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

Interface HasChangeHandlers

All Superinterfaces:

com.google.gwt.event.shared.HasHandlers

All Known Implementing Classes:

AutoFitTextAreaItem, BlurbItem, BooleanItem, ButtonItem, CancelItem, CanvasItem, CheckboxItem, ColorItem, ColorPickerItem, ComboBoxItem, DateItem, DateRangeItem, DateTimeItem, DoubleItem, FileItem, FloatItem, FormItem, HeaderItem, HiddenItem, IntegerItem, IPickTreeItem, LinkItem, MiniDateRangeItem, MultiComboBoxItem, MultiFileItem, MultiPickerItem, NativeCheckboxItem, PasswordItem, PickTreeItem, PresetCriteriaItem, PresetDateRangeItem, RadioGroupItem, RelativeDateItem, ResetItem, RichTextItem, RowSpacerItem, SavedSearchItem, SectionItem, SelectItem, SelectOtherItem, SetFilterItem, ShuttleItem, SliderItem, SpacerItem, SpinnerItem, StaticTextItem, SubmitItem, TextAreaItem, TextItem, TimeItem, ToggleItem, ToolbarItem, UploadItem, ViewFileItem

public interface HasChangeHandlers
extends com.google.gwt.event.shared.HasHandlers

Method Summary

Modifier and Type	Method and Description
com.google.gwt.event.shared.HandlerRegistration	addChangeHandler(ChangeHandler handler) Called when a FormItem's value is about to change as the result of user interaction.

Methods inherited from interface com.google.gwt.event.shared.HasHandlers

fireEvent

Method Detail

addChangeHandler

com.google.gwt.event.shared.HandlerRegistration addChangeHandler(ChangeHandler handler)

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.

Change/Changed notifications vs "...When" rules: the change and 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 such as Canvas.visibleWhen, item.readOnlyWhen, Canvas.enableWhen on the target component. (Similar properties are available on FormItem, Canvas, MenuItem and other components).

Parameters:

handler - the change handler

Returns:

HandlerRegistration used to remove this handler