help view arcgis flex

good day someone could help me? I want to insert the view in a flex arcgis <s:panel> but I get the following error window WidgetManager (Error # 2036)
I want to insert this code in a <s:panel>

<s: Application xmlns: fx = "http://ns.adobe.com/mxml/2009"
xmlns: s = "library :/ / ns.adobe.com / flex / spark"
xmlns: viewer = "com.esri.viewer. *"
xmlns: managers = "com.esri.viewer.managers. *"
pageTitle = "ArcGIS Viewer for Flex">


<fx:Metadata>
[ResourceBundle ("ViewerStrings")]
</ fx: Metadata>

<viewer:ViewerContainer id="viewerContainer">
<viewer:configManager>
<managers:ConfigManager id="configManager"/>
</ viewer: ConfigManager>
<viewer:dataManager>
<managers:DataManager id="dataManager"/>
</ viewer: DataManager>
<viewer:mapManager>
<managers:MapManager id="mapManager"/>
</ viewer: MapManager>
<viewer:uiManager>
<managers:UIManager id="uiManager"/>
</ viewer: UIManager>
<viewer:widgetManager>
<managers:WidgetManager id="widgetManager"/>
</ viewer: WidgetManager>
</ viewer: ViewerContainer>

</ s: Application>

Currently only shows me the map but does not show me any tools.