• 0

Button Event Handler in a JList, Please help.


Question

Hi everyone,

I have created a small Java application which has a JList. The JList uses a custom cell renderer I named SmartCellRenderer. The SmartCellRenderer extends JPanel and implements the ListCellRenderer. I have added two buttons on the right side inside the JPanel of the SmartCellRenderer, since I want to buttons for each list item, and I have added mouse/action listeners for both buttons. However, they don't respond. It seems that the JList property overcomes the buttons underneath it. So the buttons never really get clicked because before that happens the JList item is being selected beforehand. I've tried everything. I've put listeners in the Main class, called Editor, which has the JList and also have listeners in the SmartCellRenderer itself and none of them get invoked.

I also tried a manual solution. Every time the event handler for the JList was invoked (this is the handler for the JList itself and not the buttons), I sent the mouse event object to the SmartCellRenderer to manually check if the point the click happened was on one of the buttons in order to handle it.

I used:

// Inside SmartCellRenderer.java

// e is the mouse event object being passed from the Editor whenever

// a JList item is selected or clicked on

Component comp = this.getComponent (e.getX(), e.getY())

if(!(comp instanceof JButton)) {

System.out.println("Recoqnizedt, but not a button click...");

//return;

} else {

System.out.println("Recognizedt, IT IS A MOUSE CLICK, PROCESSING...");

}

System.out.println("VALUEomp.toString());

What I realized is that not only this still doesn't work (it never realizes the component as a JButton) it also throws an exception for the last line saying comp is null. Meaning with the passed x,y position the getComponent() returns a null which happens when the coordinates passed to it are outside the range of the Panel. Which is a whole other problem?

I have yet to find an example on the web, using Google, that demonstrated using buttons inside a JList.

Can anyone help me with this. Thanks.

3 answers to this question

Recommended Posts

  • 0

might help if you post your code....

what you have to do is

create a button, assign the button a listener and then assign to the jlist.

I have no jdk at the moment, but here is some code

class MyList extends JList implements ActionListener
{

    JButton b1 = new JButton();
    JButton b2 = new JButton();

    public MyList()
   {
       super(); 
      b1.addActionListener(this);
      b2.addActionListener(this);
      this.add(b1);
      this.add(b2);
   }

   public actionPerformed(ActionEvent e)
  { 
     System.out.println(e.toString());
   }
}

  • 0

I know the above code isnt what you are looking for, but your key problem is that you have not hooked your buttons into a listener. ie. addActionListener(this).

this is why you never here calls from the button being pressed, because nothing registered to listening for the event

This topic is now closed to further replies.
  • Recently Browsing   0 members

    • No registered users viewing this page.
  • Posts

    • 99% of Control Panel will be moved to Settings. Then by 2050, 20% of settings will have been moved to the Configuration Menu. I have no issues with Settings as it exists now in Windows 11. Bring everything over and be done with it.
    • We collect the few carcasses we get (as long as drivers report them, as they should) and while we have our fair share, we don't have nearly enough crashes with deer "to paint the roads with deer carcasses" in Finland. Also, if you can't handle the risks, DO NOT DRIVE. I really don't want everything to be so simple and stupid, that I don't have to worry about my surroundings (I also hate Apple devices because they kind of decide everything for you and offer very little customization vs. Android). Most people probably encounter much higher risks and dangers in their daily jobs than they encounter on roads. Just a few weeks ago I twisted my anckle at work while walking and I haven't had even a near miss with an animal in traffic for many years despite driving something like 27000+ km/year (there were a couple of off years in there too) and seeing many deer, a few moose and many smaller creatures on the road. I find it extremely rare to have deer stumble directly in front of me - it happens, but in my opinion not nearly enough to warrant considering it super dangerous (I actually find it exhilarating when it does happen as it changes the daily commute and it actually requires me to stay focused). It is probably more common to have some idiot with their face glued to their phone wonder in front of you or a kid on an electric scooter disregard all traffic rules. Here in the Nordics we also have plenty of snow and that kind of f's up anything that relies on lines or other clear lane indicators. The one time I have (kind of) started raging while driving was when I had a loan car from service and it had lane guidance. That freaking thing basically felt like it wanted to hit every pothole and bump it could and I really, really freaking hated it (came close to ripping the whole steering wheel of, I tell you . Didn't feel safer at all, quite the contrary, and it distracted me from the road more than anything else I've driven before, constantly fighting that f'ing thing to go where I wanted it to go (no clear lines, a crack in the pavement, etc. and it became confused as hell and required more adjusting than any traditional car). Also noteworthy that globally the amount of people with driver's licenses is pretty low (like under 20 %), many countries have great public transport systems and many walk and cycle (even during the winter).
    • The snipping tool has come a long way. Every feature they add reduces the need for third-party utilities; in the past it seemed MS shied away from adding features to some in-box tools just so there would be a more robust third-party developer base. Now that we finally have boxes, circles and arrows, can they finally add text bubbles?
    • It's a custom built linear internal power supply which is isolated from the mainboard, it is very clean. External switching PSUs can be noisy and send that noise to the components. Linear external power supplies are expensive for good ones and are rare to see included with a device hence why they are sold optionally.
  • Recent Achievements

    • Week One Done
      BlakeBringer earned a badge
      Week One Done
    • Week One Done
      Helen Shafer earned a badge
      Week One Done
    • First Post
      emptyother earned a badge
      First Post
    • Week One Done
      Crunchy6 earned a badge
      Week One Done
    • One Month Later
      KynanSEIT earned a badge
      One Month Later
  • Popular Contributors

    1. 1
      +primortal
      660
    2. 2
      ATLien_0
      266
    3. 3
      Michael Scrip
      235
    4. 4
      Steven P.
      164
    5. 5
      +FloatingFatMan
      153
  • Tell a friend

    Love Neowin? Tell a friend!