TokenViewer – Basics
January 29th, 2009 by Eugene Ostroukhov

I created a new viewer that I think may be really useful. I’m writing this post to provide a high-level description. You can use it as follows:


<p>final TokenViewer tokenViewer = new TokenViewer(root);</p>


<p>new GridData(GridData.FILL_HORIZONTAL));</p>

<p>tokenViewer.setContentProvider(new BaseWorkbenchContentProvider());</p>

<p>tokenViewer.setLabelProvider(new WorkbenchLabelProvider());</p>



The result is a simple text field with following services:

  1. Content assist.
  2. Object-oriented IStructuredSelection support – if the user enters proper string the selection event is thrown. If user sets selection – string will appear in the text entry.
  3. Easy and familiar programming model – I guess any JFace/Eclipse plugin developer wrote dozens of those label/content providers.


TokenViewer working with workspace

TokenViewer working with workspace

This simple API works for the case when text in the text field is the same as a label in the content assist pop-up. But once you want to have different text (i.e. SSN entry may show employee name in the pop-up) you will need something more specific for this task and that is why I defined special content provider (I still hope it is easier to use then regular JFace content assist API):


<p>public interface ITokenContentProvider extends IStructuredContentProvider {</p>

<p>Object fromString(Object parent, String value);</p>

<p>String toString(Object object);</p>

<p>Object[] getChildren(Object object, String prefix);</p>


  • fromString method will return a child of the given parent node that corresponds to a specific string. It may return null.
  • toString will convert given object to its string representation.
  • getChildren tries to find all the elements that correspond to given string.

If the viewer is provided with IStructuredContentProvider (or ITreeContentProvider) it will wrap it with a custom adapter so you can use your existing code.

The label provider is used to decorate the content assist pop-up. I also have a slightly extended label provider interface:


<p>public interface IDescriptionProvider extends ILabelProvider {</p>

<p>public String getDescription(Object element);</p>


This optional extension provides the way to provide extended object descriptions that are shown along the content assist pop-up:

This is also a tokenviewer

This is also a tokenviewer

Note – red squiggles are automatically shown when there is no object that corresponds to a text.

What I’m going to implement next is:

  1. Multiple selection support when token list is separated with some delimeter.
  2. Rich text (HTML?) support both for content assist pop-up and description pop-up.

2 Responses  
  • Prakash writes:
    January 29th, 20097:44 amat

    Eugene, The token viewer with workspace contents is interesting. I like this!

    I would like to try it. Where do I get the code? If you could attach it to the bug it would reach a wider audience I guess.
    • zzhou writes:
      January 29th, 200910:52 amat

      I will cleanup the code through the weekend and then will publish it in a bug.

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