com.smartgwt.client.widgets.form.fields.events

## Interface ChangeHandler

- All Superinterfaces:
    EventHandler

      public interface ChangeHandler
      extends EventHandler

- - ### Method Summary

    Methods
    Modifier and Type | Method and Description
    --- | ---
    `void` | `onChange(ChangeEvent event)` Called when a FormItem's value is about to change as the result of user interaction.

- - ### Method Detail

    - #### onChange

          void onChange(ChangeEvent event)

      Called when a FormItem's value is about to change as the result of user interaction. This method fires after the user performed an action that would change the value of this field, but before the element itself is changed.

      Returning false cancels the change. Note that if what you want to do is transform the user's input, for example, automatically change separator characters to a standard separator character, you should implement `transformInput` rather than using a combination of change() and setValue() to accomplish the same thing. Returning false from `change` is intended for rejecting input entirely, such as typing invalid characters.

      Note that if you ask the form for the current value in this handler, you will get the old value because the change has not yet been committed. The new value is available as a parameter to this method.

      Parameters:
        `event` - the event