我個人建議使用彈出窗口或定製JWindow代替JPopupMenu作爲後者最初只用於顯示菜單項。它通常適用於其他方面，但不同的最佳做法是使用它。
例如，您的示例中有幾個菜單項作爲自動完成選項 - 如果只有幾個結果，則工作得很好。但是如果有10個呢？如果50？還是500？您必須以某種方式爲這些情況創建額外的解決方法 - 將項目放入滾動窗格（哦，上帝，看起來很醜）或將結果降至最佳（這也不是最好的選項）。
所以我做了一個小例子，使用JWindow作爲AutocompleteField的彈出窗口。這是很簡單，但做了你會期望從它一些基本的東西，你也已經提到的那些：
import javax.swing.*;
import javax.swing.border.EmptyBorder;
import javax.swing.event.DocumentEvent;
import javax.swing.event.DocumentListener;
import java.awt.*;
import java.awt.event.FocusEvent;
import java.awt.event.FocusListener;
import java.awt.event.KeyEvent;
import java.awt.event.KeyListener;
import java.util.ArrayList;
import java.util.Arrays;
import java.util.List;
import java.util.function.Function;
import java.util.stream.Collectors;
/**
* @author Mikle Garin
* @see https://stackoverflow.com/questions/45439231/implementing-autocomplete-with-jtextfield-and-jpopupmenu
*/
public final class AutocompleteField extends JTextField implements FocusListener, DocumentListener, KeyListener
{
/**
* {@link Function} for text lookup.
* It simply returns {@link List} of {@link String} for the text we are looking results for.
*/
private final Function<String, List<String>> lookup;
/**
* {@link List} of lookup results.
* It is cached to optimize performance for more complex lookups.
*/
private final List<String> results;
/**
* {@link JWindow} used to display offered options.
*/
private final JWindow popup;
/**
* Lookup results {@link JList}.
*/
private final JList list;
/**
* {@link #list} model.
*/
private final ListModel model;
/**
* Constructs {@link AutocompleteField}.
*
* @param lookup {@link Function} for text lookup
*/
public AutocompleteField (final Function<String, List<String>> lookup)
{
super();
this.lookup = lookup;
this.results = new ArrayList<>();
final Window parent = SwingUtilities.getWindowAncestor (this);
popup = new JWindow (parent);
popup.setType (Window.Type.POPUP);
popup.setFocusableWindowState (false);
popup.setAlwaysOnTop (true);
model = new ListModel();
list = new JList (model);
popup.add (new JScrollPane (list)
{
@Override
public Dimension getPreferredSize()
{
final Dimension ps = super.getPreferredSize();
ps.width = AutocompleteField.this.getWidth();
return ps;
}
});
addFocusListener (this);
getDocument().addDocumentListener (this);
addKeyListener (this);
}
/**
* Displays autocomplete popup at the correct location.
*/
private void showAutocompletePopup()
{
final Point los = AutocompleteField.this.getLocationOnScreen();
popup.setLocation (los.x, los.y + getHeight());
popup.setVisible (true);
}
/**
* Closes autocomplete popup.
*/
private void hideAutocompletePopup()
{
popup.setVisible (false);
}
@Override
public void focusGained (final FocusEvent e)
{
SwingUtilities.invokeLater (() -> {
if (results.size() > 0)
{
showAutocompletePopup();
}
});
}
private void documentChanged()
{
SwingUtilities.invokeLater (() -> {
// Updating results list
results.clear();
results.addAll (lookup.apply (getText()));
// Updating list view
model.updateView();
list.setVisibleRowCount (Math.min (results.size(), 10));
// Selecting first result
if (results.size() > 0)
{
list.setSelectedIndex (0);
}
// Ensure autocomplete popup has correct size
popup.pack();
// Display or hide popup depending on the results
if (results.size() > 0)
{
showAutocompletePopup();
}
else
{
hideAutocompletePopup();
}
});
}
@Override
public void focusLost (final FocusEvent e)
{
SwingUtilities.invokeLater (this::hideAutocompletePopup);
}
@Override
public void keyPressed (final KeyEvent e)
{
if (e.getKeyCode() == KeyEvent.VK_UP)
{
final int index = list.getSelectedIndex();
if (index != -1 && index > 0)
{
list.setSelectedIndex (index - 1);
}
}
else if (e.getKeyCode() == KeyEvent.VK_DOWN)
{
final int index = list.getSelectedIndex();
if (index != -1 && list.getModel().getSize() > index + 1)
{
list.setSelectedIndex (index + 1);
}
}
else if (e.getKeyCode() == KeyEvent.VK_ENTER)
{
final String text = (String) list.getSelectedValue();
setText (text);
setCaretPosition (text.length());
}
else if (e.getKeyCode() == KeyEvent.VK_ESCAPE)
{
hideAutocompletePopup();
}
}
@Override
public void insertUpdate (final DocumentEvent e)
{
documentChanged();
}
@Override
public void removeUpdate (final DocumentEvent e)
{
documentChanged();
}
@Override
public void changedUpdate (final DocumentEvent e)
{
documentChanged();
}
@Override
public void keyTyped (final KeyEvent e)
{
// Do nothing
}
@Override
public void keyReleased (final KeyEvent e)
{
// Do nothing
}
/**
* Custom list model providing data and bridging view update call.
*/
private class ListModel extends AbstractListModel
{
@Override
public int getSize()
{
return results.size();
}
@Override
public Object getElementAt (final int index)
{
return results.get (index);
}
/**
* Properly updates list view.
*/
public void updateView()
{
super.fireContentsChanged (AutocompleteField.this, 0, getSize());
}
}
/**
* Sample {@link AutocompleteField} usage.
*
* @param args run arguments
*/
public static void main (final String[] args)
{
final JFrame frame = new JFrame ("Sample autocomplete field");
// Sample data list
final List<String> values = Arrays.asList ("Frame", "Dialog", "Label", "Tree", "Table", "List", "Field");
// Simple lookup based on our data list
final Function<String, List<String>> lookup = text -> values.stream()
.filter (v -> !text.isEmpty() && v.toLowerCase().contains (text.toLowerCase()) && !v.equals (text))
.collect (Collectors.toList());
// Autocomplete field itself
final AutocompleteField field = new AutocompleteField (lookup);
field.setColumns (15);
final JPanel border = new JPanel (new BorderLayout());
border.setBorder (new EmptyBorder (50, 50, 50, 50));
border.add (field);
frame.add (border);
frame.setDefaultCloseOperation (WindowConstants.EXIT_ON_CLOSE);
frame.pack();
frame.setLocationRelativeTo (null);
frame.setVisible (true);
}
}
所以在這個例子彈出JWindow本身是不活動（不集中），不能獲得焦點，其強制配置如此。這使我們能夠在JTextField內保持專注並繼續打字。
在此示例中，我們還捕獲字段中的向上/向下箭頭等關鍵事件以導航自動完成結果。 ENTER和ESCAPE用於接受/取消結果選擇。
此代碼也可以稍微改寫爲使用Swing PopupFactory作爲自動完成彈出窗口的來源，但它仍然是由PopupFactory使用，因爲HeavyWeightWindow的essense一樣簡單延伸JWindow，並增加了一些設置。
或使用第三方庫。請參閱https://stackoverflow.com/q/14186955/1076463 – Robin