Need flexible Java key/value collection class for JComboBox
I have a model class that stores keys and values:
public class KeyValue {
private Object key;
private String value;
KeyValue () {
}
KeyValue (Object key, String value) {
this.key=key;
this.value=value;
}
public Object getKey() {
return this.key;
}
public void setKey(Object key) {
this.key=key;
}
public String getValue() {
return this.value;
}
public void setV开发者_开发知识库alue(String value) {
this.value=value;
}
@Override
public String toString() {
return this.value;
}
}
I use this class to populate a JComboBox
's Model:
for (int i = 0; i < universes.length; i++) {
ComboBox_Universes.addItem(new KeyValue(infoObject.ID,infoObject.title));
}
I would like to refactor this logic to use a Java collection class (call it KeyValueCollection
) that can support two objectives:
1) the KeyValueCollection
can be used to populate the JComboBox
's Model. Something like:
//get a KeyValueCollection filled with data from helper class
KeyValueCollection universeCollection = Repository.getUniverseCollection();
//use this collection as the JComboBox's model
ComboBox_Universes.setModel(universeCollection);
2) I can use the KeyValueCollection
to convert a key to a value:
//ID retrieve from another control
int universeID = (int)this.Table_Values.getModel().getValueAt(row, COLUMN_ID);
//convert ID to name
String universeName = universeCollection.get(universeID).getValue();
In the .NET world, I would use the KeyedCollection class for this, but I'm not very familiar with Java.
Help is greatly appreciated.
You can use a custom class like this one (run main function to see its behavior) :
import java.awt.BorderLayout;
import java.awt.Component;
import java.awt.event.ActionEvent;
import java.awt.event.ActionListener;
import java.util.ArrayList;
import java.util.Collection;
import java.util.HashMap;
import java.util.List;
import java.util.Map;
import java.util.Set;
import java.util.TreeMap;
import javax.swing.AbstractListModel;
import javax.swing.ComboBoxModel;
import javax.swing.DefaultListCellRenderer;
import javax.swing.JComboBox;
import javax.swing.JFrame;
import javax.swing.JLabel;
import javax.swing.JList;
import javax.swing.JPanel;
public class KeyValueComboboxModel extends AbstractListModel implements ComboBoxModel, Map<String, String> {
private TreeMap<String,String> values = new TreeMap<String,String>();
private Map.Entry<String, String> selectedItem = null;
public Object getSelectedItem() {
return selectedItem;
}
public void setSelectedItem(Object anItem) {
this.selectedItem = (java.util.Map.Entry<String, String>) anItem;
fireContentsChanged(this, -1, -1);
}
public Object getElementAt(int index) {
List<Map.Entry<String, String>> list = new ArrayList<Map.Entry<String, String>>(values.entrySet());
return list.get(index);
}
public int getSize() {
return values.size();
}
public void clear() {
values.clear();
}
public boolean containsKey(Object key) {
return values.containsKey(key);
}
public boolean containsValue(Object value) {
return values.containsValue(value);
}
public Set<java.util.Map.Entry<String, String>> entrySet() {
return values.entrySet();
}
public String get(Object key) {
return values.get(key);
}
public Set<String> keySet() {
return values.keySet();
}
public String put(String key, String value) {
return values.put(key, value);
}
public String remove(Object key) {
return values.remove(key);
}
public int size() {
return values.size();
}
public Collection<String> values() {
return values.values();
}
public boolean isEmpty() {
return values.isEmpty();
}
public void putAll(Map<? extends String, ? extends String> m) {
values.putAll(m);
}
private static String entryToString(Map.Entry<String, String> entry) {
String str = "" + entry.getKey() + "->" + entry.getValue();
return str;
}
public static void main(String[] args) {
Map<String,String> map= new HashMap<String,String>(){{
put("1","blue");
put("2","red");
put("3","white");
put("4","black");
}};
JFrame f = new JFrame();
f.setContentPane(new JPanel(new BorderLayout()));
KeyValueComboboxModel model = new KeyValueComboboxModel();
model.putAll(map);
final JComboBox combo = new JComboBox(model);
combo.setRenderer(new DefaultListCellRenderer(){
@Override
public Component getListCellRendererComponent(JList list, Object value, int index,
boolean isSelected, boolean cellHasFocus) {
if(value instanceof Map.Entry){
Map.Entry<String,String> entry = (java.util.Map.Entry<String, String>) value;
String str = entryToString(entry);
return super.getListCellRendererComponent(list, str, index, isSelected, cellHasFocus);
}
return super.getListCellRendererComponent(list, value, index, isSelected, cellHasFocus);
}
});
final JLabel lab = new JLabel("Nothing selected");
combo.addActionListener(new ActionListener(){
public void actionPerformed(ActionEvent e) {
if(combo.getSelectedItem()!=null){
lab.setText(entryToString((java.util.Map.Entry<String, String>) combo.getSelectedItem()));
} else {
lab.setText("");
}
}
});
f.getContentPane().add(combo,BorderLayout.CENTER);
f.getContentPane().add(lab,BorderLayout.SOUTH);
f.setSize(300,80);
f.setDefaultCloseOperation(JFrame.EXIT_ON_CLOSE);
f.setLocationRelativeTo(null);
f.setVisible(true);
}
}
EDIT : to handle the selected item and keys, you may add these methods:
public void setSelectedKey(String key){
selectedItem = values.ceilingEntry(key);
setSelectedItem(key);
}
public void setSelectedItem(String key, String value){
values.put(key, value);
setSelectedKey(key);
}
By default, values are ordered following the natural order of the keys (alphabetical order of the keys, here, because these are String
). If you need an other ordering, add a java.util.Comparator
to the TreeMap
(see TreeMap documentation).
