Add PingManager.pingServerIfNecessary()

which is basically the body of the pingServerRunnable available as
public part of the API. The intention is to allow 3rd party
components (e.g. Android's AlarmManager) to trigger the code.

smack-extensions/src/main/java/org/jivesoftware/smackx/ping/PingManager.java

@@ -317,70 +317,76 @@ public class PingManager extends Manager {
         }
     }
 
-    private final Runnable pingServerRunnable = new Runnable() {
-        private static final int DELTA = 1000; // 1 seconds
-        private static final int TRIES = 3; // 3 tries
-
-        public void run() {
-            LOGGER.fine("ServerPingTask run()");
-            XMPPConnection connection = connection();
-            if (connection == null) {
-                // connection has been collected by GC
-                // which means we can stop the thread by breaking the loop
+    /**
+     * Ping the server if deemed necessary because automatic server pings are
+     * enabled ({@link #setPingInterval(int)}) and the ping interval has expired.
+     */
+    public synchronized void pingServerIfNecessary() {
+        final int DELTA = 1000; // 1 seconds
+        final int TRIES = 3; // 3 tries
+        final XMPPConnection connection = connection();
+        if (connection == null) {
+            // connection has been collected by GC
+            // which means we can stop the thread by breaking the loop
+            return;
+        }
+        if (pingInterval <= 0) {
+            // Ping has been disabled
+            return;
+        }
+        long lastStanzaReceived = connection.getLastStanzaReceived();
+        if (lastStanzaReceived > 0) {
+            long now = System.currentTimeMillis();
+            // Delta since the last stanza was received
+            int deltaInSeconds = (int)  ((now - lastStanzaReceived) / 1000);
+            // If the delta is small then the ping interval, then we can defer the ping
+            if (deltaInSeconds < pingInterval) {
+                maybeSchedulePingServerTask(deltaInSeconds);
                 return;
             }
-            if (pingInterval <= 0) {
-                // Ping has been disabled
-                return;
-            }
-            long lastStanzaReceived = connection.getLastStanzaReceived();
-            if (lastStanzaReceived > 0) {
-                long now = System.currentTimeMillis();
-                // Delta since the last stanza was received
-                int deltaInSeconds = (int)  ((now - lastStanzaReceived) / 1000);
-                // If the delta is small then the ping interval, then we can defer the ping
-                if (deltaInSeconds < pingInterval) {
-                    maybeSchedulePingServerTask(deltaInSeconds);
-                    return;
-                }
-            }
-            if (connection.isAuthenticated()) {
-                boolean res = false;
+        }
+        if (connection.isAuthenticated()) {
+            boolean res = false;
 
-                for (int i = 0; i < TRIES; i++) {
-                    if (i != 0) {
-                        try {
-                            Thread.sleep(DELTA);
-                        } catch (InterruptedException e) {
-                            // We received an interrupt
-                            // This only happens if we should stop pinging
-                            return;
-                        }
-                    }
+            for (int i = 0; i < TRIES; i++) {
+                if (i != 0) {
                     try {
-                        res = pingMyServer(false);
-                    }
-                    catch (SmackException e) {
-                        LOGGER.log(Level.WARNING, "SmackError while pinging server", e);
-                        res = false;
-                    }
-                    // stop when we receive a pong back
-                    if (res) {
-                        break;
+                        Thread.sleep(DELTA);
+                    } catch (InterruptedException e) {
+                        // We received an interrupt
+                        // This only happens if we should stop pinging
+                        return;
                     }
                 }
-                LOGGER.fine("ServerPingTask res=" + res);
-                if (!res) {
-                    for (PingFailedListener l : pingFailedListeners) {
-                        l.pingFailed();
-                    }
-                } else {
-                    // Ping was successful, wind-up the periodic task again
-                    maybeSchedulePingServerTask();
+                try {
+                    res = pingMyServer(false);
+                }
+                catch (SmackException e) {
+                    LOGGER.log(Level.WARNING, "SmackError while pinging server", e);
+                    res = false;
+                }
+                // stop when we receive a pong back
+                if (res) {
+                    break;
+                }
+            }
+            if (!res) {
+                for (PingFailedListener l : pingFailedListeners) {
+                    l.pingFailed();
                 }
             } else {
-                LOGGER.warning("ServerPingTask: XMPPConnection was not authenticated");
+                // Ping was successful, wind-up the periodic task again
+                maybeSchedulePingServerTask();
             }
+        } else {
+            LOGGER.warning("XMPPConnection was not authenticated");
+        }
+    }
+
+    private final Runnable pingServerRunnable = new Runnable() {
+        public void run() {
+            LOGGER.fine("ServerPingTask run()");
+            pingServerIfNecessary();
         }
     };