为 SWT 应用程序配备内容助理

public IContentAssistant getContentAssistant(SourceViewer sourceViewer) {
   // Create content assistant
   ContentAssistant assistant = new ContentAssistant();
   
   // Create content assistant processor
   IContentAssistProcessor processor = new HtmlContentAssistProcessor();
   
   // Set this processor for each supported content type
   assistant.setContentAssistProcessor(processor, XMLPartitionScanner.XML_TAG);
   assistant.setContentAssistProcessor(processor, XMLPartitionScanner.XML_DEFAULT);
   assistant.setContentAssistProcessor(processor, IDocument.DEFAULT_CONTENT_TYPE);
         
   // Return the content assistant   
   return assistant;
}

public ICompletionProposal[] computeCompletionProposals(ITextViewer viewer, 
   int documentOffset) {
   // Retrieve current document
   IDocument doc = viewer.getDocument();
   // Retrieve current selection range
   Point selectedRange = viewer.getSelectedRange();

   List propList = new ArrayList();

   if (selectedRange.y > 0) {
     try {
       // Retrieve selected text
       String text = doc.get(selectedRange.x, selectedRange.y);
       // Compute completion proposals
       computeStyleProposals(text, selectedRange, propList);
     } catch (BadLocationException e) {
     }
   } else {

     // Retrieve qualifier
     String qualifier = getQualifier(doc, documentOffset);
     // Compute completion proposals
     computeStructureProposals(qualifier, documentOffset, propList);
   }

   // Create completion proposal array
   ICompletionProposal[] proposals = new ICompletionProposal[propList.size()];
   // and fill with list elements
   propList.toArray(proposals);
   // Return the proposals
   return proposals; 
}

private String getQualifier(IDocument doc, int documentOffset) {
   // Use string buffer to collect characters
   StringBuffer buf = new StringBuffer();
   while (true) {
     try {
       // Read character backwards
       char c = doc.getChar(--documentOffset);
       // This was not the start of a tag
       if (c == '>' || Character.isWhitespace(c))
          return "";
       // Collect character
       buf.append(c);
       // Start of tag. Return qualifier
       if (c == '<')
           return buf.reverse().toString();
     } catch (BadLocationException e) {
       // Document start reached, no tag found
       return "";
     }
   }
}

// Proposal part before cursor
private final static String[] STRUCTTAGS1 =
   new String[] { "<P>", "<A SRC=\"", "<TABLE>",  "<TR>",  "<TD>" };
// Proposal part after cursor
private final static String[] STRUCTTAGS2 =
   new String[] { "",    "\"></A>",   "</TABLE>", "</TR>", "</TD>" }

private void computeStructureProposals(String qualifier, int documentOffset, List propList) { 
   int qlen = qualifier.length();
   // Loop through all proposals
   for (int i = 0; i < STRUCTTAGS1.length; i++) {
      String startTag = STRUCTTAGS1[i];
      // Check if proposal matches qualifier
      if (startTag.startsWith(qualifier)) {
         // Yes -- compute whole proposal text
         String text = startTag + STRUCTTAGS2[i];
         // Derive cursor position
         int cursor = startTag.length();
         // Construct proposal
         CompletionProposal proposal =
            new CompletionProposal(text, documentOffset - qlen, qlen, cursor);
         // and add to result list
         propList.add(proposal);
      }
   }
}

private final static String[] STYLETAGS = new String[] { 
      "b", "i", "code", "strong" 
};
private final static String[] STYLELABELS = new String[] { 
      "bold", "italic", "code", "strong" 
};

private void computeStyleProposals(String selectedText, Point selectedRange, List propList) {
   // Loop through all styles
   for (int i = 0; i < STYLETAGS.length; i++) {
      String tag = STYLETAGS[i];
      // Compute replacement text
      String replacement = "<" + tag + ">" + selectedText + "</" + tag + ">";
      // Derive cursor position
      int cursor = tag.length()+2;
      // Compute a suitable context information
      IContextInformation contextInfo = 
         new ContextInformation(null, STYLELABELS[i]+" Style");
      // Construct proposal
      CompletionProposal proposal = new CompletionProposal(replacement, 
         selectedRange.x, selectedRange.y, cursor, null, STYLELABELS[i], 
         contextInfo, replacement);
      // and add to result list
      propList.add(proposal);
   }
}

