Autocomplete Suggestions for Text Inputs

The Text Input widget lets your add-on read and react to text that users provide. You can configure these widgets to provide users automatic suggestions for input text.

The suggestions provided can come from a static list of strings you provide. Alternatively, you can build the suggestions from context, such as the text the user has already typed into the widget.

Configuring suggestions

Configuring suggestions for a text input only requires that you do the following:

  • Provide either a static list of suggestions and/or define an action with a callback function that builds that list dynamically from context.
  • Attach the suggestions list and/or action to the text input widget.

If you provide both a static list of suggestions and an action, Gmail uses the static list until the user starts entering characters, whereupon the callback function is used and the static list is ignored.

Static suggestions

To offer a static list of suggestions, you only need to do the following:

  1. Create a Suggestions object.
  2. Add each static suggestion to it using addSuggestion() or addSuggestions().
  3. Attach the Suggestions object to the widget using TextInput.setSuggestions().

The UI displays static suggestions in the order in which they were added. The UI also automatically performs case-insensitive prefix matching and filters the suggestion list as the user types characters into the widget.

Suggestion actions

If you aren't using a static suggestion list, you must define an action to build your suggestions dynamically. You can do this by following these steps:

  1. Create an Action object and associate it with an callback function you define.
  2. Call the widget's TextInput.setSuggestionsAction() function, providing it the Action object.
  3. Implement the callback function to build the suggestion list and return a built SuggestionsResponse object.

The UI calls the callback function whenever the user types a character into the text input, but only after the user has stopped typing for a moment. The callback function receives an event object containing information about the open card's widgets. See the Action guide for details on the event object structure.

The callback function must return a valid SuggestionsResponse object containing the list of suggestions to display. The UI displays suggestions in the order that they are added. Unlike static lists, the UI does not conduct any automatic filtering of callback suggestions based on the user input. If you want to have such filtering, you must read the text input value from the event object and filter your suggestions as you construct the list.


The following code snippet shows how to configure suggestions on two different text input widgets, the first with a static list and the second using a callback function:

// Create an input with a static suggestion list.
var textInput1 = CardService.newTextInput()
    .setTitle('Color choice')
        .addSuggestions(['Blue', 'Black', 'Green']));

// Create an input with a dynamic suggestion list.
var action = CardService.newAction()
var textInput2 = CardService.newTextInput()

// ...

 *  Build and return a suggestion response. In this case, the suggested
 *  emails are taken from the To: and CC: lists of the open message
 *  in Gmail, filtered by the text that the user has already entered.
 *  @param {Object} e the event object containing data associated with
 *      this text input widget.
 *  @returns {SuggestionsResponse}
 function refreshSuggestions(e) {
   // Activate temporary Gmail add-on scopes, in this case so that the
   // open message metadata can be read.
   var accessToken = e.messageMetadata.accessToken;

   var userInput = e && e.formInput['emailInput'].toLowerCase();
   var messageId = e.messageMetadata.messageId;
   var message = GmailApp.getMessageById(messageId);

   // Combine the comma-separated returned by these methods.
   var addresses = message.getTo() + ',' + message.getCc();

   // Filter the address list to those containing the text the user
   // has already entered.
   var suggestionList = [];
   addresses.split(',').forEach(function(email) {
     if (email.toLowerCase().indexOf(userInput) !== -1) {

   return CardService.newSuggestionsResponseBuilder()
       .build();  // Don't forget to build the response!

Suggestions and OnChangeAction()

Text input widgets can have a setOnChangeAction() handler function defined that executes whenever the widget loses focus. If this handler and suggestions are both enabled for the same text input, the following rules define the text input interaction behavior:

  1. The setOnChangeAction() handler executes after a suggestion is selected.
  2. If the user presses Enter (or otherwise makes the text input lose focus) without modifying the selected suggestion, setOnChangeAction() does not trigger again.
  3. setOnChangeAction() does trigger again if the user, after selecting a suggestion, edits it so that it no longer matches any of the suggestions in the list.
  4. If the user does not select a suggestion, setOnChangeAction() triggers when the text input loses focus.