Merge commit 'ee020e75a5de0c1e54557db79f77edc50e05ea04'

[fanfix.git] / src / be / nikiroo / utils / ui / ListenerPanel.java

diff --git a/src/be/nikiroo/utils/ui/ListenerPanel.java b/src/be/nikiroo/utils/ui/ListenerPanel.java
new file mode 100644 (file)
index 0000000..144cdd2
--- /dev/null
+++ b/src/be/nikiroo/utils/ui/ListenerPanel.java
@@ -0,0 +1,101 @@
+package be.nikiroo.utils.ui;
+
+import java.awt.event.ActionEvent;
+import java.awt.event.ActionListener;
+import java.util.LinkedList;
+import java.util.Queue;
+
+import javax.swing.JPanel;
+
+/**
+ * A {@link JPanel} with the default {@link ActionListener} add/remove/fire
+ * methods.
+ * <p>
+ * Note that it will queue all events until at least one listener comes (or
+ * comes back!); this first (or at least currently unique) listener will drain
+ * the queue.
+ * 
+ * @author niki
+ */
+public class ListenerPanel extends JPanel {
+       private static final long serialVersionUID = 1L;
+
+       /** Waiting queue until at least one listener is here to get the events. */
+       private final Queue<ActionEvent> waitingQueue;
+
+       /**
+        * Create a new {@link ListenerPanel}.
+        */
+       public ListenerPanel() {
+               waitingQueue = new LinkedList<ActionEvent>();
+       }
+
+       /**
+        * Check that this {@link ListenerPanel} currently has
+        * {@link ActionListener}s that listen on it.
+        * 
+        * @return TRUE if it has
+        */
+       public synchronized boolean hasListeners() {
+               return listenerList.getListenerList().length > 1;
+       }
+
+       /**
+        * Check how many events are currently waiting for an
+        * {@link ActionListener}.
+        * 
+        * @return the number of waiting events (can be 0)
+        */
+       public synchronized int getWaitingEventCount() {
+               return waitingQueue.size();
+       }
+
+       /**
+        * Adds the specified action listener to receive action events from this
+        * {@link ListenerPanel}.
+        *
+        * @param listener
+        *            the action listener to be added
+        */
+       public synchronized void addActionListener(ActionListener listener) {
+               if (!hasListeners()) {
+                       while (!waitingQueue.isEmpty()) {
+                               listener.actionPerformed(waitingQueue.remove());
+                       }
+               }
+
+               listenerList.add(ActionListener.class, listener);
+       }
+
+       /**
+        * Removes the specified action listener so that it no longer receives
+        * action events from this {@link ListenerPanel}.
+        *
+        * @param listener
+        *            the action listener to be removed
+        */
+       public synchronized void removeActionListener(ActionListener listener) {
+               listenerList.remove(ActionListener.class, listener);
+       }
+
+       /**
+        * Notify the listeners of an action.
+        * 
+        * @param listenerCommand
+        *            A string that may specify a command (possibly one of several)
+        *            associated with the event
+        */
+       protected synchronized void fireActionPerformed(String listenerCommand) {
+               ActionEvent e = new ActionEvent(this, ActionEvent.ACTION_PERFORMED,
+                               listenerCommand);
+
+               ActionListener[] listeners = getListeners(ActionListener.class);
+               if (listeners.length > 0) {
+                       for (ActionListener action : listeners) {
+                               action.actionPerformed(e);
+                       }
+               } else {
+                       waitingQueue.add(e);
+               }
+       }
+}