assistant.setInformationControlCreator(getInformationControlCreator(sourceViewer));

public IInformationControlCreator getInformationControlCreator
      (ISourceViewer sourceViewer) {
   return new IInformationControlCreator() {
      public IInformationControl createInformationControl(Shell parent) {
         return new DefaultInformationControl(parent);
      }
   };
}

   return new DefaultInformationControl(parent, presenter);

private static final DefaultInformationControl.IInformationPresenter
   presenter = new DefaultInformationControl.IInformationPresenter() {
      public String updatePresentation(Display display, String infoText,
         TextPresentation presentation, int maxWidth, int maxHeight) {
         int start = -1;
         // Loop over all characters of information text
         for (int i = 0; i < infoText.length(); i++) {
            switch (infoText.charAt(i)) {
               case '<' :
                  // Remember start of tag
                  start = i;
                  break;
               case '>' :
                  if (start >= 0) {
                    // We have found a tag and create a new style range
                    StyleRange range = 
                       new StyleRange(start, i - start + 1, null, null, SWT.BOLD)
                    // Add this style range to the presentation
                    presentation.addStyleRange(range);
                    // Reset tag start indicator
                    start = -1;
                  }
                  break;
         }
      }
      // Return the information text
      return infoText;
   }
};

public IContextInformationValidator getContextInformationValidator() {
   return new ContextInformationValidator(this);
}

public IContextInformation[] computeContextInformation(ITextViewer viewer, 
      int documentOffset) {
   // Retrieve selected range
   Point selectedRange = viewer.getSelectedRange();
   if (selectedRange.y > 0) {
      // Text is selected. Create a context information array.
      ContextInformation[] contextInfos = new ContextInformation[STYLELABELS.length];
      // Create one context information item for each style
      for (int i = 0; i < STYLELABELS.length; i++)
         contextInfos[i] = new ContextInformation(null, STYLELABELS[i]+" Style");
      return contextInfos;
   }
   return new ContextInformation[0];
}

sourceViewer.appendVerifyKeyListener(
   new VerifyKeyListener() {
      public void verifyKey(VerifyEvent event) {
      // Check for Ctrl+Spacebar
      if (event.stateMask == SWT.CTRL && event.character == ' ') {
        // Check if source viewer is able to perform operation
        if (sourceViewer.canDoOperation(SourceViewer.CONTENTASSIST_PROPOSALS))
          // Perform operation
          sourceViewer.doOperation(SourceViewer.CONTENTASSIST_PROPOSALS);
        // Veto this key press to avoid further processing
        event.doit = false;
      }
   }
});

private static final String CONTENTASSIST_PROPOSAL_ID = 
   "com.bdaum.HTMLeditor.ContentAssistProposal"; 
protected void createActions() {
   super.createActions();
   // This action will fire a CONTENTASSIST_PROPOSALS operation
   // when executed
   IAction action = 
      new TextOperationAction(SampleHTMLEditorPlugin.getDefault().getResourceBundle(),
      "ContentAssistProposal", this, SourceViewer.CONTENTASSIST_PROPOSALS);
   action.setActionDefinitionId(CONTENTASSIST_PROPOSAL_ID);
   // Tell the editor about this new action
   setAction(CONTENTASSIST_PROPOSAL_ID, action);
   // Tell the editor to execute this action 
   // when Ctrl+Spacebar is pressed
   setActionActivationCode(CONTENTASSIST_PROPOSAL_ID,' ', -1, SWT.CTRL);
}

public char[] getCompletionProposalAutoActivationCharacters() {
   return new char[] { '<' };
}

   assistant.enableAutoActivation(true);
   assistant.setAutoActivationDelay(500);

   Color bgColor = colorManager.getColor(new RGB(230,255,230));
   assistant.setProposalSelectorBackground(bgColor);