JList og sortering

Jeg synes det virker lidt tørt at smide det over i et array først, sortere det, og smide det tilbage til listen hver gang jeg tilføjer et nyt element. Så det er derfor jeg gerne vil høre om der er andre mere hensigtsmæssige løsninger, denne beskrevne løsning kunne godt gå hen og blive lidt irriterende med mange elementer.

Jeg tror den generelle metode er at sortere elementerne inden du propper dem ind i listen. Det er jo blot en visning af en ArrayList eller en Vector, så det er jo essentielt den bagvedliggende datastruktur du skal sortere.

Kig her ellers:
http://java.sun.com/docs/books/tutorial/uiswing/components/list.html

Denne liste sorterer indholdet alfabetisk. Også når du tilføjer nye elementer.


import javax.swing.*;
import java.util.*;

public class SortedListModel extends AbstractListModel {

  SortedSet model;

  public SortedListModel() {
    model = new TreeSet();
  }

  public int getSize() {
    return model.size();
  }

  public Object getElementAt(int index) {
    return model.toArray()[index];
  }

  public void add(Object element) {
    if (model.add(element)) {
      fireContentsChanged(this, 0, getSize());
    }
  }

  public void addAll(Object elements[]) {
    Collection c = Arrays.asList(elements);
    model.addAll(c);
    fireContentsChanged(this, 0, getSize());
  }

  public void clear() {
    model.clear();
    fireContentsChanged(this, 0, getSize());
  }

  public boolean contains(Object element) {
    return model.contains(element);
  }

  public Object firstElement() {
    return model.first();
  }

  public Iterator iterator() {
    return model.iterator();
  }

  public Object lastElement() {
    return model.last();
  }

  public boolean removeElement(Object element) {
    boolean removed = model.remove(element);
    if (removed) {
      fireContentsChanged(this, 0, getSize());
    }
    return removed; 
  }
}

du kan teste "sortedListModel" vha. af denne klasse:


import java.awt.*;
import java.awt.event.*;
import javax.swing.*;
import java.util.Iterator;

public class DualListBox extends JPanel {

  private static final Insets EMPTY_INSETS = new Insets(0,0,0,0);
  private static final String ADD_BUTTON_LABEL = "Add >>";
  private static final String REMOVE_BUTTON_LABEL = "<< Remove";
  private static final String DEFAULT_SOURCE_CHOICE_LABEL = "Available Choices";
  private static final String DEFAULT_DEST_CHOICE_LABEL = "Your Choices";
  private JLabel sourceLabel;
  private JList sourceList;
  private SortedListModel sourceListModel;
  private JList destList;
  private SortedListModel destListModel;
  private JLabel destLabel;
  private JButton addButton;
  private JButton removeButton;
  public DualListBox() {
    initScreen();
  }
  public String getSourceChoicesTitle() {
    return sourceLabel.getText();
  }
  public void setSourceChoicesTitle(String newValue) {
    sourceLabel.setText(newValue);
  }
  public String getDestinationChoicesTitle() {
    return destLabel.getText();
  }
  public void setDestinationChoicesTitle(String newValue) {
    destLabel.setText(newValue);
  }
  public void clearSourceListModel() {
    sourceListModel.clear();
  }
  public void clearDestinationListModel() {
    destListModel.clear();
  }
  public void addSourceElements(ListModel newValue) {
    fillListModel(sourceListModel, newValue);
  }
  public void setSourceElements(ListModel newValue) {
    clearSourceListModel();
    addSourceElements(newValue);
  }
  public void addDestinationElements(ListModel newValue) {
    fillListModel(destListModel, newValue);
  }
  private void fillListModel(SortedListModel model, ListModel newValues) {
    int size = newValues.getSize();
    for (int i=0; i<size; i++) {
      model.add(newValues.getElementAt(i));
    }
  }
  public void addSourceElements(Object newValue[]) {
    fillListModel(sourceListModel, newValue);
  }
  public void setSourceElements(Object newValue[]) {
    clearSourceListModel();
    addSourceElements(newValue);
  }
  public void addDestinationElements(Object newValue[]) {
    fillListModel(destListModel, newValue);
  }
  private void fillListModel(SortedListModel model, Object newValues[]) {
    model.addAll(newValues);
  }
  public Iterator sourceIterator() {
    return sourceListModel.iterator();
  }
  public Iterator destinationIterator() {
    return destListModel.iterator();
  }
  public void setSourceCellRenderer(ListCellRenderer newValue) {
    sourceList.setCellRenderer(newValue);
  }
  public ListCellRenderer getSourceCellRenderer() {
    return sourceList.getCellRenderer();
  }
  public void setDestinationCellRenderer(ListCellRenderer newValue) {
    destList.setCellRenderer(newValue);
  }
  public ListCellRenderer getDestinationCellRenderer() {
    return destList.getCellRenderer();
  }
  public void setVisibleRowCount(int newValue) {
    sourceList.setVisibleRowCount(newValue);
    destList.setVisibleRowCount(newValue);
  }
  public int getVisibleRowCount() {
    return sourceList.getVisibleRowCount();
  }
  public void setSelectionBackground(Color newValue) {
    sourceList.setSelectionBackground(newValue);
    destList.setSelectionBackground(newValue);
  }
  public Color getSelectionBackground() {
    return sourceList.getSelectionBackground();
  }
  public void setSelectionForeground(Color newValue) {
    sourceList.setSelectionForeground(newValue);
    destList.setSelectionForeground(newValue);
  }
  public Color getSelectionForeground() {
    return sourceList.getSelectionForeground();
  }
  private void clearSourceSelected() {
    Object selected[] = sourceList.getSelectedValues();
    for (int i=selected.length-1; i >= 0; --i) {
      sourceListModel.removeElement(selected[i]);
    }
    sourceList.getSelectionModel().clearSelection();
  }
  private void clearDestinationSelected() {
    Object selected[] = destList.getSelectedValues();
    for (int i=selected.length-1; i >= 0; --i) {
      destListModel.removeElement(selected[i]);
    }
    destList.getSelectionModel().clearSelection();
  }
  private void initScreen() {
    setBorder(BorderFactory.createEtchedBorder());
    setLayout(new GridBagLayout());
    sourceLabel = new JLabel(DEFAULT_SOURCE_CHOICE_LABEL);
    sourceListModel = new SortedListModel();
    sourceList = new JList(sourceListModel);
    add(sourceLabel, new GridBagConstraints(0, 0, 1, 1, 0, 0, GridBagConstraints.CENTER, GridBagConstraints.NONE, EMPTY_INSETS, 0, 0));
    add(new JScrollPane(sourceList), new GridBagConstraints(0, 1, 1, 5, .5, 1, GridBagConstraints.CENTER, GridBagConstraints.BOTH, EMPTY_INSETS, 0, 0));

