Question

In my GWT project, I’m trying to get it so two DialogBoxes can pass information between each other. One of them holds a MapWidget, and when a button is pressed in the other DialogBox, the position information is received from that other DialogBox’s MapWidget. Does anyone have any tips for how I should coordinate between having two different DialogBoxes show up? Should I wrap the code for the two in a Composite? Furthermore, is there an example anywhere of dealing with two DialogBoxes at once in GWT? For example, if I click outside of the two boxes, both should be dismissed. I’m wondering if there’s a way to keep both of them in focus at once, so I can switch between the two without causing either to disappear.

Answer 1

Sharing Data Between Dialog Boxes

In my opinion, the “correct” way to do this would be to implement some sort of MVP structure in the application so that a presenter manages the view (DialogBoxes, among other things) and knows how to pass simple data to the view for it to display (the presenter would handle the MapWidget data, the view would take care of displaying it on the DOM).

However, if you’re looking for a quicker/more simpler approach, you have a couple of options (which you choose really depends on the application structure):

1. Create a Composite, as you mentioned, that knows how to pass the necessary data back and forth. By having the Composite manage the data object and tell the two DialogBoxes how to display it, you are actually approaching an MVP architecture within your Composite.
2. Subclass DialogBox into a class that contains a HandlerManager (sometimes used as an “Event Bus”) that fires events when the button is pressed. You can create events that are designed to pass data back and forth between the two DialogBoxes (even make them type-safe with type parameters). See this StackOverflow question for details on using a HandlerManager. The MVP article, linked above, also has some good information on using an event bus.

Model-View-Presenter is a tried-and-true method of structuring an application that results in more testable code, better project structure, and can help guide you when making decisions like this. I strongly recommend checking it out if you haven’t already.

Sharing Auto-Hide Functionality

GWT’s PopupPanel (on which DialogBox is based) offers a method addAutoHidePartner(Element) which is describe thusly:

Mouse events that occur within an autoHide partner will not hide a panel set to autoHide.

So, you can create two auto-hiding DialogBoxes that only close when you click outside both of them (e.g., they do not close when you click within either of the boxes) with the following code:

// Create the dialog boxes
DialogBox dbox1 = new DialogBox(true, false);
DialogBox dbox2 = new DialogBox(true, false);
// Set some visual options
dbox1.setPopupPosition(10, 10);
dbox2.setPopupPosition(200, 10);
dbox1.setAnimationEnabled(true);
dbox2.setAnimationEnabled(false);
// Set the dialog boxes' caption and content
dbox1.setHTML("Dialog Box 1");
dbox2.setHTML("Dialog Box 2");
dbox1.setWidget(new HTML("This is the first dialog box."));
dbox2.setWidget(new HTML("This is the second dialog box."));
// Making dobx2 a partner of dbox1 means clicking
// in dbox2 won't cause dbox1 to close
dbox1.addAutoHidePartner(dbox2.getElement());
// Similarly, setting dbox1 as a partner of dbox2 means
// clicking in dbox1 won't cause dbox2 to close
dbox2.addAutoHidePartner(dbox1.getElement());
// Show the dialog boxes
dbox1.show();
dbox2.show();

You can interact with either of the dialog boxes without the other closing. Omit the appropriate call to setAutoHidePartner if you only want a one-way partnership.