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Breadcrumbs go here --> <li>QML Tutorial 2 - QML Components</li> </ul> </div> <div class="toolbuttons toolblock"> <ul> <li id="smallA" class="t_button">A</li> <li id="medA" class="t_button active">A</li> <li id="bigA" class="t_button">A</li> <li id="print" class="t_button"><a href="javascript:this.print();"> <span>Print</span></a></li> </ul> </div> </div> <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> <a class="nextPage" href="qml-tutorial3.html">QML Tutorial 3 - States and Transitions</a> </p><p/> <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> <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 <tt>Cell</tt> 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 <a href="qmlreusablecomponents.html#defining-new-components">Defining New Components</a>). The component's filename must always start with a capital letter.</p> <p>Here is the QML code for <tt>Cell.qml</tt>:</p> <pre class="qml"> import QtQuick 1.0 <span class="type"><a href="qml-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-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-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>Walkthrough</h2> <a name="the-cell-component"></a> <h3>The Cell Component</h3> <pre class="qml"> <span class="type"><a href="qml-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 element of our component is an <a href="qml-item.html">Item</a> with the <tt>id</tt> <i>container</i>. An <a href="qml-item.html">Item</a> is the most basic visual element in QML and is often used as a container for other elements.</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 <tt>cellColor</tt> 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="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-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 <tt>id</tt> <i>rectangle</i>.</p> <p>The <tt>anchors.fill</tt> property is a convenient way to set the size of an element. In this case the rectangle will have the same size as its parent (see <a href="qml-anchor-layout.html#anchor-layout">Anchor-Based Layout</a>).</p> <pre class="qml"> <span class="type"><a href="qml-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-mousearea.html">MouseArea</a> element with the same size as its parent.</p> <p>A <a href="qml-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 <tt>Cell</tt> component to create the color picker:</p> <pre class="qml"> import QtQuick 1.0 <span class="type"><a href="qml-rectangle.html">Rectangle</a></span> { <span class="name">id</span>: <span class="name">page</span> <span class="name">width</span>: <span class="number">500</span>; <span class="name">height</span>: <span class="number">200</span> <span class="name">color</span>: <span class="string">"lightgray"</span> <span class="type"><a href="qml-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-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="qdeclarativeintroduction.html#signal-handlers">Signal Handlers</a>).</p> </div> <!-- @@@qml-tutorial2.html --> <p class="naviNextPrevious footerNavi"> <a class="prevPage" href="qml-tutorial1.html">QML Tutorial 1 - Basic Types</a> <a class="nextPage" href="qml-tutorial3.html">QML Tutorial 3 - States and Transitions</a> </p> </div> </div> </div> <div class="ft"> <span></span> </div> </div> <div class="footer"> <p> <acronym title="Copyright">©</acronym> 2013 Digia Plc and/or its subsidiaries. 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