    addButton = new JButton(ADD_BUTTON_LABEL);
    add(addButton, new GridBagConstraints(1, 2, 1, 2, 0, .25, GridBagConstraints.CENTER, GridBagConstraints.NONE, EMPTY_INSETS, 0, 0));
    addButton.addActionListener(new AddListener());
    removeButton = new JButton(REMOVE_BUTTON_LABEL);
    add(removeButton, new GridBagConstraints(1, 4, 1, 2, 0, .25, GridBagConstraints.CENTER, GridBagConstraints.NONE, new Insets(0,5,0,5), 0, 0));
    removeButton.addActionListener(new RemoveListener());

    destLabel = new JLabel(DEFAULT_DEST_CHOICE_LABEL);
    destListModel = new SortedListModel();
    destList = new JList(destListModel);
    add(destLabel, new GridBagConstraints(2, 0, 1, 1, 0, 0, GridBagConstraints.CENTER, GridBagConstraints.NONE, EMPTY_INSETS, 0, 0));
    add(new JScrollPane(destList), new GridBagConstraints(2, 1, 1, 5, .5, 1.0, GridBagConstraints.CENTER, GridBagConstraints.BOTH, EMPTY_INSETS, 0, 0));
  }

  public static void main(String args[]) {
    JFrame f = new JFrame("Dual List Box Tester");
    DualListBox dual = new DualListBox();
    dual.addSourceElements(new String[] {"One", "Two", "Three"});
    dual.addSourceElements(new String[] {"Four", "Five", "Six"});
    dual.addSourceElements(new String[] {"Seven", "Eight", "Nine"});
    dual.addSourceElements(new String[] {"Ten", "Eleven", "Twelve"});
    dual.addSourceElements(new String[] {"Thirteen", "Fourteen", "Fifteen"});
    dual.addSourceElements(new String[] {"Sixteen", "Seventeen", "Eighteen"});
    dual.addSourceElements(new String[] {"Nineteen", "Twenty", "Thirty"});
    f.getContentPane().add(dual, BorderLayout.CENTER);
    f.setSize(400, 300);
    f.setVisible(true);
  }
  private class AddListener implements ActionListener {
    public void actionPerformed(ActionEvent e) {
      Object selected[] = sourceList.getSelectedValues();
      addDestinationElements(selected);
      clearSourceSelected();
    }
  }
  private class RemoveListener implements ActionListener {
    public void actionPerformed(ActionEvent e) {
      Object selected[] = destList.getSelectedValues();
      addSourceElements(selected);
      clearDestinationSelected();
    }
  }
}

men hvor i SortedListModel ligger sorteringen, kan ikke umiddelbart overskue det, ville måske hellere extende defaultlistmodel med nogle sorteringsmetoder da jeg allerede har brugt defaultlistmodel's metoder og typer ret mange steder i mit program.

det sker her:

  SortedSet model;

  public SortedListModel() {
    model = new TreeSet();
  }


Hvis du kigger i API'en, så er TreeSet beskrevet:
/**
    * Constructs a new, empty set, sorted according to the elements' natural
    * order.  All elements inserted into the set must implement the
    * <tt>Comparable</tt> interface.  Furthermore, all such elements must be
    * <i>mutually comparable</i>: <tt>e1.compareTo(e2)</tt> must not throw a
    * <tt>ClassCastException</tt> for any elements <tt>e1</tt> and
    * <tt>e2</tt> in the set.  If the user attempts to add an element to the
    * set that violates this constraint (for example, the user attempts to
    * add a string element to a set whose elements are integers), the
    * <tt>add(Object)</tt> call will throw a <tt>ClassCastException</tt>.
    *
    * @see Comparable
    */

ser lige om jeg kan finde ud af at tilføje den funktionalitet til defaultlistmodel og vender tilbage