<?xml version="1.0" encoding="UTF-8"?> <!DOCTYPE html> <html lang="en"> <head> <meta http-equiv="Content-Type" content="text/html; charset=utf-8" /> <!-- qquickpropertychanges.cpp --> <title>PropertyChanges QML Type | Qt Quick 5.9</title> <link rel="stylesheet" type="text/css" href="style/offline-simple.css" /> <script type="text/javascript"> document.getElementsByTagName("link").item(0).setAttribute("href", "style/offline.css"); // loading style sheet breaks anchors that were jumped to before // so force jumping to anchor again setTimeout(function() { var anchor = location.hash; // need to jump to different anchor first (e.g. none) location.hash = "#"; setTimeout(function() { location.hash = anchor; }, 0); }, 0); </script> </head> <body> <div class="header" id="qtdocheader"> <div class="main"> <div class="main-rounded"> <div class="navigationbar"> <table><tr> <td >Qt 5.9</td><td ><a href="qtquick-index.html">Qt Quick</a></td><td ><a href="qtquick-qmlmodule.html">QML Types</a></td><td >PropertyChanges QML Type</td></tr></table><table class="buildversion"><tr> <td id="buildversion" width="100%" align="right">Qt 5.9.4 Reference Documentation</td> </tr></table> </div> </div> <div class="content"> <div class="line"> <div class="content mainContent"> <div class="sidebar"> <div class="toc"> <h3><a name="toc">Contents</a></h3> <ul> <li class="level1"><a href="#properties">Properties</a></li> <li class="level1"><a href="#details">Detailed Description</a></li> <li class="level2"><a href="#resetting-property-values">Resetting Property Values</a></li> <li class="level2"><a href="#immediate-property-changes-in-transitions">Immediate Property Changes in Transitions</a></li> </ul> </div> <div class="sidebar-content" id="sidebar-content"></div></div> <h1 class="title">PropertyChanges QML Type</h1> <span class="subtitle"></span> <!-- $$$PropertyChanges-brief --> <p>Describes new property bindings or values for a state. <a href="#details">More...</a></p> <!-- @@@PropertyChanges --> <div class="table"><table class="alignedsummary"> <tr><td class="memItemLeft rightAlign topAlign"> Import Statement:</td><td class="memItemRight bottomAlign"> import QtQuick 2.7</td></tr></table></div><ul> <li><a href="qml-qtquick-propertychanges-members.html">List of all members, including inherited members</a></li> </ul> <a name="properties"></a> <h2 id="properties">Properties</h2> <ul> <li class="fn"><b><b><a href="qml-qtquick-propertychanges.html#explicit-prop">explicit</a></b></b> : bool</li> <li class="fn"><b><b><a href="qml-qtquick-propertychanges.html#restoreEntryValues-prop">restoreEntryValues</a></b></b> : bool</li> <li class="fn"><b><b><a href="qml-qtquick-propertychanges.html#target-prop">target</a></b></b> : Object</li> </ul> <!-- $$$PropertyChanges-description --> <a name="details"></a> <h2 id="details">Detailed Description</h2> <p><a href="qml-qtquick-propertychanges.html">PropertyChanges</a> is used to define the property values or bindings in a <a href="qml-qtquick-state.html">State</a>. This enables an item's property values to be changed when it <a href="qtquick-statesanimations-states.html">changes between states</a>.</p> <p>To create a <a href="qml-qtquick-propertychanges.html">PropertyChanges</a> object, specify the <a href="qml-qtquick-propertychanges.html#target-prop">target</a> item whose properties are to be modified, and define the new property values or bindings. For example:</p> <pre class="qml"> import QtQuick 2.0 <span class="type"><a href="qml-qtquick-item.html">Item</a></span> { <span class="name">id</span>: <span class="name">container</span> <span class="name">width</span>: <span class="number">300</span>; <span class="name">height</span>: <span class="number">300</span> <span class="type"><a href="qml-qtquick-rectangle.html">Rectangle</a></span> { <span class="name">id</span>: <span class="name">rect</span> <span class="name">width</span>: <span class="number">100</span>; <span class="name">height</span>: <span class="number">100</span> <span class="name">color</span>: <span class="string">"red"</span> <span class="type"><a href="qml-qtquick-mousearea.html">MouseArea</a></span> { <span class="name">id</span>: <span class="name">mouseArea</span> <span class="name">anchors</span>.fill: <span class="name">parent</span> } <span class="name">states</span>: <span class="name">State</span> { <span class="name">name</span>: <span class="string">"resized"</span>; <span class="name">when</span>: <span class="name">mouseArea</span>.