204 lines
11 KiB
HTML
204 lines
11 KiB
HTML
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<!DOCTYPE html>
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<html lang="en">
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<head>
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<meta charset="utf-8">
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<meta http-equiv="X-UA-Compatible" content="IE=edge">
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<meta name="viewport" content="width=device-width, initial-scale=1">
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<meta name="description" content="API docs for the setState method from the SideBarContentState class, for the Dart programming language.">
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<title>setState method - SideBarContentState class - SideBarContent library - Dart API</title>
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<!-- required because all the links are pseudo-absolute -->
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<base href="../..">
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<link href="https://fonts.googleapis.com/css?family=Source+Code+Pro:500,400i,400,300|Source+Sans+Pro:400,300,700" rel="stylesheet">
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<link rel="stylesheet" href="static-assets/github.css">
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<link rel="stylesheet" href="static-assets/styles.css">
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<link rel="icon" href="static-assets/favicon.png">
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</head>
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<body>
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<div id="overlay-under-drawer"></div>
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<header id="title">
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<button id="sidenav-left-toggle" type="button"> </button>
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<ol class="breadcrumbs gt-separated dark hidden-xs">
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<li><a href="index.html">touch_demonstrator</a></li>
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<li><a href="pages_SideBarContent/pages_SideBarContent-library.html">SideBarContent</a></li>
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<li><a href="pages_SideBarContent/SideBarContentState-class.html">SideBarContentState</a></li>
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<li class="self-crumb">setState method</li>
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</ol>
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<div class="self-name">setState</div>
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<form class="search navbar-right" role="search">
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<input type="text" id="search-box" autocomplete="off" disabled class="form-control typeahead" placeholder="Loading search...">
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</form>
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</header>
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<main>
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<div class="col-xs-6 col-sm-3 col-md-2 sidebar sidebar-offcanvas-left">
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<h5>SideBarContentState class</h5>
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<ol>
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<li class="section-title"><a href="pages_SideBarContent/SideBarContentState-class.html#constructors">Constructors</a></li>
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<li><a href="pages_SideBarContent/SideBarContentState/SideBarContentState.html">SideBarContentState</a></li>
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<li class="section-title inherited">
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<a href="pages_SideBarContent/SideBarContentState-class.html#instance-properties">Properties</a>
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</li>
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<li class="inherited"><a href="pages_SideBarContent/SideBarContentState/context.html">context</a></li>
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<li class="inherited"><a href="pages_SideBarContent/SideBarContentState/hashCode.html">hashCode</a></li>
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<li class="inherited"><a href="pages_SideBarContent/SideBarContentState/mounted.html">mounted</a></li>
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<li class="inherited"><a href="pages_SideBarContent/SideBarContentState/runtimeType.html">runtimeType</a></li>
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<li class="inherited"><a href="pages_SideBarContent/SideBarContentState/widget.html">widget</a></li>
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<li class="section-title"><a href="pages_SideBarContent/SideBarContentState-class.html#instance-methods">Methods</a></li>
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<li><a href="pages_SideBarContent/SideBarContentState/build.html">build</a></li>
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<li class="inherited"><a href="pages_SideBarContent/SideBarContentState/deactivate.html">deactivate</a></li>
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<li class="inherited"><a href="pages_SideBarContent/SideBarContentState/debugFillProperties.html">debugFillProperties</a></li>
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<li class="inherited"><a href="pages_SideBarContent/SideBarContentState/didChangeDependencies.html">didChangeDependencies</a></li>
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<li class="inherited"><a href="pages_SideBarContent/SideBarContentState/didUpdateWidget.html">didUpdateWidget</a></li>
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<li class="inherited"><a href="pages_SideBarContent/SideBarContentState/dispose.html">dispose</a></li>
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<li class="inherited"><a href="pages_SideBarContent/SideBarContentState/initState.html">initState</a></li>
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<li class="inherited"><a href="pages_SideBarContent/SideBarContentState/noSuchMethod.html">noSuchMethod</a></li>
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<li class="inherited"><a href="pages_SideBarContent/SideBarContentState/reassemble.html">reassemble</a></li>
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<li class="inherited"><a href="pages_SideBarContent/SideBarContentState/setState.html">setState</a></li>
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<li class="inherited"><a href="pages_SideBarContent/SideBarContentState/toDiagnosticsNode.html">toDiagnosticsNode</a></li>
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<li class="inherited"><a href="pages_SideBarContent/SideBarContentState/toString.html">toString</a></li>
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<li class="inherited"><a href="pages_SideBarContent/SideBarContentState/toStringShort.html">toStringShort</a></li>
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<li class="section-title inherited"><a href="pages_SideBarContent/SideBarContentState-class.html#operators">Operators</a></li>
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<li class="inherited"><a href="pages_SideBarContent/SideBarContentState/operator_equals.html">operator ==</a></li>
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</ol>
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</div><!--/.sidebar-offcanvas-->
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<div class="col-xs-12 col-sm-9 col-md-8 main-content">
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<h1>setState method</h1>
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<section class="multi-line-signature">
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<div>
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<ol class="annotation-list">
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<li>@protected</li>
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</ol>
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</div>
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<span class="returntype">void</span>
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<span class="name ">setState</span>
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(<wbr><span class="parameter" id="setState-param-fn"><span class="type-annotation">VoidCallback</span> <span class="parameter-name">fn</span></span>)
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<div class="features">@protected, inherited</div>
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</section>
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<section class="desc markdown">
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<p>Notify the framework that the internal state of this object has changed.</p>
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<p>Whenever you change the internal state of a <code>State</code> object, make the
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change in a function that you pass to <a href="pages_SideBarContent/SideBarContentState/setState.html">setState</a>:</p>
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<pre class="language-dart"><code class="language-dart">setState(() { _myState = newValue });
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</code></pre>
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<p>The provided callback is immediately called synchronously. It must not
