Property bindings and assignments in QML

On QML attribute binding and Assignment property assignment

Assign a value to a property in the literal sense

Rectangle {    id:rect    Component.onCompeleted:{        10// 赋值        10// 赋值        rect.color"red"// 赋值    }}

When a property is assigned a value, a signal handler can be used to add a processing function to the signal, and for the signal processor, which is the queue that connects to the slot function of the same signal, each time the processor is written for the signal handler, it does not overwrite the last written handler. The latest processing function is added to the end of the processing queue of the signal processor, when the signal handler is triggered, according to the queue, advanced first execution. (similar to decorated mode).

Binding a property binding to an expression

Property binding allows an attribute to be bound to an expression, such as a number, a string, a function, an expression of an operation, or a block of code that has a return value.

Rectangle {    id:rect    width:10// 绑定到一个数字    height:1010//绑定到表达式    radius:{        if10return2;        elsereturn3;    // 绑定到一个代码块    color:Qt.rgba(10.90.81// 绑定到一个函数}

Binding properties via Binding

Rectangle{    id: root    width: 100    height: 100    Text{        id: showText    }    Binding{        target:id:showText // 被绑定的对象，可以是通过c++注册的单例对象        property:"text" // 通过字符串来找到属性        value: root.width // 绑定到root.width        // Binding 相当于        // bool QObject::?setProperty(const char * name, const QVariant & value);    }}

Bind by Propertychanges

Import QtQuick2. 0Item {  ID: container width:   height:  Rectangle {id:rect width: +;            height:  color: "Red" Mousearea {Id:mousearea Anchors.fill:parent  }states: State {  name: "resized"; When  : mousearea.pressed propertychanges {target:rect;  color: "Blue";  height: container.height  }        }    }}

Propertychanges generally with state to use

Use Qt.binding (function) to specify a function to bind to a property

Rectangle {    id: rect    100    100    Component.onCompeleted: {        200// 仅仅只是赋值操作        function(){                return width*1.5;            // 直接绑定到一个函数    }}

The bound expression, which contains the properties of the object, is signaled whenever the property changes, and the property of the binding expression updates itself according to the expression.

QML Core functionality-Attribute binding

Property bindings and assignments in QML