Package org.patternfly.handler

package org.patternfly.handler

Common event handler interfaces used throughout PatternFly Java components.

This package defines functional interfaces for handling various component events in a type-safe manner. All handlers follow a consistent pattern: they accept a DOM event, the component that triggered the event, and event-specific data. Components register these handlers using on<Event>() methods.

Handler Interfaces

• ComponentHandler - Generic handler accepting a component
• ChangeHandler - Handler for value change events with old and new values
• SelectHandler - Handler for selection events with selected state
• MultiSelectHandler - Handler for multi-selection events with list of selected items
• ToggleHandler - Handler for expand/collapse toggle events
• CloseHandler - Handler for close/dismiss events
• ResizeHandler - Handler for resize events with dimensions

Usage Examples

Change Handler

Handle value changes in form components:

TextInput input = textInput("username")
    .onChange((event, component, value) -> {
        console.log("Username changed to: " + value);
        validateUsername(value);
    });

Selection Handler

Respond to selection events in lists and tables:

DataList<User> dataList = dataList(dataProvider)
    .onSelect((event, item, selected) -> {
        console.log("User " + item.name() + " selected: " + selected);
    });

Toggle Handler

Handle expand/collapse state in expandable components:

Drawer drawer = drawer()
    .onToggle((event, component, expanded) -> {
        console.log("Drawer expanded: " + expanded);
        if (expanded) {
            loadDrawerContent();
        }
    });

Close Handler

Perform cleanup when components are closed:

Alert alert = alert("Success", "Operation completed")
    .onClose((event, component) -> {
        console.log("Alert dismissed");
        removeFromDOM(component);
    });

Handler Registration Pattern

Components follow a consistent pattern for registering handlers. Methods are named on<Event>() and return the component to enable method chaining:

Switch switch_ = switch_("enable-feature")
    .value(false)
    .onChange((e, c, value) -> console.log("Switch: " + value))
    .onToggle((e, c, checked) -> updateFeatureState(checked));

Functional Interface Benefits

All handler interfaces are marked with @FunctionalInterface, enabling:

• Lambda expressions for concise event handling
• Method references for even more compact code
• Type safety with compile-time checking
• Clear IDE support with parameter hints

See Also:

• Handler API Documentation

Interfaces

Class	Description
ChangeHandler<C,T>	Functional interface for handling change events.
CloseHandler<C>
ComponentHandler<C>
MultiSelectHandler<C,T>
ResizeHandler<C>	Functional interface for handling resize.
SelectHandler<C>
ToggleHandler<C>