Java/JavaFX2: dynamic GUI, detect which button was pressed, extract id

Question

I'm a newbie in Java/JavaFX (I began yesterday evening). I'm building a dynamic GUI (crud) reading off a MySQL database.

I managed to display the data in a table and add a button next to each row.
Since the number of buttons is variable, I want to define only a common eventhandler.

The problem is that whenever I use event.getSource() (it's an ActionEvent) and display it, I get something like "Button[id=0, styleClass=button].

Question 1: Is there any way I could put the id in a variable? I can't get it out of the object.

As far as I know, I have to use the id, since I can't do something like this "if(event.getSource() == somebutton) {...}" since every generated button had the same variable name.

Now, this is the loop (inside a method called make_buttons) that builds the buttons. n_buttons is the number of buttons I want to build.

for(int counter = 0; counter < n_buttons; counter++){
        String newtext = new String("btn"+counter);
        Button btn = new Button();
        btn.setText(newtext);
        btn.setId(Integer.toString(counter));
        btn.setOnAction(myHandler);
        grid.add(btn,0,counter);
    }

Note that I'm placing the buttons on a gridpane one on top of the other.

Before that part I have my handler:

    final EventHandler<ActionEvent> myHandler = new EventHandler<ActionEvent>(){

    public void handle(final ActionEvent event) {
        Object new_output = event.getSource();
        System.out.println(new_output);
        event.consume();
        }
    };

Question 2: so, how can I differentiate which button fired the event in my particular case?

I know quite a few programming languages (Matlab, R, Python, C, Assembly, etc... but I'm a hobbyist), but it's the first time I'm working with GUI elements (except web languages and ActionScript 3). In actionscript I could just do something like event.getCurrentTarget and the use it exactly as if it were the object itself to read the id, properties, etc.

I looked everywhere and couldn't find anything (maybe my terminology was a bit approximative...).

assylias · Accepted Answer · 2012-09-03 12:52:19Z

6

If I understand your question correcty, you can simply access the clicked button in you handle method with the following code:

Object source = event.getSource();
if (source instanceof Button) { //should always be true in your example
    Button clickedBtn = (Button) source; // that's the button that was clicked
    System.out.println(clickedBtn.getId()); // prints the id of the button
}

answered Sep 3, 2012 at 12:52

assylias

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1 Comment

BlackRainbow Over a year ago

You got it!!! I tried to cast it too, but without the parentheses... Thank you very much.

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