Add (hover) listener for grid cell after grid first attach

Question

I have something like this.

Grid<Stock> mygrid = new Grid<Stock>(store, cm)
{
    @Override
    protected void onAfterFirstAttach() 
    {       
        super.onAfterFirstAttach();
        //here do the binding for the cell elements that have myclass
    }
};

And for the view of mygrid I have this

view.setViewConfig(new GridViewConfig<Stock>()
{
    @Override
    public String getRowStyle(Stock model, int rowIndex)
    {
        return "";
    }

    @Override
    public String getColStyle(Stock model, ValueProvider<? super Stock, ?> valueProvider, int rowIndex, int colIndex)
    {       
        String style = "";
        if(SOME_CASE)
        {
            style = "myclass"; 
        }

        return style;
    }
});

What I want to do is onAfterFirstAttach I want to add some listener/handler that during hover will do something, let's say for the sake of simplicity, give an alert.

Is what I'm trying to do possible? Can I accomplish what I want without using JSNI or a library like gwtquery? Is it sure that onAfterFirstAttach all the cells that should have the class myclass will be available and accessible? If yes how can I attach the listener/handler that I want?

The questions seem a lot, but I believe they are all interconnected.

I'm using GWT 2.6 with GXT 3.1 on top of it.

Update

I forgot to mention that a feasible solution would be to add a listener for the mouse move on the whole grid, and then get each cell and check if it has the required class, but this seems such an overkill. There must be a simpler way.

Answer 1

A browser fires native events (click, focus, blur, etc.) regardless of whether you need them. These events "bubble up" the DOM tree giving you a chance to "listen" to them at the right level.

In your example you can create 30 listeners at the cell level, waiting for something to happen in "their" cell. This is a heavy (30 objects) and slow (it takes time to build and bind all of them) solution. Alternatively, you can create a single listener at the grid level, which listens to all events that bubble up from the cells and decides if something needs to be done or an event should be ignored. A single listener is lighter and can be created faster. On the flip side, it needs to examine events, although it's usually a fast and efficient operation (e.g. checking of an event source has a particular class name). Note also that this operation takes time when a browser typically does not have much to do anyway, so examining events only to ignore them does not impact user experience.

In my experience a single listener is almost always a better solution, although modern browsers and computers are so fast that the difference is rarely noticeable.