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<?xml version="1.0" encoding="UTF-8"?>
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<title>Qt 4.8: QML Advanced Tutorial 1 - Creating the Game Canvas and Blocks</title>
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<h3><a name="toc">Contents</a></h3>
<ul>
<li class="level2"><a href="#creating-the-application-screen">Creating the application screen</a></li>
<li class="level2"><a href="#adding-and-components">Adding <tt>Button</tt> and <tt>Block</tt> components</a></li>
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<h1 class="title">QML Advanced Tutorial 1 - Creating the Game Canvas and Blocks</h1>
<span class="subtitle"></span>
<!-- $$$declarative/tutorials/samegame/samegame1-description -->
<div class="descr"> <a name="details"></a>
<p>Files:</p>
<ul>
<li><a href="declarative-tutorials-samegame-samegame1-block-qml.html">declarative/tutorials/samegame/samegame1/Block.qml</a></li>
<li><a href="declarative-tutorials-samegame-samegame1-button-qml.html">declarative/tutorials/samegame/samegame1/Button.qml</a></li>
<li><a href="declarative-tutorials-samegame-samegame1-samegame-qml.html">declarative/tutorials/samegame/samegame1/samegame.qml</a></li>
<li><a href="declarative-tutorials-samegame-samegame1-samegame1-qmlproject.html">declarative/tutorials/samegame/samegame1/samegame1.qmlproject</a></li>
</ul>
<a name="creating-the-application-screen"></a>
<h3>Creating the application screen</h3>
<p>The first step is to create the basic QML items in your application.</p>
<p>To begin with, we create our Same Game application with a main screen like this:</p>
<p class="centerAlign"><img src="images/declarative-adv-tutorial1.png" alt="" /></p><p>This is defined by the main application file, <tt>samegame.qml</tt>, which looks like this:</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">screen</span>
<span class="name">width</span>: <span class="number">490</span>; <span class="name">height</span>: <span class="number">720</span>
<span class="type"><a href="qml-systempalette.html">SystemPalette</a></span> { <span class="name">id</span>: <span class="name">activePalette</span> }
<span class="type"><a href="qml-item.html">Item</a></span> {
<span class="name">width</span>: <span class="name">parent</span>.<span class="name">width</span>
<span class="type">anchors</span> { <span class="name">top</span>: <span class="name">parent</span>.<span class="name">top</span>; <span class="name">bottom</span>: <span class="name">toolBar</span>.<span class="name">top</span> }
<span class="type"><a href="qml-image.html">Image</a></span> {
<span class="name">id</span>: <span class="name">background</span>
<span class="name">anchors</span>.fill: <span class="name">parent</span>
<span class="name">source</span>: <span class="string">"../shared/pics/background.jpg"</span>
<span class="name">fillMode</span>: <span class="name">Image</span>.<span class="name">PreserveAspectCrop</span>
}
}
<span class="type"><a href="qml-rectangle.html">Rectangle</a></span> {
<span class="name">id</span>: <span class="name">toolBar</span>
<span class="name">width</span>: <span class="name">parent</span>.<span class="name">width</span>; <span class="name">height</span>: <span class="number">30</span>
<span class="name">color</span>: <span class="name">activePalette</span>.<span class="name">window</span>
<span class="name">anchors</span>.bottom: <span class="name">screen</span>.<span class="name">bottom</span>
<span class="type">Button</span> {
<span class="type">anchors</span> { <span class="name">left</span>: <span class="name">parent</span>.<span class="name">left</span>; <span class="name">verticalCenter</span>: <span class="name">parent</span>.<span class="name">verticalCenter</span> }
<span class="name">text</span>: <span class="string">"New Game"</span>
<span class="name">onClicked</span>: <span class="name">console</span>.<span class="name">log</span>(<span class="string">"This doesn't do anything yet..."</span>)
}
<span class="type"><a href="qml-text.html">Text</a></span> {
<span class="name">id</span>: <span class="name">score</span>
<span class="type">anchors</span> { <span class="name">right</span>: <span class="name">parent</span>.<span class="name">right</span>; <span class="name">verticalCenter</span>: <span class="name">parent</span>.<span class="name">verticalCenter</span> }
<span class="name">text</span>: <span class="string">"Score: Who knows?"</span>
}
}
}</pre>
<p>This gives you a basic game window that includes the main canvas for the blocks, a "New Game" button and a score display.</p>
<p>One item you may not recognize here is the <a href="qml-systempalette.html">SystemPalette</a> item. This provides access to the Qt system palette and is used to give the button a more native look-and-feel.</p>
