<?xml version="1.0" encoding="UTF-8"?> <!DOCTYPE html> <html lang="en"> <head> <meta http-equiv="Content-Type" content="text/html; charset=utf-8" /> <!-- tutorial.qdoc --> <title>QML Tutorial 2 - QML Components | Qt Quick 5.11</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 ><a href="../qtdoc/index.html">Qt 5.11</a></td><td ><a href="qtquick-index.html">Qt Quick</a></td><td >QML Tutorial 2 - QML Components</td></tr></table><table class="buildversion"><tr> <td id="buildversion" width="100%" align="right">Qt 5.11.2 Reference Documentation</td> </tr></table> </div> </div> <div class="content"> <div class="line"> <div class="content mainContent"> <link rel="prev" href="qml-tutorial1.html" /> <link rel="next" href="qml-tutorial3.html" /> <p class="naviNextPrevious headerNavi"> <a class="prevPage" href="qml-tutorial1.html">QML Tutorial 1 - Basic Types</a> <span class="naviSeparator"> ◦ </span> <a class="nextPage" href="qml-tutorial3.html">QML Tutorial 3 - States and Transitions</a> </p><p/> <div class="sidebar"> <div class="toc"> <h3><a name="toc">Contents</a></h3> <ul> <li class="level1"><a href="#walkthrough">Walkthrough</a></li> <li class="level2"><a href="#the-cell-component">The Cell Component</a></li> <li class="level2"><a href="#the-main-qml-file">The Main QML File</a></li> </ul> </div> <div class="sidebar-content" id="sidebar-content"></div></div> <h1 class="title">QML Tutorial 2 - QML Components</h1> <span class="subtitle"></span> <!-- $$$qml-tutorial2.html-description --> <div class="descr"> <a name="details"></a> <p>This chapter adds a color picker to change the color of the text.</p> <p class="centerAlign"><img src="images/declarative-tutorial2.png" alt="" /></p><p>Our color picker is made of six cells with different colors. To avoid writing the same code multiple times for each cell, we create a new <code>Cell</code> component. A component provides a way of defining a new type that we can re-use in other QML files. A QML component is like a black-box and interacts with the outside world through properties, signals and functions and is generally defined in its own QML file. (For more details, see the <a href="../qtqml/qml-qtqml-component.html">Component</a> documentation). The component's filename must always start with a capital letter.</p> <p>Here is the QML code for <code>Cell.qml</code>:</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> property <span class="type">alias</span> <span class="name">cellColor</span>: <span class="name">rectangle</span>.<span class="name">color</span> signal <span class="type">clicked</span>(color cellColor) <span class="name">width</span>: <span class="number">40</span>; <span class="name">height</span>: <span class="number">25</span> <span class="type"><a href="qml-qtquick-rectangle.html">Rectangle</a></span> { <span class="name">id</span>: <span class="name">rectangle</span> <span class="name">border</span>.color: <span class="string">"white"</span> <span class="name">anchors</span>.fill: <span class="name">parent</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">container</span>.<span class="name">clicked</span>(<span class="name">container</span>.<span class="name">cellColor</span>) } } </pre> <a name="walkthrough"></a> <h2 id="walkthrough">Walkthrough</h2> <a name="the-cell-component"></a> <h3 >The Cell Component</h3> <pre class="qml"> <span class="type"><a href="qml-qtquick-item.html">Item</a></span> { <span class="name">id</span>: <span class="name">container</span> property <span class="type">alias</span> <span class="name">cellColor</span>: <span class="name">rectangle</span>.<span class="name">color</span> signal <span class="type">clicked</span>(color cellColor) <span class="name">width</span>: <span class="number">40</span>; <span class="name">height</span>: <span class="number">25</span> </pre> <p>The root type of our component is an <a href="qml-qtquick-item.html">Item</a> with the <code>id</code> <i>container</i>. An <a href="qml-qtquick-item.html">Item</a> is the most basic visual type in QML and is often used as a container for other types.</p> <pre class="qml"> property <span class="type">alias</span> <span class="name">cellColor</span>: <span class="name">rectangle</span>.<span class="name">color</span> </pre> <p>We declare a <code>cellColor</code> property. This property is accessible from <i>outside</i> our component, this allows us to instantiate the cells with different colors. This property is just an alias to an existing property - the color of the rectangle that compose the cell (see <a href="../qtqml/qtqml-syntax-propertybinding.html">Property Binding</a>).</p> <pre class="qml"> signal <span class="type">clicked</span>(color cellColor) </pre> <p>We want our component to also have a signal that we call <i>clicked</i> with a <i>cellColor</i> parameter of type <i>color</i>. We will use this signal to change the color of the text in the main QML file later.</p> <pre class="qml"> <span class="type"><a href="qml-qtquick-rectangle.html">Rectangle</a></span> { <span class="name">id</span>: <span class="name">rectangle</span> <span class="name">border</span>.color: <span class="string">"white"</span> <span class="name">anchors</span>.fill: <span class="name">parent</span> } </pre> <p>Our cell component is basically a colored rectangle with the <code>id</code> <i>rectangle</i>.