refine the traffic stat

src/main/scala/com/github/shadowsocks/Shadowsocks.scala

@@ -471,7 +471,11 @@ class Shadowsocks
     // initialize timer
     val task = new TimerTask {
       def run() {
-        TrafficMonitor.update()
+        if (state == State.CONNECTED) {
+          TrafficMonitor.update()
+        } else {
+          TrafficMonitor.reset()
+        }
         val pm = getSystemService(Context.POWER_SERVICE).asInstanceOf[PowerManager]
         if (pm.isScreenOn) {
           val trafficStat = getString(R.string.stat_summary).formatLocal(Locale.ENGLISH,

src/main/scala/com/github/shadowsocks/utils/TrafficMonitor.scala

@@ -20,8 +20,8 @@ object TrafficMonitor {
   var rxTotal: Long = 0
 
   def getTraffic(): Traffic = {
-    new Traffic(TrafficStats.getUidTxBytes(uid),
-      TrafficStats.getUidRxBytes(uid), System.currentTimeMillis())
+    new Traffic(TrafficStats.getTotalTxBytes - TrafficStats.getUidTxBytes(uid),
+      TrafficStats.getTotalRxBytes - TrafficStats.getUidRxBytes(uid), System.currentTimeMillis())
   }
 
   def formatTraffic(n: Long): String = {