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<h1>Naming and Element finding</h1>
<p>Naming a UI component is used to find an element by a unique name
in UI structure tree. This concept is used both in Java class by
programming and in XML via Control Binding concept.</p>
<p>The name must be in unique in a scope, named as &quot;Named
scope&quot;. The named scope corresponds with an XWT resource file.</p>
<h2>Finding in Java</h2>
<p>XWT uses x:Name property or Name property to name a component.
This section will show how to name an element and how to find an element
by its name in Java class.</p>
<p>In the example below, we will create a Label named Message and a
Button.</p>
<p>XAML:</p>
<pre>
<span class="XMLElementTag">&lt;Shell</span> <span class="XMLAttrTag">xmlns</span>=<span
class="XMLAttrValue">"http://www.eclipse.org/xwt/presentation"</span>
&nbsp;&nbsp;&nbsp;&nbsp;<span class="XMLAttrTag">xmlns:x</span>=<span
class="XMLAttrValue">"http://www.eclipse.org/xwt"</span>
&nbsp;&nbsp;&nbsp;&nbsp;<span class="XMLAttrTag">x:Class</span>=<span
class="XMLAttrValue">"org.eclipse.xwt.tests.name.Name_x"</span>
&nbsp;&nbsp;&nbsp;&nbsp;<span class="XMLAttrTag">text</span>=<span
class="XMLAttrValue">"NameT test"</span><span class="XMLElementTag">&gt;</span>
&nbsp;&nbsp;&nbsp;&nbsp;<span class="XMLElementTag">&lt;Shell.layout&gt;</span>
&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;<span
class="XMLElementTag">&lt;GridLayout</span> <span class="XMLAttrTag">numColumns</span>=<span
class="XMLAttrValue">"2"</span> <span class="XMLElementTag">/&gt;</span>
&nbsp;&nbsp;&nbsp;&nbsp;<span class="XMLElementTag">&lt;/Shell.layout&gt;</span>
&nbsp;&nbsp;&nbsp;&nbsp;<span class="XMLElementTag">&lt;Label</span> <span
class="XMLAttrTag">Name</span>=<span class="XMLAttrValue">"Message"</span> <span
class="XMLElementTag">/&gt;</span>
&nbsp;&nbsp;&nbsp;&nbsp;<span class="XMLElementTag">&lt;Button</span> <span
class="XMLAttrTag">SelectionEvent</span>=<span class="XMLAttrValue">"handleButton"</span> <span
class="XMLAttrTag">Text</span>=<span class="XMLAttrValue">"Click Here"</span> <span
class="XMLElementTag">/&gt;</span>
<span class="XMLElementTag">&lt;/Shell&gt;</span>
</pre>
<p>Consider the example above, the Label gets a name "Message", and
set the contents of the button with string "Click Here". Then we add an
event handling here by SelectionEvent property and named the event
"handleButton". In the rendered window, when we click the button, the
handleButton tries to find the Label. If it works, dialog "Name works"
will pop-up. Otherwise, an error dialog "Label message is not found"
will open instead. Please see the Java code below.</p>
<p>Java:</p>
<pre>
<span class="JavaKeyword">protected void</span> handleButton(Event event) {
&nbsp;&nbsp;&nbsp;&nbsp;Label message = (Label) XWT.findElementByName(event.widget, "Message");
&nbsp;&nbsp;&nbsp;&nbsp;<span class="JavaKeyword">if</span> (message == null) {
&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;MessageDialog.openError(XWT.findShell(event.<span
class="JavaMember">widget</span>), <span class="JavaString">"Test Name"</span>, <span
class="JavaString">"Label message is not found"</span>);
&nbsp;&nbsp;&nbsp;&nbsp;} <span class="JavaKeyword">else</span> {
&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;MessageDialog.openInformation(XWT.findShell(event.<span
class="JavaMember">widget</span>), <span class="JavaString">"Test Name"</span>, <span
class="JavaString">"Name works."</span>);
&nbsp;&nbsp;&nbsp;&nbsp;}
}
</pre>
<p>The first argument of findElementByName() indicates the start
point of search. Precisely, the search starts with its NamedScope. If
the name is not find in the current NamedScope, the search will proceed
in its parent NamedScope. The &quot;null&quot; will be returned if the
name is not found in the entire tree structure.<br>
</p>
<h2>Element Finding</h2>
<p>In XWT XML, an element also can be found by its name. It mostly
used in control binding. Control binding is used to establish a
connection among two or more UI elements.</p>
<pre>
<span class="XMLElementTag">&lt;Shell</span> <span class="XMLAttrTag">xmlns</span>=<span
class="XMLAttrValue">"http://www.eclipse.org/xwt/presentation"</span>
&nbsp;&nbsp;&nbsp;&nbsp;<span class="XMLAttrTag">xmlns:x</span>=<span
class="XMLAttrValue">"http://www.eclipse.org/xwt"</span>
&nbsp;&nbsp;&nbsp;&nbsp;<span class="XMLAttrTag">x:Class</span>=<span
