GWT: Drag&Drop Event for TextField?

Question

I wonder how it is possible to listen for the drop event for a TextField . I need to intercept that events in order to do value checks.

I wrote an extended TextBox , which fires TextChangeEvents . But when i drop a text into the text field, I don't get a call for the onBrowserEvent(Event event) method.

Any hint?

public class ExtendedTextBox extends TextBox {

    /**
     * Creates an empty extended text box.
     */
    public ExtendedTextBox() {
        super();

        // Catch the browser events.
        sinkEvents(Event.ONKEYUP);
        sinkEvents(Event.ONPASTE);

    }

    @Override
    public void onBrowserEvent(Event event) {
        super.onBrowserEvent(event);
        System.out.println(event.getTypeInt());

        switch (event.getTypeInt()) {
            case Event.ONKEYUP:
            case Event.ONPASTE: {
            // Fire the event after the text box shows the new data.
            Scheduler.get().scheduleDeferred(new ScheduledCommand() {

                @Override
                public void execute() {
                    fireEvent(new TextChangeEvent(ExtendedTextBox.this.getText()));
                }
            });
            break;
        }
        default:
        }
    }

    /**
     * Add a given {@link TextChangeEventHandler} to the widget.
     * 
     * @param handler
     *            the handler
     * @return {@link HandlerRegistration} used to remove the handler
     */
    public HandlerRegistration addTextChangeEventHandler(TextChangeEventHandler handler) {
        return addHandler(handler, TextChangeEvent.TYPE);
    }
}

Answer 1

A TextBox should fire a ChangeEvent (or ValueChangeEvent - don't know at the moment). So you could easily do something like this inside your constructor:

this.addChangeHandler(new ChangeHandler ...

If that's not enough, you could also listen to the Focus event.

Answer 2

Thanks for your help. I figured it out by myself today and it is quiet simple. I didn't notice, that there is already the DropHandler .

You can do this for example in the constructor:

addDropHandler(new DropHandler() {

    @Override
    public void onDrop(DropEvent event) {
        if(!event.getDataTransfer().getData("text/plain").isEmpty()) {
            Scheduler.get().scheduleDeferred(new ScheduledCommand() {

                @Override
                public void execute() {
                    fireEvent(new TextChangeEvent(ExtendedTextBox.this.getText()));
                }
            });
        }

    }
});

To prevent the default behaviour of the TextField just add event.preventDefault(); . Now you can get the input by calling event.getDataTransfer().getData("text/plain") and do your input validation etc.

And as side effect the onBrowserEvent(Event event) method is called now by dropping something into the text field. But the type int is -1 , so it's not really helpful at this place.