android: run service in foreground druing computation.

sets edu.berkeley.boinc.client.Monitor as foreground service while client is computing to prevent Android housekeeping to kill it under memory pressure.
consequently is notification preference only applicable to suspended state.
should not have an impact on device's cpu throttling, because only active during computation. As soon as computation suspends, service is put to background.
-GUI not active- client suspension can still occur when suspended for another reason.

android/BOINC/res/values/strings.xml

@@ -159,7 +159,7 @@
 	<string name="prefs_network_daily_xfer_limit_mb_description">Limits the daily data traffic caused by BOINC.</string>
 	<string name="prefs_network_wifi_only_header">Transfer tasks on WiFi only</string>
 	<string name="prefs_autostart_header">Autostart</string>
-	<string name="prefs_show_notification_header">Show notifications</string>
+	<string name="prefs_show_notification_header">Show notification when suspended</string>
 	<string name="prefs_cpu_number_cpus_header">Used CPU cores</string>
 	<string name="prefs_cpu_number_cpus_description">Limits the number of CPU cores BOINC uses for computation.</string>
 	<string name="prefs_cpu_other_load_suspension_header">Pause at CPU usage above</string>

android/BOINC/src/edu/berkeley/boinc/PrefsActivity.java

@@ -237,7 +237,7 @@ public class PrefsActivity extends FragmentActivity {
 			break;
 		case R.string.prefs_show_notification_header: //app pref
 			appPrefs.setShowNotification(isSet);
-			ClientNotification.getInstance(getApplicationContext()).update(); // update notification
+			ClientNotification.getInstance(getApplicationContext()).enable(isSet);
 			updateBoolPref(ID, isSet);
 			updateLayout();
 			break;

android/BOINC/src/edu/berkeley/boinc/client/ClientNotification.java

@@ -21,9 +21,12 @@ public class ClientNotification {
 	private NotificationManager nm;
 	private Integer notificationId;
 	private PendingIntent contentIntent;
-
+	
 	private int mOldComputingStatus = -1;
 	private int mOldSuspendReason = -1;
+	// debug foreground state by running
+	// adb shell: dumpsys activity services edu.berkeley.boinc
+	private boolean foreground = false;
 
 	/**
 	 * Returns a reference to a singleton ClientNotification object.
@@ -49,30 +52,35 @@ public class ClientNotification {
 	/**
 	 * Updates notification with client's current status
 	 */
-	public synchronized void update() {
-		// check whether notification is allowed in preferences	
-		if (!Monitor.getAppPrefs().getShowNotification()) {
-			nm.cancel(notificationId);
-			clientNotification.mOldComputingStatus = -1;
-			return;
-		}
-
-		// try to get current client status from monitor
-		ClientStatus updatedStatus;
-		try{
-			updatedStatus  = Monitor.getClientStatus();
-		} catch (Exception e){
-			if(Logging.WARNING) Log.w(Logging.TAG,"ClientNotification: Could not load data, clientStatus not initialized.");
-			return;
-		}
+	public synchronized void update(ClientStatus updatedStatus, Monitor monitorService) {
 		
-		// update notification
+		// update notification, only after change in status
 		if (clientNotification.mOldComputingStatus == -1 
 				|| updatedStatus.computingStatus.intValue() != clientNotification.mOldComputingStatus
 				|| (updatedStatus.computingStatus == ClientStatus.COMPUTING_STATUS_SUSPENDED
 				&& updatedStatus.computingSuspendReason != clientNotification.mOldSuspendReason)) {
 			
-			nm.notify(notificationId, buildNotification(updatedStatus));
+			if(updatedStatus.computingStatus == ClientStatus.COMPUTING_STATUS_COMPUTING) {
+				// computing! set service as foreground
+				monitorService.startForeground(notificationId, buildNotification(updatedStatus));
+				if(Logging.DEBUG) Log.d(Logging.TAG,"ClientNotification.update() start service as foreground.");
+				foreground = true;
+			} else {
+				// not computing, set service as background
+				if(foreground) {
+					foreground = false;
+					monitorService.stopForeground(true);
+					if(Logging.DEBUG) Log.d(Logging.TAG,"ClientNotification.update() stop service as foreground.");
+				}
+				// check whether notification is allowed in preferences	
+				if (!Monitor.getAppPrefs().getShowNotification()) {
+					enable(false);
+					return;
+				}
+
+				nm.notify(notificationId, buildNotification(updatedStatus));
+			}
+			
 			
 			// save status for comparison next time
 			clientNotification.mOldComputingStatus = updatedStatus.computingStatus;
@@ -80,6 +88,30 @@ public class ClientNotification {
 		}
 	}
 	
+	// called after change in notification preference
+	public synchronized void enable(Boolean enable) {
+		if(Logging.DEBUG) Log.d(Logging.TAG,"ClientNotification.enable() " + enable);
+		if(foreground) {
+			// foreground notification mandatory, do not change
+			if(Logging.DEBUG) Log.d(Logging.TAG,"ClientNotification.enable() service in foreground, do not change.");
+		} else {
+			// service in background, notification behavior configurable
+			if(enable){
+				try{
+					ClientStatus status = Monitor.getClientStatus();
+					nm.notify(notificationId, buildNotification(status));
+					// save status for comparison next time
+					clientNotification.mOldComputingStatus = status.computingStatus;
+					clientNotification.mOldSuspendReason = status.computingSuspendReason;
+				} catch (Exception e) {if(Logging.WARNING) Log.w(Logging.TAG,"ClientNotification.enable() failed!");}
+				
+			} else {
+				nm.cancel(notificationId);
+				clientNotification.mOldComputingStatus = -1;
+			}
+		}
+	}
+	
 	// cancels notification, called during client shutdown
 	public synchronized void cancel() {
 		nm.cancel(notificationId);

android/BOINC/src/edu/berkeley/boinc/client/Monitor.java

@@ -370,7 +370,7 @@ public class Monitor extends Service {
 				if( (status != null) && (state != null) && (state.results != null) && (state.projects != null) && (transfers != null) && (state.host_info != null)) {
 					Monitor.getClientStatus().setClientStatus(status, state.results, state.projects, transfers, state.host_info);
 					// Update status bar notification
-					ClientNotification.getInstance(getApplicationContext()).update();
+					ClientNotification.getInstance(getApplicationContext()).update(Monitor.getClientStatus(), this);
 				} else {
 					if(Logging.ERROR) Log.e(Logging.TAG, "readClientStatus(): connection problem");
 				}