my jComboBox does not react to my keyListener and actionPerform performs weired stuff

I am trying to search for UserName and return values onto jComboBox, here is the code

public void actionPerformed(java.awt.event.ActionEvent e) {
    sr = new Search(((String) jComboBoxReceiver.getSelectedItem()));    
    usrList = sr.searchUser();
    String[] userList = new String[usrList.size()] ;
    for(int i=0;i<usrList.size();i++){
        userList[i]= usrList.get(i).getUserName();
    }
    model = new DefaultComboBoxModel(userList);
    jComboBoxReceiver.setModel(model);
}

after you click to somewhere else or click enter,it will conduct the search, however, it will go search for the first item again, which is very confusing... then i tried using key Pressed

if(e.getKeyCode()==13){
    sr = new Search(((String) jComboBoxReceiver.getSelectedItem()));    
    usrList = sr.searchUser();
    String[] userList = new String[usrList.size()] ;
    for(int i=0;i<usrList.size();i++){
        userList[i]= usrList.get(i).getUserName();
    }
    model = new DefaultComboBoxModel(userList);
    jComboBoxReceiver.setModel(model);
}

And this one does not react at all.

Wow, you're rebuilding a ComboBoxModel each time ? Isn't it a little expensive ? You know there is a MutableComboBoxModel, also implemented by DefaultComboBoxModel that would allow you to add/remove elements from you combobox without rebuilding its model each time ?

Concerning your question, I don't understand the statement

However, if i do that, it does perform correctly, however, it will go search for the first item again

Do you mean your JComboBox starts to blink with content being modified each time ?

if so, maybe is it because your ActionListener is linked to JComboBox, which content changes continuously.

Anyway, i suggest you add some logs, like

sr = new Search(((String) jComboBoxReceiver.getSelectedItem()));    
DefaultComboBoxModel model = (DefaultComboBoxModel) jComboBoxReceiver.getModel();
model.remvoeAllElements();
usrList = sr.searchUser();
String[] userList = new String[usrList.size()] ;
for(int i=0;i<usrList.size();i++){
    String username = usrList.get(i).getUserName();
    System.out.println(username); // feel free to instead use one loger
    model.addElement(username);
}

Besides, i would tend to suggest you an other approach, in which combo box model don't contain simple Strings, but rather User objects, with a ListCellRenderer displaying only the user name.