更新JList时出现问题

Question

I'm having a poblem with my project, basically its a small app that stores synonyms. I have 2 JPanels populated with two JLists, one for the list of words and one with the correspondent synonyms. When you click on a word on one JList, the correspondent synonyms appears on the other JList then there are 2 JTextFields, for adding a word-synonym pair, in one field you insert the word in the other you insert the synonyms, split them creating an array with synonyms.split(" ") and store all in a Map this is the ListSelectionListener i have added to the word JList

    woordenList.addListSelectionListener(new ListSelectionListener() {

              public void valueChanged(ListSelectionEvent evt) {

                if (evt.getValueIsAdjusting()){

                  return;
                }

                getSynoniemen(evt);
             }
            });

And this is the method that gets the synonyms

    private void getSynoniemen(ListSelectionEvent e){

    if(e.getValueIsAdjusting()){


        return;

     }else{


         String woord=(String)woordenList.getSelectedValue();

         Object[] synArray=(Object[])beheer.getValues(woord);

         synoniemenList.setListData(synArray);

     }

}

If i add a word and synonyms into the lists when no item is selected it works fine, if i do this operation of adding items while instead, i have a word selected in the word-JList, the method getValues() with a null string is called, throwing an exception. i dont understand why, adding an element on the list also fires a list selection. Any advice?

Answer 1

我建议使用DefaultListModel来操作JList的内容。

Answer 2

i dont understand why, adding an element on the list also fires a list selection.

Somewhere in your code you must be changing the selected index.

Download and test the ListDemo example for How to Use Lists . When you run the code and "Hire" a person, then the list selection event fires (I added a System.out.println(...) to the listener). Then if you comment out:

//            list.setSelectedIndex(index);

the event is not fired. So you have a problem in your code. Compare your code to the working example code to see what if different.

If you need more help then post a SSCCE that demonstrates the problem.

Answer 3

This is a SSCCE of my project, i've left out all exceptions and comments and non relevant buttons, labels, methods. Try to insert a word with its synonyms, and then select a word, then while the word is selected try to insert another pair word-synonyms, there will come the exception
import javax.swing.AbstractListModel; import javax.swing.DefaultListModel; import javax.swing.JList; import javax.swing.JPanel; import javax.swing.JFrame; import javax.swing.JScrollPane; import java.awt.Rectangle; import java.util.HashMap; import java.util.Map; import java.util.Set; import javax.swing.JTextField; import javax.swing.JButton; import javax.swing.event.ListSelectionEvent; import javax.swing.event.ListSelectionListener;

public class Synonims extends JFrame {

private static final long serialVersionUID = 1L;
private JPanel jContentPane = null;
private JScrollPane wordsPane = null;
private JScrollPane synosymsPane = null;
private JTextField wordField = null;
private JTextField synonymsField = null;
private JButton addButton = null;
private JList wordsList=new JList(new DefaultListModel());
private JList synonymsList=new JList(new DefaultListModel());
private SynonymsManager manager=new SynonymsManager();

//default const
public Synonims() {
    super();
    initialize();
}
//init
private void initialize() {
    this.setSize(413, 285);
    this.setDefaultCloseOperation(JFrame.EXIT_ON_CLOSE);
    this.setContentPane(getJContentPane());
    this.setTitle("JFrame");
}

//contentpane
private JPanel getJContentPane() {
    if (jContentPane == null) {
        jContentPane = new JPanel();
        jContentPane.setLayout(null);
        jContentPane.add(getWordsPane(), null);
        jContentPane.add(getSynosymsPane(), null);
        jContentPane.add(getWordField(), null);
        jContentPane.add(getSynonymsField(), null);
        jContentPane.add(getAddButton(), null);
    }
    return jContentPane;
}
//RELEVANT: LISTSELECTIONLISTENER
private JScrollPane getWordsPane() {
    if (wordsPane == null) {
        wordsPane = new JScrollPane();
        wordsPane.setBounds(new Rectangle(16, 15, 121, 177));
        wordsPane.getViewport().add(wordsList,null);
        wordsList.addListSelectionListener(new ListSelectionListener() {

              public void valueChanged(ListSelectionEvent evt) {


                getSyn(evt);
             }
            });
    }
    return wordsPane;
}
//RELEVANT: GET THE SYNONYMS OF THE SELECTED WORD
public void getSyn(ListSelectionEvent e){
    String word=(String)wordsList.getSelectedValue();
    Object[] synArray=(Object[])manager.getValues(word);
    synonymsList.setListData(synArray);
}

//synonymspane
private JScrollPane getSynosymsPane() {
    if (synosymsPane == null) {
        synosymsPane = new JScrollPane();
        synosymsPane.setBounds(new Rectangle(254, 14, 133, 181));
        synosymsPane.getViewport().add(synonymsList,null);
    }
    return synosymsPane;
}

//wordfield
private JTextField getWordField() {
    if (wordField == null) {
        wordField = new JTextField();
        wordField.setBounds(new Rectangle(16, 209, 129, 27));
    }
    return wordField;
}

//synonymsfield
private JTextField getSynonymsField() {
    if (synonymsField == null) {
        synonymsField = new JTextField();
        synonymsField.setBounds(new Rectangle(254, 207, 136, 30));
    }
    return synonymsField;
}

//the button
private JButton getAddButton() {
    if (addButton == null) {
        addButton = new JButton();
        addButton.setBounds(new Rectangle(164, 228, 72, 25));
        addButton.setText("save");
        addButton.addActionListener(new java.awt.event.ActionListener() {
            public void actionPerformed(java.awt.event.ActionEvent e) {
                addAction(); 
            }
        });
    }
    return addButton;
}
//RELEVANT: THE METHODS THAT LOADS BOTH WORD AND SYNONYMS
public void addAction(){
String newWord=wordField.getText();
String newSynonyms= synonymsField.getText();
String[] synonymsArray=newSynonyms.split(" ");
manager.addSyn(newWord, synonymsArray);
wordField.setText("");
synonymsField.setText("");
wordsList.setListData(manager.getKeys());
}

//INNER CLASS FOR THE SYNONYMS
public class Synonym{

    private String[] synonym=null;

    public Synonym(String[]synonym){
        this.synonym=synonym;
    }

    public String[] getSynonyms(){
        return this.synonym;
    }
}

//INNER CLASS THAT MANAGES THE SYNONYMS
public class SynonymsManager extends AbstractListModel{
    private Map<String,Synonym> manager=null;

    public SynonymsManager(){
        manager=new HashMap<String,Synonym>();
    }

    public void addSyn(String woord, String[] synonyms){
       Synonym syn=new Synonym(synonyms);
         manager.put(woord, syn);
         fireContentsChanged(this,0,getSize() -1);
    }

    public Object getElementAt(int arg0) {
        return null;
    }
    public int getSize() {
        return 0;
    }

    public Object[] getKeys(){

        Set<String>keySet=manager.keySet();
        Object[] keys=keySet.toArray();
        return keys;
    }
    public Object[] getValues(String woord){

        Object[] values=search(woord).getSynonyms();

        return values;
    }
     public Synonym search(String word){

         return manager.get(word);
     }
}

public static void main(String[] args){

    Synonims s=new Synonims();
    s.setVisible(true);

}

}