How to show suggestions in a GWT SuggestBox only after 2 characters have been typed?

Question

I am trying to make a SuggestBox showing suggestions only after 2 characters have been typed. My idea was to hide the suggestions when the text length is 1, using the class DefaultSuggestionDisplay. I have tried to attach different handlers like KeyPressHandler and KeyUpHandler on the SuggestionBox itself and its TextBox, but none of them seemed to work. Do you have any "suggestions"? :D

Answer 1

You can extend DefaultSuggestionDisplay and override showSuggestions method:

public class MySuggestionDisplay extends DefaultSuggestionDisplay {
    @Override
    protected void showSuggestions(SuggestBox suggestBox, Collection<? extends Suggestion> suggestions, boolean isDisplayStringHTML, boolean isAutoSelectEnabled, SuggestionCallback callback) {
        if(suggestBox.getText().length() > 1)
            super.showSuggestions(suggestBox, suggestions, isDisplayStringHTML, isAutoSelectEnabled, callback);
    }
}

You have to pass your new display to the SuggestBox constructor:

public class MySuggestBox extends SuggestBox {
    public MySuggestBox() {
        super(
            new MySuggestOracle(),
            new TextBox(), 
            new MySuggestionDisplay());
    }
}

In this constructor you should provide:

• your own SuggestOracle class (here named MySuggestOracle) - I suppose you have one
• TextBox - it is the default widget to enter text (you can provide your own, it just needs to implement HasText)
• SuggestionDisplay - use the one with showSuggestions method overridden.

---

This is full working example code showing suggestions on at least 2 characters typed:

import java.util.ArrayList;
import java.util.Collection;

import com.google.gwt.user.client.ui.SuggestBox;
import com.google.gwt.user.client.ui.SuggestOracle;
import com.google.gwt.user.client.ui.SuggestOracle.Suggestion;
import com.google.gwt.user.client.ui.TextBox;

public class MySuggestBox extends SuggestBox {

    public MySuggestBox() {
        super(
            new SuggestOracle() {
                @Override
                public void requestSuggestions(Request request, Callback callback) {
                    ArrayList<Suggestion> suggestions = new ArrayList<Suggestion>();
                    suggestions.add(new MySuggestion("aaa"));
                    suggestions.add(new MySuggestion("bbb"));
                    suggestions.add(new MySuggestion("ccc"));
                    suggestions.add(new MySuggestion("ddd"));

                    Response response = new Response();
                    response.setSuggestions(suggestions);
                    callback.onSuggestionsReady(request, response);
                }
            }, 
            new TextBox(), 
            new MySuggestionDisplay());
    }

    public static class MySuggestionDisplay extends DefaultSuggestionDisplay {
        @Override
        protected void showSuggestions(SuggestBox suggestBox, Collection<? extends Suggestion> suggestions, boolean isDisplayStringHTML, boolean isAutoSelectEnabled, SuggestionCallback callback) {
            if(suggestBox.getText().length() > 1)
                super.showSuggestions(suggestBox, suggestions, isDisplayStringHTML, isAutoSelectEnabled, callback);
        }
    }

    public static class MySuggestion implements Suggestion {

        private String text;

        public MySuggestion(String text) {
            this.text = text;
        }

        @Override
        public String getDisplayString() {
            return text;
        }

        @Override
        public String getReplacementString() {
            return text;
        }
    }
}

Answer 2

You can extend SuggestBox and override showSuggestionList() method.

Adding KeyUpHandler is not working because you add another KeyUpHandler, not replacing the one that SuggestBox added to its own TextBox.

EDIT:

@Override
showSuggestionList() {
    if (getTextBox().getValue().length() > 1) {
        super.showSuggestionList();
    }
}