<!DOCTYPE html><html lang="en"><head><meta charset="utf-8"><meta http-equiv="X-UA-Compatible" content="IE=edge"><meta name="viewport" content="width=device-width, height=device-height, initial-scale=1, user-scalable=no"><meta name="description" content="API docs for the build method from the BackButton class, for the Dart programming language."><title>build method - BackButton class - material library - Dart API</title><!-- required because all the links are pseudo-absolute --><base href="../.."><link href="https://fonts.googleapis.com/css?family=Source+Code+Pro:500,400i,400,300|Source+Sans+Pro:400,300,700" rel="stylesheet"><link href="https://fonts.googleapis.com/icon?family=Material+Icons" rel="stylesheet"><link rel="stylesheet" href="static-assets/github.css"><link rel="stylesheet" href="static-assets/styles.css"><link rel="icon" href="static-assets/favicon.png"></head><body><div id="overlay-under-drawer"></div><header id="title"><button id="sidenav-left-toggle" type="button"> </button><ol class="breadcrumbs gt-separated dark hidden-xs"><li><a href="index.html">flutter</a></li><li><a href="material/material-library.html">material</a></li><li><a href="material/BackButton-class.html">BackButton</a></li><li class="self-crumb">build method</li></ol><div class="self-name">build</div><form class="search navbar-right" role="search"><input type="text" id="search-box" autocomplete="off" disabled class="form-control typeahead" placeholder="Loading search..."></form></header><main><div id="dartdoc-sidebar-left" class="col-xs-6 col-sm-3 col-md-2 sidebar sidebar-offcanvas-left"><header id="header-search-sidebar" class="hidden-l"><form class="search-sidebar" role="search"><input type="text" id="search-sidebar" autocomplete="off" disabled class="form-control typeahead" placeholder="Loading search..."></form></header><ol class="breadcrumbs gt-separated dark hidden-l" id="sidebar-nav"><li><a href="index.html">flutter</a></li><li><a href="material/material-library.html">material</a></li><li><a href="material/BackButton-class.html">BackButton</a></li><li class="self-crumb">build method</li></ol><h5>BackButton class</h5><ol><li class="section-title"><a href="material/BackButton-class.html#constructors">Constructors</a></li><li><a href="material/BackButton/BackButton.html">BackButton</a></li><li class="section-title"><a href="material/BackButton-class.html#instance-properties">Properties</a></li><li><a href="material/BackButton/color.html">color</a></li><li class="inherited"><a href="dart-core/Object/hashCode.html">hashCode</a></li><li class="inherited"><a href="widgets/Widget/key.html">key</a></li><li class="inherited"><a href="dart-core/Object/runtimeType.html">runtimeType</a></li><li class="section-title"><a href="material/BackButton-class.html#instance-methods">Methods</a></li><li><a href="material/BackButton/build.html">build</a></li><li class="inherited"><a href="widgets/StatelessWidget/createElement.html">createElement</a></li><li class="inherited"><a href="foundation/DiagnosticableTree/debugDescribeChildren.html">debugDescribeChildren</a></li><li class="inherited"><a href="widgets/Widget/debugFillProperties.html">debugFillProperties</a></li><li class="inherited"><a href="dart-core/Object/noSuchMethod.html">noSuchMethod</a></li><li class="inherited"><a href="foundation/DiagnosticableTree/toDiagnosticsNode.html">toDiagnosticsNode</a></li><li class="inherited"><a href="foundation/DiagnosticableMixin/toString.html">toString</a></li><li class="inherited"><a href="foundation/DiagnosticableTree/toStringDeep.html">toStringDeep</a></li><li class="inherited"><a href="foundation/DiagnosticableTree/toStringShallow.html">toStringShallow</a></li><li class="inherited"><a href="widgets/Widget/toStringShort.html">toStringShort</a></li><li class="section-title inherited"><a href="material/BackButton-class.html#operators">Operators</a></li><li class="inherited"><a href="dart-core/Object/operator_equals.html">operator ==</a></li></ol></div><!--/.sidebar-offcanvas--><div id="dartdoc-main-content" class="col-xs-12 col-sm-9 col-md-8 main-content"><div><h1><span class="kind-method">build</span> method</h1></div><section class="multi-line-signature"><div><ol class="annotation-list"><li>@override</li></ol></div><span class="returntype"><a href="widgets/Widget-class.html">Widget</a></span><span class="name ">build</span>(<wbr><span class="parameter" id="build-param-context"><span class="type-annotation"><a href="widgets/BuildContext-class.html">BuildContext</a></span> <span class="parameter-name">context</span></span>)<div class="features">override</div></section><section class="desc markdown"><p>Describes the part of the user interface represented by this widget.</p><p>The framework calls this method when this widget is inserted into thetree in a given <a href="widgets/BuildContext-class.html">BuildContext</a> and when the dependencies of this widgetchange (e.g., an <a href="widgets/InheritedWidget-class.html">InheritedWidget</a> referenced by this widget changes).</p><p>The framework replaces the subtree below this widget with the widgetreturned by this method, either by updating the existing subtree or byremoving the subtree and inflating a new subtree, depending on whether thewidget returned by this method can update the root of the existingsubtree, as determined by calling <a href="widgets/Widget/canUpdate.html">Widget.canUpdate</a>.</p><p>Typically implementations return a newly created constellation of widgetsthat are configured with information from this widget's constructor andfrom the given <a href="widgets/BuildContext-class.html">BuildContext</a>.</p><p>The given <a href="widgets/BuildContext-class.html">BuildContext</a> contains information about the location in thetree at which this widget is being built. For example, the contextprovides the set of inherited widgets for this location in the tree. Agiven widget might be built with multiple different <a href="widgets/BuildContext-class.html">BuildContext</a>arguments over time if the widget is moved around the tree or if thewidget is inserted into the tree in multiple places at once.</p><p>The implementation of this method must only depend on:</p><ul><li>the fields of the widget, which themselves must not change over time,and</li><li>any ambient state obtained from the <code>context</code> using<a href="widgets/BuildContext/inheritFromWidgetOfExactType.html">BuildContext.inheritFromWidgetOfExactType</a>.</li></ul><p>If a widget's <a href="material/BackButton/build.html">build</a> method is to depend on anything else, use a<a href="widgets/StatefulWidget-class.html">StatefulWidget</a> instead.</p><p>See also:</p><ul><li><a href="widgets/StatelessWidget-class.html">StatelessWidget</a>, which contains the discussion on performance considerations.</li></ul></section><section class="summary source-code" id="source"><h2><span>Implementation</span></h2><pre class="language-dart"><code class="language-dart">@overrideWidget build(BuildContext context) {assert(debugCheckHasMaterialLocalizations(context));return IconButton(icon: const BackButtonIcon(),color: color,tooltip: MaterialLocalizations.of(context).backButtonTooltip,onPressed: () {Navigator.maybePop(context);},);}</code></pre></section></div> <!-- /.main-content --><div id="dartdoc-sidebar-right" class="col-xs-6 col-sm-6 col-md-2 sidebar sidebar-offcanvas-right"></div><!--/.sidebar-offcanvas--></main><footer><span class="no-break">flutter 0.0.0-unknown</span></footer><script src="https://ajax.googleapis.com/ajax/libs/jquery/3.2.1/jquery.min.js"></script><script src="static-assets/typeahead.bundle.min.js"></script><script src="static-assets/highlight.pack.js"></script><script src="static-assets/URI.js"></script><script src="static-assets/script.js"></script></body></html>
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