How to get inputs value on google calendars add-on?

I am writing my firs add-on for Google Calendar and I am having troubles getting the values from input field, or date pickers.

I've created a card with couple of date pickers (event start date and end date), a text input (for events title), and a button. What I want to do is after clicking a button I would like to get the entered value of the text input and (for now) log it.

This is what I've got:

var card = CardService.newCardBuilder();
var textInputTitle = CardService.newTextInput()
    .setFieldName("text_input_title")
    .setTitle("Title for editor");

function onHomepage(e) {
  return createCard(e.hostApp, true);
}

function createCard(text) {

// Create action button for submitting entered data
  var action = CardService.newAction()
      .setFunctionName('onCreateEvent')
      .setParameters({text: text});
  var button = CardService.newTextButton()
      .setText('Create event')
      .setOnClickAction(action)
      .setTextButtonStyle(CardService.TextButtonStyle.FILLED);
  var buttonSet = CardService.newButtonSet()
      .addButton(button);

  var startDateTimePicker = CardService.newDateTimePicker()
    .setTitle("Event start date")
    .setFieldName("date_time_field_start")
    .setValueInMsSinceEpoch(new Date().getTime())
    .setTimeZoneOffsetInMins(+2 * 60)
    .setOnChangeAction(CardService.newAction()
    .setFunctionName("handleDateTimeChange"));

  var endDateTimePicker = CardService.newDateTimePicker()
    .setTitle("Event end date")
    .setFieldName("date_time_field_end")
    .setValueInMsSinceEpoch(new Date().getTime())
    .setTimeZoneOffsetInMins(+2 * 60)
    .setOnChangeAction(CardService.newAction()
    .setFunctionName("handleDateTimeChange"));


  var section = CardService.newCardSection().setHeader("I am section header")
      .addWidget(startDateTimePicker)
      .addWidget(endDateTimePicker)
      .addWidget(textInputTitle)
      .addWidget(buttonSet);

  card.addSection(section);
  return card.build();
  } 

function onCreateEvent(e){
  Logger.log("Text input%s ",JSON.stringify(e) );
}

I've tried to log the textInputs value but all I get is null. Also I checked the Google app script,gmail addon get TextInput value where a similar problem is solved, but I can't figure out where e.formInput is coming from.

UPDATE adding my manifest file

{
  "timeZone": "America/New_York",
  "dependencies": {
    "enabledAdvancedServices": [{
      "userSymbol": "Calendar",
      "serviceId": "calendar",
      "version": "v3"
    }]
  },
  "exceptionLogging": "STACKDRIVER",
  "oauthScopes": ["https://www.googleapis.com/auth/calendar.addons.execute",
                  "https://www.googleapis.com/auth/calendar", 
                  "https://www.googleapis.com/auth/script.locale"
                 ],
  "runtimeVersion": "V8",
  "addOns": {
    "common": {
      "name": "event creator",
      "logoUrl": "https://www.gstatic.com/images/icons/material/system/1x/calendar_today_black_48dp.png",
      "useLocaleFromApp": true,
      "homepageTrigger": {
        "runFunction": "onHomepage",
        "enabled": true
      }
    },
    "calendar": {
      "eventOpenTrigger": {
        "runFunction": "onCalendarEventOpen"
      }
    }
  }
}