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return a future (the callback cannot be <code>async</code>), since then it would be
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unclear when the state was actually being set.</p>
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<p>Calling <a href="pages_SideBarContent/SideBarContentState/setState.html">setState</a> notifies the framework that the internal state of this
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object has changed in a way that might impact the user interface in this
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subtree, which causes the framework to schedule a <a href="pages_SideBarContent/SideBarContentState/build.html">build</a> for this <code>State</code>
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object.</p>
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<p>If you just change the state directly without calling <a href="pages_SideBarContent/SideBarContentState/setState.html">setState</a>, the
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framework might not schedule a <a href="pages_SideBarContent/SideBarContentState/build.html">build</a> and the user interface for this
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subtree might not be updated to reflect the new state.</p>
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<p>Generally it is recommended that the <code>setState</code> method only be used to
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wrap the actual changes to the state, not any computation that might be
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associated with the change. For example, here a value used by the <a href="pages_SideBarContent/SideBarContentState/build.html">build</a>
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function is incremented, and then the change is written to disk, but only
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the increment is wrapped in the <code>setState</code>:</p>
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<pre class="language-dart"><code class="language-dart">Future<void> _incrementCounter() async {
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setState(() {
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_counter++;
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});
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Directory directory = await getApplicationDocumentsDirectory();
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final String dirName = directory.path;
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await File('$dir/counter.txt').writeAsString('$_counter');
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}
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</code></pre>
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<p>It is an error to call this method after the framework calls <a href="pages_SideBarContent/SideBarContentState/dispose.html">dispose</a>.
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You can determine whether it is legal to call this method by checking
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whether the <a href="pages_SideBarContent/SideBarContentState/mounted.html">mounted</a> property is true.</p>
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</section>
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<section class="summary source-code" id="source">
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<h2><span>Implementation</span> </h2>
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<pre class="language-dart"><code class="language-dart">@protected
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void setState(VoidCallback fn) {
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assert(fn != null);
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assert(() {
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if (_debugLifecycleState == _StateLifecycle.defunct) {
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throw FlutterError(
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'setState() called after dispose(): $this\n'
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'This error happens if you call setState() on a State object for a widget that '
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'no longer appears in the widget tree (e.g., whose parent widget no longer '
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'includes the widget in its build). This error can occur when code calls '
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'setState() from a timer or an animation callback. The preferred solution is '
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'to cancel the timer or stop listening to the animation in the dispose() '
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'callback. Another solution is to check the "mounted" property of this '
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'object before calling setState() to ensure the object is still in the '
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'tree.\n'
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'This error might indicate a memory leak if setState() is being called '
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'because another object is retaining a reference to this State object '
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'after it has been removed from the tree. To avoid memory leaks, '
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'consider breaking the reference to this object during dispose().'
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);
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}
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if (_debugLifecycleState == _StateLifecycle.created && !mounted) {
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throw FlutterError(
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'setState() called in constructor: $this\n'
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'This happens when you call setState() on a State object for a widget that '
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'hasn\'t been inserted into the widget tree yet. It is not necessary to call '
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'setState() in the constructor, since the state is already assumed to be dirty '
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'when it is initially created.'
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);
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}
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return true;
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}());
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final dynamic result = fn() as dynamic;
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assert(() {
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if (result is Future) {
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throw FlutterError(
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'setState() callback argument returned a Future.\n'
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'The setState() method on $this was called with a closure or method that '
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'returned a Future. Maybe it is marked as "async".\n'
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'Instead of performing asynchronous work inside a call to setState(), first '
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'execute the work (without updating the widget state), and then synchronously '
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'update the state inside a call to setState().'
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);
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}
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// We ignore other types of return values so that you can do things like:
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// setState(() => x = 3);
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return true;
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}());
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_element.markNeedsBuild();
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}</code></pre>
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</section>
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</div> <!-- /.main-content -->
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<div class="col-xs-6 col-sm-6 col-md-2 sidebar sidebar-offcanvas-right">
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</div><!--/.sidebar-offcanvas-->
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</main>
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<footer>
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<span class="no-break">
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touch_demonstrator 1.0.0+1
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</span>
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</footer>
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<script src="https://ajax.googleapis.com/ajax/libs/jquery/3.2.1/jquery.min.js"></script>
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<script src="static-assets/typeahead.bundle.min.js"></script>
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<script src="static-assets/highlight.pack.js"></script>
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<script src="static-assets/URI.js"></script>
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<script src="static-assets/script.js"></script>
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</body>
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</html>
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