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<td ><a href="index.html">Qt 5.9</a></td><td >Use Case - Responding To User Input in QML</td></tr></table><table class="buildversion"><tr>
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<h3><a name="toc">Contents</a></h3>
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<li class="level1"><a href="#supported-types-of-user-input">Supported Types of User Input</a></li>
<li class="level2"><a href="#mouse-and-touch-events">Mouse and Touch Events</a></li>
<li class="level2"><a href="#keyboard-and-button-events">Keyboard and Button Events</a></li>
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<h1 class="title">Use Case - Responding To User Input in QML</h1>
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<a name="supported-types-of-user-input"></a>
<h2 id="supported-types-of-user-input">Supported Types of User Input</h2>
<p>The Qt Quick module provides support for the most common types of user input, including mouse and touch events, text input and key-press events. Other modules provide support for other types of user input (for example, the Qt Sensors module provides support for shake-gestures in QML applications).</p>
<p>This article covers how to handle basic user input; for further information about motion-gesture support, please see the Qt Sensors documentation. For information about audio-visual input, please see the Qt Multimedia documentation.</p>
<a name="mouse-and-touch-events"></a>
<h3 >Mouse and Touch Events</h3>
<p>The MouseArea type allows mouse and touch events to be handled in a QML application. A MouseArea can be combined with either an Image or a Rectangle and <a href="whatsnew50.html#text">Text</a> object to implement a simple button.</p>
<pre class="qml">
import QtQuick 2.3
<span class="type">Item</span> {
<span class="name">id</span>: <span class="name">root</span>
<span class="name">width</span>: <span class="number">320</span>
<span class="name">height</span>: <span class="number">480</span>
<span class="type">Rectangle</span> {
<span class="name">color</span>: <span class="string">"#272822"</span>
<span class="name">width</span>: <span class="number">320</span>
<span class="name">height</span>: <span class="number">480</span>
}
<span class="type">Rectangle</span> {
<span class="name">id</span>: <span class="name">rectangle</span>
<span class="name">x</span>: <span class="number">40</span>
<span class="name">y</span>: <span class="number">20</span>
<span class="name">width</span>: <span class="number">120</span>
<span class="name">height</span>: <span class="number">120</span>
<span class="name">color</span>: <span class="string">"red"</span>
<span class="type">MouseArea</span> {
<span class="name">anchors</span>.fill: <span class="name">parent</span>
<span class="name">onClicked</span>: <span class="name">rectangle</span>.<span class="name">width</span> <span class="operator">+=</span> <span class="number">10</span>
}
}
}
</pre>
<p>For more advanced use cases requiring multiple touch points, please read the documentation for the MultiPointTouchArea type and the PinchArea type.</p>
<p>Note that some types have their own built in input handling. For example, Flickable responds to mouse dragging, mouse wheel scrolling, touch dragging, and touch flicking by default.</p>
<a name="keyboard-and-button-events"></a>
<h3 >Keyboard and Button Events</h3>
<p>Button and key presses, from buttons on a device, a keypad, or a keyboard, can all be handled using the Keys attached property. This attached property is available on all Item derived types, and works with the Item::focus property to determine which type receives the key event. For simple key handling, you can set the focus to true on a single Item and do all your key handling there.</p>
<pre class="qml">
import QtQuick 2.3
<span class="type">Item</span> {
<span class="name">id</span>: <span class="name">root</span>
<span class="name">width</span>: <span class="number">320</span>
<span class="name">height</span>: <span class="number">480</span>
<span class="type">Rectangle</span> {
<span class="name">color</span>: <span class="string">"#272822"</span>
<span class="name">width</span>: <span class="number">320</span>
<span class="name">height</span>: <span class="number">480</span>
}
<span class="type">Rectangle</span> {
<span class="name">id</span>: <span class="name">rectangle</span>
<span class="name">x</span>: <span class="number">40</span>
<span class="name">y</span>: <span class="number">20</span>
<span class="name">width</span>: <span class="number">120</span>
<span class="name">height</span>: <span class="number">120</span>
<span class="name">color</span>: <span class="string">"red"</span>
<span class="name">focus</span>: <span class="number">true</span>
<span class="name">Keys</span>.onUpPressed: <span class="name">rectangle</span>.<span class="name">y</span> <span class="operator">-=</span> <span class="number">10</span>
<span class="name">Keys</span>.onDownPressed: <span class="name">rectangle</span>.<span class="name">y</span> <span class="operator">+=</span> <span class="number">10</span>
<span class="name">Keys</span>.onLeftPressed: <span class="name">rectangle</span>.<span class="name">x</span> <span class="operator">+=</span> <span class="number">10</span>
<span class="name">Keys</span>.onRightPressed: <span class="name">rectangle</span>.<span class="name">x</span> <span class="operator">-=</span> <span class="number">10</span>
}
}
</pre>
<p>For text input the Qt Quick module provides several built-in types. In particular, the TextInput and TextEdit types allow for single-line entry and multi-line editing respectively.</p>
<p>Here is all you need to get a working TextInput:</p>
<pre class="cpp">
import <span class="type">QtQuick</span> <span class="number">2.3</span>
TextInput {
focus: <span class="keyword">true</span>
text: <span class="string">"Initial Text"</span>
}
</pre>
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