<p>Notice the anchors for the <tt>Item</tt>, <tt>Button</tt> and <tt>Text</tt> elements are set using <a href="qdeclarativeintroduction.html#dot-properties">group notation</a> for readability.</p>
<a name="adding-and-components"></a>
<h3>Adding <tt>Button</tt> and <tt>Block</tt> components</h3>
<p>The <tt>Button</tt> item in the code above is defined in a separate component file named <tt>Button.qml</tt>. To create a functional button, we use the QML elements <a href="qml-text.html">Text</a> and <a href="qml-mousearea.html">MouseArea</a> inside a <a href="qml-rectangle.html">Rectangle</a>. Here is the <tt>Button.qml</tt> code:</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">container</span>
property <span class="type">string</span> <span class="name">text</span>: <span class="string">"Button"</span>
signal <span class="type">clicked</span>
<span class="name">width</span>: <span class="name">buttonLabel</span>.<span class="name">width</span> <span class="operator">+</span> <span class="number">20</span>; <span class="name">height</span>: <span class="name">buttonLabel</span>.<span class="name">height</span> <span class="operator">+</span> <span class="number">5</span>
<span class="type">border</span> { <span class="name">width</span>: <span class="number">1</span>; <span class="name">color</span>: <span class="name">Qt</span>.<span class="name">darker</span>(<span class="name">activePalette</span>.<span class="name">button</span>) }
<span class="name">smooth</span>: <span class="number">true</span>
<span class="name">radius</span>: <span class="number">8</span>
<span class="comment">// color the button with a gradient</span>
<span class="name">gradient</span>: <span class="name">Gradient</span> {
<span class="type"><a href="qml-gradientstop.html">GradientStop</a></span> {
<span class="name">position</span>: <span class="number">0.0</span>
<span class="name">color</span>: {
<span class="keyword">if</span> (<span class="name">mouseArea</span>.<span class="name">pressed</span>)
<span class="keyword">return</span> <span class="name">activePalette</span>.<span class="name">dark</span>
else
<span class="keyword">return</span> <span class="name">activePalette</span>.<span class="name">light</span>
}
}
<span class="type"><a href="qml-gradientstop.html">GradientStop</a></span> { <span class="name">position</span>: <span class="number">1.0</span>; <span class="name">color</span>: <span class="name">activePalette</span>.<span class="name">button</span> }
}
<span class="type"><a href="qml-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">onClicked</span>: <span class="name">container</span>.<span class="name">clicked</span>();
}
<span class="type"><a href="qml-text.html">Text</a></span> {
<span class="name">id</span>: <span class="name">buttonLabel</span>
<span class="name">anchors</span>.centerIn: <span class="name">container</span>
<span class="name">color</span>: <span class="name">activePalette</span>.<span class="name">buttonText</span>
<span class="name">text</span>: <span class="name">container</span>.<span class="name">text</span>
}
}</pre>
<p>This essentially defines a rectangle that contains text and can be clicked. The <a href="qml-mousearea.html">MouseArea</a> has an <tt>onClicked()</tt> handler that is implemented to emit the <tt>clicked()</tt> signal of the <tt>container</tt> when the area is clicked.</p>
<p>In Same Game, the screen is filled with small blocks when the game begins. Each block is just an item that contains an image. The block code is defined in a separate <tt>Block.qml</tt> file:</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">block</span>
<span class="type"><a href="qml-image.html">Image</a></span> {
<span class="name">id</span>: <span class="name">img</span>
<span class="name">anchors</span>.fill: <span class="name">parent</span>
<span class="name">source</span>: <span class="string">"../shared/pics/redStone.png"</span>
}
}</pre>
<p>At the moment, the block doesn't do anything; it is just an image. As the tutorial progresses we will animate and give behaviors to the blocks. We have not added any code yet to create the blocks; we will do this in the next chapter.</p>
<p>We have set the image to be the size of its parent Item using <tt>anchors.fill: parent</tt>. This means that when we dynamically create and resize the block items later on in the tutorial, the image will be scaled automatically to the correct size.</p>
<p>Notice the relative path for the Image element's <tt>source</tt> property. This path is relative to the location of the file that contains the <a href="qml-image.html">Image</a> element. Alternatively, you could set the Image source to an absolute file path or a URL that contains an image.</p>
<p>You should be familiar with the code so far. We have just created some basic elements to get started. Next, we will populate the game canvas with some blocks.</p>
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