GWT%20Interview%20Questions%20and%20Answers

Question: How to make GWT Custom Event Handler?

Answer: This is an event that is triggered when the user becomes happy.

Define a new event class. You can add arbitrary metadata in the event class. For simplicity, we will not include any here though.

public class HappyEvent extends GwtEvent {
...
}
Define a new handler and marker interface for the event class.

interface HappyHandler extends EventHandler {
public void onHappiness(HappyEvent event);
}

interface HasHappyEvents {
public HandlerRegistration addHappyHandler(HappyHandler handler);
}
Add a unique event type

class HappyEvent extends AbstractEvent{
public static AbstractEvent.Key KEY = new AbstractEvent.Key(){...}

public GwtEvent.Key getKey(){
return KEY;
}
...
}
Wire up the handler's fire method

class HappyEvent extends GwtEvent {
static Key KEY = new Key(){
protected void fire(HappyHandler handler, HappyEvent event) {
handler.onHappiness(event);
};
...
}