Renew the wake lock every 30min

Signed-off-by: goapunk <noobie@goapunks.net>

bramble-android/src/main/java/org/briarproject/bramble/util/ScheduledExecutorServiceWakeLock.java

@@ -0,0 +1,47 @@
+package org.briarproject.bramble.util;
+
+import android.content.Context;
+
+import java.util.concurrent.Executors;
+import java.util.concurrent.ScheduledExecutorService;
+import java.util.concurrent.ThreadFactory;
+import java.util.concurrent.TimeUnit;
+
+public class ScheduledExecutorServiceWakeLock {
+
+	final Context appContext;
+
+	private static final ThreadFactory THREAD_FACTORY = new ThreadFactory() {
+		@Override
+		public Thread newThread(Runnable r) {
+			Thread t = new Thread(r);
+			t.setDaemon(true);
+			return t;
+		}
+	};
+
+	private ScheduledExecutorService scheduledExecutorService = null; // Locking: this
+	private Runnable runnable;
+
+	public ScheduledExecutorServiceWakeLock(Context appContext) {
+		this.appContext = appContext;
+	}
+
+	public void setRunnable(Runnable r){
+		runnable = r;
+	}
+
+	public synchronized void setAlarm(long delay, TimeUnit unit) {
+		if(runnable == null)
+			return;
+		if (scheduledExecutorService == null)
+			scheduledExecutorService = Executors.newSingleThreadScheduledExecutor(THREAD_FACTORY);
+		scheduledExecutorService.schedule(runnable, delay, unit);
+	}
+
+	public synchronized void cancelAlarm() {
+		if (scheduledExecutorService == null) throw new IllegalStateException();
+		scheduledExecutorService.shutdownNow();
+		scheduledExecutorService = null;
+	}
+}