public interface HasChangeHandlers extends HasHandlers
|Modifier and Type||Method and Description|
Called when a FormItem's value is about to change as the result of user interaction.
HandlerRegistration addChangeHandler(ChangeHandler handler)
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.
Change/Changed notifications vs "...When" rules: the
changed events only fire when an end user modifies a field value. If you are trying to dynamically control
the visibility or enabled state of other components in response to these events, consider instead using properties
Canvas.enableWhen on the target component. (Similar properties are
MenuItem and other components).
handler- the change handler
HandlerRegistrationused to remove this handler