返回类型

object

Returns the new value to be stored for the key key . This function is provided to intercept updates to a property from QML, where the value provided from QML is input .

Override this function to manipulate the property value as it is updated. Note that this function is only invoked when the value is updated from QML.

PySide2.QtQml.QQmlPropertyMap. value ( key ) ¶

参数

key – unicode

返回类型

object

Returns the value associated with key .

If no value has been set for this key (or if the value has been cleared), an invalid QVariant 被返回。

PySide2.QtQml.QQmlPropertyMap. valueChanged ( key , value ) ¶

参数

• key – unicode

• value – object