</p> <p>The <code>anchors.fill</code> property is a convenient way to set the size of a visual type. In this case the rectangle will have the same size as its parent (see <a href="qtquick-positioning-anchors.html">Anchor-Based Layout</a>).</p> <pre class="qml"> <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">container</span>.<span class="name">clicked</span>(<span class="name">container</span>.<span class="name">cellColor</span>) } </pre> <p>In order to change the color of the text when clicking on a cell, we create a <a href="qml-qtquick-mousearea.html">MouseArea</a> type with the same size as its parent.</p> <p>A <a href="qml-qtquick-mousearea.html">MouseArea</a> defines a signal called <i>clicked</i>. When this signal is triggered we want to emit our own <i>clicked</i> signal with the color as parameter.</p> <a name="the-main-qml-file"></a> <h3 >The Main QML File</h3> <p>In our main QML file, we use our <code>Cell</code> component to create the color picker:</p> <pre class="qml"> import QtQuick 2.0 <span class="type"><a href="qml-qtquick-rectangle.html">Rectangle</a></span> { <span class="name">id</span>: <span class="name">page</span> <span class="name">width</span>: <span class="number">320</span>; <span class="name">height</span>: <span class="number">480</span> <span class="name">color</span>: <span class="string">"lightgray"</span> <span class="type"><a href="qml-qtquick-text.html">Text</a></span> { <span class="name">id</span>: <span class="name">helloText</span> <span class="name">text</span>: <span class="string">"Hello world!"</span> <span class="name">y</span>: <span class="number">30</span> <span class="name">anchors</span>.horizontalCenter: <span class="name">page</span>.<span class="name">horizontalCenter</span> <span class="name">font</span>.pointSize: <span class="number">24</span>; <span class="name">font</span>.bold: <span class="number">true</span> } <span class="type"><a href="qml-qtquick-grid.html">Grid</a></span> { <span class="name">id</span>: <span class="name">colorPicker</span> <span class="name">x</span>: <span class="number">4</span>; <span class="name">anchors</span>.bottom: <span class="name">page</span>.<span class="name">bottom</span>; <span class="name">anchors</span>.bottomMargin: <span class="number">4</span> <span class="name">rows</span>: <span class="number">2</span>; <span class="name">columns</span>: <span class="number">3</span>; <span class="name">spacing</span>: <span class="number">3</span> <span class="type">Cell</span> { <span class="name">cellColor</span>: <span class="string">"red"</span>; <span class="name">onClicked</span>: <span class="name">helloText</span>.<span class="name">color</span> <span class="operator">=</span> <span class="name">cellColor</span> } <span class="type">Cell</span> { <span class="name">cellColor</span>: <span class="string">"green"</span>; <span class="name">onClicked</span>: <span class="name">helloText</span>.<span class="name">color</span> <span class="operator">=</span> <span class="name">cellColor</span> } <span class="type">Cell</span> { <span class="name">cellColor</span>: <span class="string">"blue"</span>; <span class="name">onClicked</span>: <span class="name">helloText</span>.<span class="name">color</span> <span class="operator">=</span> <span class="name">cellColor</span> } <span class="type">Cell</span> { <span class="name">cellColor</span>: <span class="string">"yellow"</span>; <span class="name">onClicked</span>: <span class="name">helloText</span>.<span class="name">color</span> <span class="operator">=</span> <span class="name">cellColor</span> } <span class="type">Cell</span> { <span class="name">cellColor</span>: <span class="string">"steelblue"</span>; <span class="name">onClicked</span>: <span class="name">helloText</span>.<span class="name">color</span> <span class="operator">=</span> <span class="name">cellColor</span> } <span class="type">Cell</span> { <span class="name">cellColor</span>: <span class="string">"black"</span>; <span class="name">onClicked</span>: <span class="name">helloText</span>.<span class="name">color</span> <span class="operator">=</span> <span class="name">cellColor</span> } } } </pre> <p>We create the color picker by putting 6 cells with different colors in a grid.</p> <pre class="qml"> <span class="type">Cell</span> { <span class="name">cellColor</span>: <span class="string">"red"</span>; <span class="name">onClicked</span>: <span class="name">helloText</span>.<span class="name">color</span> <span class="operator">=</span> <span class="name">cellColor</span> } </pre> <p>When the <i>clicked</i> signal of our cell is triggered, we want to set the color of the text to the <i>cellColor</i> passed as a parameter. We can react to any signal of our component through a property of the name <i>'onSignalName'</i> (see <a href="../qtqml/qtqml-syntax-objectattributes.html#signal-attributes">Signal Attributes</a>).</p> </div> <!-- @@@qml-tutorial2.html --> <p class="naviNextPrevious footerNavi"> <a class="prevPage" href="qml-tutorial1.html">QML Tutorial 1 - Basic Types</a> <span class="naviSeparator"> ◦ </span> <a class="nextPage" href="qml-tutorial3.html">QML Tutorial 3 - States and Transitions</a> </p> </div> </div> </div> </div> </div> <div class="footer"> <p> <acronym title="Copyright">©</acronym> 2018 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>