The Map (implementation HashMap) is a Key-Value class.
It converts from key to value using the method #get.
There are also method to access all keys, all values and so on. So you should have no problem to fill a model with it.
It also contains a Key-Value pair that is called Map.Entry.
Your second requirement suggests that you want a Map, but ComboboxModel is a ListModel, which suggests that you'll want to be able to efficiently retrieve elements by "index".
I don't believe any of the standard collections can do this for you as simply as you'd like. You can either create a Map, and then copy the values to a separate List/ComboboxModel, or you could use something like IndexedList (a List implementation that maintains an index Map).
What about java.util.Map
implementations?
with HashMap
, for example, you can have:
Map<Object, String> map = new HashMap<Object, String>();
map.put(key, value);
Object value = map.get(key);
However, you can't directly populate the JComboBox
with the Map
. You can add all keys to the JComboBox
, and then get the corresponding values when needed. Adding can be done in many ways, two of which:
new JComboBox(map.keySet().toArray(new Object[]));
by a loop:
for (Object key : map.keySet() { comboBox.addItem(key); }
I think that a plain HashMap<Object,String>
can address most of your needs:
// Build the map
Map<Object,String> map = new HashMap<Object,String>();
for(InfoObject io : universes)
map.put(io.ID,io.title);
// Populate the ComboBox
for(String s : map.values())
ComboBox_Universes.addItem(s);
// Convert ID to name
int universeID = (int)this.Table_Values.getModel().getValueAt(row, COLUMN_ID);
String universeName = map.get(universeID);
I use the following code:
/**
* This class is slightly modified version of the Pair class from this thread:
* http://stackoverflow.com/questions/156275/what-is-the-equivalent-of-the-c-pairl-r-in-java
* As suggested in the thread above, I have made first & second to be final members.
* I have made it into an Map.Entry<K,V> type, so it is suitable to be an element
* of any Java Hash map...
*
* @author Dejan Lekic - http://dejan.lekic.org
*/
public class Pair<KeyT, ValueT> implements Map.Entry<KeyT, ValueT> {
protected KeyT first;
protected ValueT second;
public Pair(final KeyT argFirst, final ValueT argSecond) {
super();
this.first = argFirst;
this.second = argSecond;
}
@Override
public int hashCode() {
int hashFirst = (first != null) ? first.hashCode() : 0;
int hashSecond = (second != null) ? second.hashCode() : 0;
return (hashFirst + hashSecond) * hashSecond + hashFirst;
}
@Override
public boolean equals(final Object other) {
if (other instanceof Pair) {
Pair otherPair = (Pair) other;
return ((this.first == otherPair.first
|| (this.first != null && otherPair.first != null
&& this.first.equals(otherPair.first)))
&& (this.second == otherPair.second
|| (this.second != null && otherPair.second != null
&& this.second.equals(otherPair.second))));
} // if
return false;
} // equals() method
@Override
public String toString() {
// previously we used " - " as a separator. Now we will use the 0x1f character, called the UNIT
// SEPARATOR to separate two fields in a String object. See the Sise class for more information.
return first + "\u001f" + second;
}
public KeyT getFirst() {
return first;
}
public void setFirst(final KeyT argFirst) {
this.first = argFirst;
}
public ValueT getSecond() {
return second;
}
public void setSecond(final ValueT argSecond) {
this.second = argSecond;
}
@Override
public ValueT setValue(final ValueT argNewValue) {
ValueT oldValue = second;
second = argNewValue;
return oldValue;
}
@Override
public ValueT getValue() {
return second;
}
@Override
public KeyT getKey() {
return first;
}
} // Pair class
// $Id: Pair.java 149 2012-01-13 12:30:59Z dejan $
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