<span class="name">pressed</span> <span class="type"><a href="qml-qtquick-propertychanges.html">PropertyChanges</a></span> { <span class="name">target</span>: <span class="name">rect</span>; <span class="name">color</span>: <span class="string">"blue"</span>; <span class="name">height</span>: <span class="name">container</span>.<span class="name">height</span> } } } } </pre> <p>When the mouse is pressed, the <a href="qml-qtquick-rectangle.html">Rectangle</a> changes to the <i>resized</i> state. In this state, the <a href="qml-qtquick-propertychanges.html">PropertyChanges</a> object sets the rectangle's color to blue and the <code>height</code> value to that of <code>container.height</code>.</p> <p>Note this automatically binds <code>rect.height</code> to <code>container.height</code> in the <i>resized</i> state. If a property binding should not be established, and the height should just be set to the value of <code>container.height</code> at the time of the state change, set the <a href="qml-qtquick-propertychanges.html#explicit-prop">explicit</a> property to <code>true</code>.</p> <p>A <a href="qml-qtquick-propertychanges.html">PropertyChanges</a> object can also override the default signal handler for an object to implement a signal handler specific to the new state:</p> <pre class="qml"> <span class="type"><a href="qml-qtquick-propertychanges.html">PropertyChanges</a></span> { <span class="name">target</span>: <span class="name">myMouseArea</span> <span class="name">onClicked</span>: <span class="name">doSomethingDifferent</span>() } </pre> <p><b>Note: </b><a href="qml-qtquick-propertychanges.html">PropertyChanges</a> can be used to change anchor margins, but not other anchor values; use <a href="qml-qtquick-anchorchanges.html">AnchorChanges</a> for this instead. Similarly, to change an <a href="qml-qtquick-item.html">Item</a>'s <a href="qml-qtquick-item.html#parent-prop">parent</a> value, use <a href="qml-qtquick-parentchange.html">ParentChange</a> instead.</p><a name="resetting-property-values"></a> <h3 >Resetting Property Values</h3> <p>The <code>undefined</code> value can be used to reset the property value for a state. In the following example, when <code>myText</code> changes to the <i>widerText</i> state, its <code>width</code> property is reset, giving the text its natural width and displaying the whole string on a single line.</p> <pre class="qml"> <span class="type"><a href="qml-qtquick-rectangle.html">Rectangle</a></span> { <span class="name">width</span>: <span class="number">300</span>; <span class="name">height</span>: <span class="number">200</span> <span class="type"><a href="qml-qtquick-text.html">Text</a></span> { <span class="name">id</span>: <span class="name">myText</span> <span class="name">width</span>: <span class="number">50</span> <span class="name">wrapMode</span>: <span class="name">Text</span>.<span class="name">WordWrap</span> <span class="name">text</span>: <span class="string">"a text string that is longer than 50 pixels"</span> <span class="name">states</span>: <span class="name">State</span> { <span class="name">name</span>: <span class="string">"widerText"</span> <span class="type"><a href="qml-qtquick-propertychanges.html">PropertyChanges</a></span> { <span class="name">target</span>: <span class="name">myText</span>; <span class="name">width</span>: <span class="name">undefined</span> } } } <span class="type"><a href="qml-qtquick-mousearea.html">MouseArea</a></span> { <span class="name">anchors</span>.fill: <span class="name">parent</span> <span class="name">onClicked</span>: <span class="name">myText</span>.