Java – custom valuechangehandler GWT

I need to write a custom valuechangehandler and call onvaluechange (valuechangeevent) But I don't understand how to write valuechangeevent

Maybe I understand the whole GWT event system is wrong Can I help you?

Editor: I asked how to create my own class for scheduling valuechangeevent I understand how to listen to it

The constructor of valuechangeevent is not visible and I cannot create it

Solution

If you want to fire valuechangeevent, you must implement the interface hasvaluechangehandlers through or class or somewhere in the class

A simple implementation is to use eventbus:

EventBus bus = new SimpleEventBus();

@Override
public void fireEvent(GwtEvent<?> event) {
    bus.fireEvent(event);
}

@Override
public HandlerRegistration addValueChangeHandler(ValueChangeHandler<T> handler) {
    return bus.addHandler(ValueChangeEvent.getType(),handler);
}

Note that you need to replace T with the type you want to trigger

Because you cannot create valuechangeevent, the direct scheduling event is completed through the fire method:

ValueChangeEvent.fire(this,value);

This refers to the class / field that implements hasvaluechangehandlers, value refers to the changed value, and you want to schedule the event