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a917f100 NR |
1 | package be.nikiroo.utils.ui; |
2 | ||
3 | import java.awt.event.ActionEvent; | |
4 | import java.awt.event.ActionListener; | |
5 | import java.util.LinkedList; | |
6 | import java.util.Queue; | |
7 | ||
8 | import javax.swing.JPanel; | |
9 | ||
10 | /** | |
11 | * A {@link JPanel} with the default {@link ActionListener} add/remove/fire | |
12 | * methods. | |
13 | * <p> | |
14 | * Note that it will queue all events until at least one listener comes (or | |
15 | * comes back!); this first (or at least currently unique) listener will drain | |
16 | * the queue. | |
17 | * | |
18 | * @author niki | |
19 | */ | |
20 | public class ListenerPanel extends JPanel { | |
21 | private static final long serialVersionUID = 1L; | |
22 | ||
23 | /** Waiting queue until at least one listener is here to get the events. */ | |
24 | private final Queue<ActionEvent> waitingQueue; | |
25 | ||
26 | /** | |
27 | * Create a new {@link ListenerPanel}. | |
28 | */ | |
29 | public ListenerPanel() { | |
30 | waitingQueue = new LinkedList<ActionEvent>(); | |
31 | } | |
32 | ||
33 | /** | |
34 | * Check that this {@link ListenerPanel} currently has | |
35 | * {@link ActionListener}s that listen on it. | |
36 | * | |
37 | * @return TRUE if it has | |
38 | */ | |
39 | public synchronized boolean hasListeners() { | |
40 | return listenerList.getListenerList().length > 1; | |
41 | } | |
42 | ||
43 | /** | |
44 | * Check how many events are currently waiting for an | |
45 | * {@link ActionListener}. | |
46 | * | |
47 | * @return the number of waiting events (can be 0) | |
48 | */ | |
49 | public synchronized int getWaitingEventCount() { | |
50 | return waitingQueue.size(); | |
51 | } | |
52 | ||
53 | /** | |
54 | * Adds the specified action listener to receive action events from this | |
55 | * {@link ListenerPanel}. | |
56 | * | |
57 | * @param listener | |
58 | * the action listener to be added | |
59 | */ | |
60 | public synchronized void addActionListener(ActionListener listener) { | |
61 | if (!hasListeners()) { | |
62 | while (!waitingQueue.isEmpty()) { | |
63 | listener.actionPerformed(waitingQueue.remove()); | |
64 | } | |
65 | } | |
66 | ||
67 | listenerList.add(ActionListener.class, listener); | |
68 | } | |
69 | ||
70 | /** | |
71 | * Removes the specified action listener so that it no longer receives | |
72 | * action events from this {@link ListenerPanel}. | |
73 | * | |
74 | * @param listener | |
75 | * the action listener to be removed | |
76 | */ | |
77 | public synchronized void removeActionListener(ActionListener listener) { | |
78 | listenerList.remove(ActionListener.class, listener); | |
79 | } | |
80 | ||
81 | /** | |
82 | * Notify the listeners of an action. | |
83 | * | |
84 | * @param listenerCommand | |
85 | * A string that may specify a command (possibly one of several) | |
86 | * associated with the event | |
87 | */ | |
88 | protected synchronized void fireActionPerformed(String listenerCommand) { | |
89 | ActionEvent e = new ActionEvent(this, ActionEvent.ACTION_PERFORMED, | |
90 | listenerCommand); | |
91 | ||
92 | ActionListener[] listeners = getListeners(ActionListener.class); | |
93 | if (listeners.length > 0) { | |
94 | for (ActionListener action : listeners) { | |
95 | action.actionPerformed(e); | |
96 | } | |
97 | } else { | |
98 | waitingQueue.add(e); | |
99 | } | |
100 | } | |
101 | } |