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POWhy is a dynamically by C++ generated QML Item not aware of other pre-existing Items?
 

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  1. POWhy is a dynamically by C++ generated QML Item not aware of other pre-existing Items?
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    <p>I have a <code>QQuickView</code> that displays a QML file which itself consists of several QML Items (in separate files). I'd like to add Items dynamically using C++ code. The dynamically added item should resize with the parent one, i.e. <code>width</code> and <code>height</code> properties reference parent.</p> <p>For example, my target Item in QML looks like this:</p> <pre><code>// TargetContainer.qml Grid { id: fillMeWithItemsContainer objectName: "fillMeWithItemsContainer" } </code></pre> <p>The Item I want to add dynamically (maybe multiple times) looks like this:</p> <pre><code>// DynamicItem.qml Rectangle { color: "white" height: fillMeWithItemsContainer.height width: height * 4/3 } </code></pre> <p><strong>Note that the rectangle references the container it is intended to reside in regarding height.</strong></p> <p><code>quickView</code> is populated with <code>TargetContainer</code>:</p> <pre><code>QQuickView *quickView = new QQuickView(); quickView-&gt;setSource(QUrl("qrc:/foo/bar/TargetContainer.qml")); </code></pre> <p>So I load a component</p> <pre><code>QQmlComponent dynamicallyLoadedComponent( quickView-&gt;engine(), QUrl("qrc:/foo/bar/DynamicItem.qml") ); </code></pre> <p>And I create an Object out of it.</p> <pre><code>QObject *dynamicallyLoadedObject = dynamicallyLoadedComponent.create(); </code></pre> <p><strong>Here I get an error</strong> (in application output view):</p> <pre><code>DynamicItem.qml:4: ReferenceError: fillMeWithItemsContainer is not defined </code></pre> <p><code>quickView</code> should be aware of the existence of <code>fillMeWithItemsContainer</code>, because it has been created before. However, <code>fillMeWithItemsContainer</code> is not a parent of <code>dynamicallyLoadedObject</code> (yet) and this could be the problem.</p> <p>So I find the target Item by </p> <pre><code>QQuickItem *targetItem = quickView-&gt;rootObject()-&gt;findChild&lt;QQuickItem*&gt;("fillMeWithItemsContainer"); </code></pre> <p>And reparent the previously created object</p> <pre><code>dynamicallyLoadedObject-&gt;setProperty("parent", QVariant::fromValue&lt;QObject*&gt;(targetItem )); </code></pre> <p>Note: I tried <code>dynamicallyLoadedObject-&gt;setParent()</code> before, but this seems to be a different kind of parent (<code>QObject</code> vs. parent property).</p> <p>However, the width and height properties of <code>dynamicallyLoadedObject</code> are set to 0 (because of the reference error, I assume) and won't change. Even if I set them again programatically</p> <pre><code>dynamicallyLoadedObject-&gt;setProperty("height", "fillMeWithItemsContainer.height;"); dynamicallyLoadedObject-&gt;setProperty("width", "height * 4/3"); </code></pre> <p>nothing changes.</p> <p><strong>If I define DynamicItem directly in QML it works:</strong></p> <pre><code>Grid { id: fillMeWithItemsContainer objectName: "fillMeWithItemsContainer" DynamicItem {} } </code></pre> <p>How do I make sure that dynamically added items can access Items that have been in the QML view before? Alternatively: What am I doing wrong?</p>
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