uibinder - GWT 2.5.1: dynamic required field indicator -

what better approach displaying dynamic required field indicator (in case, display '*' next field if empty, hide if user type something, display again if user clears input field) ? indicator called requiredfieldhighlight in code below.

myvalueboxeditordecorator.java

public class myvalueboxeditordecorator<t> extends composite implements haseditorerrors<t>, iseditor<valueboxeditor<t>> {     interface binder extends uibinder<widget, myvalueboxeditordecorator<?>>     {         binder binder = gwt.create(binder.class);     }      @uifield     divelement label;      @uifield     simplepanel contents;      @uifield     divelement requiredfieldhighlight;      @uifield     divelement errorlabel;      private valueboxeditor<t> editor;      private valueboxbase<t> valuebox;      /**      * constructs valueboxeditordecorator.      */     @uiconstructor     public myvalueboxeditordecorator()     {         initwidget(binder.binder.createandbindui(this));     }      public myvalueboxeditordecorator(int dummy)     {         this();          valuebox = (valueboxbase<t>) new textboxtest(requiredfieldhighlight);         this.editor = valuebox.aseditor();           valuebox.addvaluechangehandler(new valuechangehandler<t>()                 {             @override             public void onvaluechange(valuechangeevent<t> event)             {                 myvalueboxeditordecorator.this.onvaluechange();             }                 });          contents.add(valuebox);          myvalueboxeditordecorator.this.onvaluechange();     }      private void onvaluechange()     {         t value = editor.getvalue();          if (value == null)         {             requiredfieldhighlight.getstyle().setdisplay(style.display.inline_block);             return;         }         else         {             requiredfieldhighlight.getstyle().setdisplay(style.display.none);         }     }      public valueboxeditor<t> aseditor()     {         return editor;     }       public void seteditor(valueboxeditor<t> editor)     {         this.editor = editor;     }      @uichild(limit = 1, tagname = "valuebox")     public void setvaluebox(valueboxbase<t> widget)     {         contents.add(widget);         seteditor(widget.aseditor());     }      @override     public void showerrors(list<editorerror> errors)     {         // manages content of errorlabel uifield     } } 

uibinder file:

<ui:uibinder xmlns:ui='urn:ui:com.google.gwt.uibinder'     xmlns:g='urn:import:com.google.gwt.user.client.ui'>      <ui:style src="common.css" />      <g:htmlpanel width="100%">         <div ui:field="label"  class="{style.label}"/>         <g:simplepanel ui:field="contents" styleprimaryname="{style.contents}" />         <div class="{style.errorlabel}" ui:field="errorlabel" />         <div class="{style.errorlabel} {style.requiredfieldhighlight}" ui:field="requiredfieldhighlight">*</div>     </g:htmlpanel> </ui:uibinder> 

the issue approach onvaluechange() not called when screen initialized (before user interacts widget), although need myvalueboxeditordecorator update status of 'requiredfieldhighlight' ! why created textboxtest class. pass reference indicator divelement object , overload settext+setvalue.

textboxtest.java

public class textboxtest extends textbox {     @override     public void settext(string text)     {         super.settext(text);         updaterequiredfieldhighlight(text);     }      private final divelement requiredfieldhighlight;      public textboxtest(divelement requiredfieldhighlight)     {         super();         this.requiredfieldhighlight = requiredfieldhighlight;     }      private void updaterequiredfieldhighlight(string withvalue)     {         if (withvalue != null && !withvalue.isempty())         {             requiredfieldhighlight.getstyle().setdisplay(style.display.none);         }         else         {             requiredfieldhighlight.getstyle().setdisplay(style.display.inline_block);         }     }       @override     public void setvalue(string value, boolean fireevents)     {         super.setvalue(value, fireevents);         updaterequiredfieldhighlight(value);     } } 

i have several problems approach. first, creates dependency specific class of mine (textboxtest), , second, not work because settext() not automagically called gwt when clear contents of text field using gui ! in other words indicator work properly, need both overload settext+setvalue in textboxtest class and have valuechangehandler added myvalueboxeditordecorator object. why ? (and right event / place handle text change ?)

20150629 update: setvalue() called when screen initialized. valuechangehandler not triggered, 'though, due gwt internals (i think due setvalue() provided without fireevents flag calling fireevents overload false fireevent flag).