class="XMLAttrValue">"org.eclipse.xwt.tests.layout.FormLayout_Test"</span><span
class="XMLElementTag">&gt;</span>
&nbsp;&nbsp;&nbsp;&nbsp;<span class="XMLElementTag">&lt;Shell.layout&gt;</span>
&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;<span
class="XMLElementTag">&lt;FormLayout /&gt;</span>
&nbsp;&nbsp;&nbsp;&nbsp;<span class="XMLElementTag">&lt;/Shell.layout&gt;</span>
&nbsp;&nbsp;&nbsp;&nbsp;<span class="XMLElementTag">&lt;Group</span> <span
class="XMLAttrTag">text</span>=<span class="XMLAttrValue">"layout"</span><span
class="XMLElementTag">&gt;</span>
&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;<span
class="XMLElementTag">&lt;Group.layout&gt;</span>
&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;<span
class="XMLElementTag">&lt;FormLayout /&gt;</span>
&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;<span
class="XMLElementTag">&lt;/Group.layout&gt;</span>
&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;<span
class="XMLElementTag">&lt;Group.layoutData&gt;</span>
&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;<span
class="XMLElementTag">&lt;GridData</span> <span class="XMLAttrTag">horizontalAlignment</span>=<span
class="XMLAttrValue">"FILL"</span> <span class="XMLAttrTag">verticalAlignment</span>=<span
class="XMLAttrValue">"FILL"</span><span class="XMLElementTag">&gt;</span>
&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;<span
class="XMLElementTag">&lt;/GridData&gt;</span>
&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;<span
class="XMLElementTag">&lt;/Group.layoutData&gt;</span>
&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;<span
class="XMLElementTag">&lt;Button</span> <span class="XMLAttrTag">x:Name</span>=<span
class="XMLAttrValue">"Button1"</span> <span class="XMLAttrTag">text</span>=<span
class="XMLAttrValue">"button1"</span><span class="XMLElementTag">&gt;</span>
&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;<span
class="XMLElementTag">&lt;Button.layout&gt;</span>
&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;<span
class="XMLElementTag">&lt;FormData</span> <span class="XMLAttrTag">top</span>=<span
class="XMLAttrValue">"10, 10"</span> <span class="XMLAttrTag">left</span>=<span
class="XMLAttrValue">"0, 10"</span> <span class="XMLAttrTag">bottom</span>=<span
class="XMLAttrValue">"30, 0"</span> <span class="XMLAttrTag">right</span>=<span
class="XMLAttrValue">"40, 0"</span> <span class="XMLElementTag">/&gt;</span>
&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;<span
class="XMLElementTag">&lt;/Button.layout&gt;</span>
&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;<span
class="XMLElementTag">&lt;/Button&gt;</span>
&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;<span
class="XMLElementTag">&lt;Button</span> <span class="XMLAttrTag">text</span>=<span
class="XMLAttrValue">"button2"</span><span class="XMLElementTag">&gt;</span>
&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;<span
class="XMLElementTag">&lt;Button.layout&gt;</span>
&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;<span
class="XMLElementTag">&lt;FormData</span> <span class="XMLAttrTag">top</span>=<span
class="XMLAttrValue">"{Binding ElementName=Button1}, 10"</span> <span
class="XMLAttrTag">left</span>=<span class="XMLAttrValue">"0, 0"</span>
&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;<span
class="XMLAttrTag">bottom</span>=<span class="XMLAttrValue">"40, 0"</span> <span
class="XMLAttrTag">right</span>=<span class="XMLAttrValue">"40, 0"</span> <span
class="XMLElementTag">/&gt;</span>
&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;<span
class="XMLElementTag">&lt;/Button.layout&gt;</span>
&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;<span
class="XMLElementTag">&lt;/Button&gt;</span>
&nbsp;&nbsp;&nbsp;&nbsp;<span class="XMLElementTag">&lt;/Group&gt;</span>
<span class="XMLElementTag">&lt;/Shell&gt;</span>
</pre>
<p>Consider the above example, it start to search from <tt>top="{Binding
ElementName=Button1}</tt>, it try to find the element named <tt>Button1</tt>
in the current NamedScope, if not found, the search will proceed in its
parent NamedScope. If the element is exist in the tree structure and it
has the correct settings. the <tt>top</tt> property of the second button
synchronized with <tt>Button1</tt>, Or the code will show error.</p>
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