如何使用DefaultListModel（）添加或删除元素时更新JList

Question

i know this question asked many times before. However, i spent on hours to research about a way to update a JList, and i couldn't handle with this issue. I'm trying to implement a JList which shows who is online or offline.(It holds JLabels i guess this is the only way for holding a string with an icon). I have my own CellRenderer() which is like;

public class UserRenderer extends DefaultListCellRenderer {


    @Override
    public Component getListCellRendererComponent(JList list, Object value,int index, boolean isSelected, boolean hasFocus) {

       if(value instanceof ClientObject){

           final ClientObject clientObject = (ClientObject) value;
           JLabel label = (JLabel) super.getListCellRendererComponent(list, clientObject.getNickName(), index, isSelected, hasFocus);

           if(clientObject.isIsOnline()){

               label.setIcon(iconArray[1]);
           }
           else{

               label.setIcon(iconArray[0]);
           }

           return label;
       }

       else {

           return super.getListCellRendererComponent(list, value, index, isSelected, hasFocus);
       }
    }

}

Moreover, i construct client's list whenever he/she gets connected to server with this way;

private void buildBuddyList(ClientObject tempClientObject){

    if( tempClientObject.getBuddyList().size() > 0 ){

        mainClient.setBuddyList(tempClientObject.getBuddyList());

        for (Iterator<ClientObject> iter = mainClient.getBuddyList().iterator(); iter.hasNext();) {

            ClientObject tempon = iter.next();

                if(tempon.isIsOnline()){

                    model.addElement(tempon);
                    labelIconList.put(tempon, iconArray[1]);
                }

                else{

                    model.addElement(tempon);
                    labelIconList.put(tempon, iconArray[0]);
                }
        }
    }
}

The trick which i use when a client changed his/her status (becomes online/offline) is i get rid off all elements with model.clear() and start to construct the list again. Here is the code segment;

       if(tempClientObject.isStatusChanged()){

          if(tempClientObject.isIsConnected()){ 

                System.out.println(tempClientObject.getUserName() + " is ONLINE");

                model.clear();

                for (Iterator<Map.Entry<ClientObject,ImageIcon>> iter = labelIconList.entrySet().iterator(); iter.hasNext();) {

                    Map.Entry<ClientObject,ImageIcon> pairs = iter.next();

                    ClientObject changedOnlineStatusClient = (ClientObject) pairs.getKey();

                    if(changedOnlineStatusClient.getUserName().equals(tempClientObject.getUserName())){

                        changedOnlineStatusClient.setIsOnline(tempClientObject.isIsOnline());
                    }

                    model.addElement(changedOnlineStatusClient);
                }
          }

          else{

                System.out.println(tempClientObject.getUserName() + " is OFFLINE");                

                model.clear();

                for (Iterator<Map.Entry<ClientObject,ImageIcon>> iter = labelIconList.entrySet().iterator(); iter.hasNext();) {
                    Map.Entry<ClientObject,ImageIcon> pairs = iter.next();
                    ClientObject changedOnlineStatusClient = (ClientObject) pairs.getKey();

                    if(changedOnlineStatusClient.getUserName().equalsIgnoreCase(tempClientObject.getUserName())){

                        changedOnlineStatusClient.setIsOnline(tempClientObject.isIsOnline());
                    }

                    model.addElement(changedOnlineStatusClient);
                }                      
          }
       }

I can assure that logical system works fine.(I can check the actions if they are working properly on background). Only the problem is sometimes when a client connected to server JList looks blank even though it adds elements into model. i will appreciate for every answer. And thanks anyway

Answer 1

only comment, not an answer

there no require for one dimensional JList

if(value instanceof ClientObject){

because Object from

getListCellRendererComponent(JList list, Object value, int index, 
       boolean isSelected, boolean hasFocus) {

returns the same value, then to test this value if == or equeals ...

Answer 2

First of all thanks for all your replies. On the other hand, i corrected my issue with creating a new model whenever it has to be get updated. So the code segment is like this;

DefaultListModel tempModel = new DefaultListModel();

// add or remove elements from tempModel

buddyList.setModel( tempModel );

i'm not sure about if it is the only correct way but at least it works.

Answer 3

Call model.fireContentsChanged() method.

JavaDoc on AbstractListModel