<span class="name">state</span> <span class="operator">=</span> <span class="string">"widerText"</span> } } </pre> <a name="immediate-property-changes-in-transitions"></a> <h3 >Immediate Property Changes in Transitions</h3> <p>When <a href="qtquick-statesanimations-animations.html">Transitions</a> are used to animate state changes, they animate properties from their values in the current state to those defined in the new state (as defined by <a href="qml-qtquick-propertychanges.html">PropertyChanges</a> objects). However, it is sometimes desirable to set a property value <i>immediately</i> during a <a href="qmlexampletoggleswitch.html#transition">Transition</a>, without animation; in these cases, the <a href="qml-qtquick-propertyaction.html">PropertyAction</a> type can be used to force an immediate property change.</p> <p>See the <a href="qml-qtquick-propertyaction.html">PropertyAction</a> documentation for more details.</p> <p><b>Note: </b>The <a href="qml-qtquick-item.html#visible-prop">visible</a> and <a href="qml-qtquick-item.html#enabled-prop">enabled</a> properties of <a href="qml-qtquick-item.html">Item</a> do not behave exactly the same as other properties in <a href="qml-qtquick-propertychanges.html">PropertyChanges</a>. Since these properties can be changed implicitly through their parent's state, they should be set explicitly in all <a href="qml-qtquick-propertychanges.html">PropertyChanges</a>. An item will still not be enabled/visible if one of its parents is not enabled or visible.</p><p><b>See also </b><a href="qtquick-animation-example.html#states">States example</a>, <a href="qtquick-statesanimations-states.html">Qt Quick States</a>, and Qt QML.</p> <!-- @@@PropertyChanges --> <h2>Property Documentation</h2> <!-- $$$explicit --> <div class="qmlitem"><div class="qmlproto"> <div class="table"><table class="qmlname"> <tr valign="top" class="odd" id="explicit-prop"> <td class="tblQmlPropNode"><p> <a name="explicit-prop"></a><span class="name">explicit</span> : <span class="type">bool</span></p></td></tr> </table></div> </div><div class="qmldoc"><p>If explicit is set to true, any potential bindings will be interpreted as once-off assignments that occur when the state is entered.</p> <p>In the following example, the addition of explicit prevents <code>myItem.width</code> from being bound to <code>parent.width</code>. Instead, it is assigned the value of <code>parent.width</code> at the time of the state change.</p> <pre class="qml"> <span class="type"><a href="qml-qtquick-propertychanges.html">PropertyChanges</a></span> { <span class="name">target</span>: <span class="name">myItem</span> <span class="name">explicit</span>: <span class="number">true</span> <span class="name">width</span>: <span class="name">parent</span>.<span class="name">width</span> } </pre> <p>By default, explicit is false.</p> </div></div><!-- @@@explicit --> <br/> <!-- $$$restoreEntryValues --> <div class="qmlitem"><div class="qmlproto"> <div class="table"><table class="qmlname"> <tr valign="top" class="odd" id="restoreEntryValues-prop"> <td class="tblQmlPropNode"><p> <a name="restoreEntryValues-prop"></a><span class="name">restoreEntryValues</span> : <span class="type">bool</span></p></td></tr> </table></div> </div><div class="qmldoc"><p>This property holds whether the previous values should be restored when leaving the state.</p> <p>The default value is <code>true</code>. Setting this value to <code>false</code> creates a temporary state that has permanent effects on property values.</p> </div></div><!-- @@@restoreEntryValues --> <br/> <!-- $$$target --> <div class="qmlitem"><div class="qmlproto"> <div class="table"><table class="qmlname"> <tr valign="top" class="odd" id="target-prop"> <td class="tblQmlPropNode"><p> <a name="target-prop"></a><span class="name">target</span> : <span class="type">Object</span></p></td></tr> </table></div> </div><div class="qmldoc"><p>This property holds the object which contains the properties to be changed.</p> </div></div><!-- @@@target --> <br/> </div> </div> </div> </div> </div> <div class="footer"> <p> <acronym title="Copyright">©</acronym> 2017 The Qt Company Ltd. Documentation contributions included herein are the copyrights of their respective owners.<br> The documentation provided herein is licensed under the terms of the <a href="http://www.gnu.org/licenses/fdl.html">GNU Free Documentation License version 1.3</a> as published by the Free Software Foundation.<br> Qt and respective logos are trademarks of The Qt Company Ltd. in Finland and/or other countries worldwide. All other trademarks are property of their respective owners. </p> </div> </body> </html>