优化 dns prefetch

Author: YangSen-qn

library/src/main/java/com/qiniu/android/common/FixedZone.java

@@ -109,6 +109,7 @@ private ZonesInfo createZonesInfo(String[] upDomains,
         }
         ArrayList<ZoneInfo> zoneInfoList = new ArrayList<ZoneInfo>();
         zoneInfoList.add(zoneInfo);
+
         return new ZonesInfo(zoneInfoList);
     }
 

library/src/main/java/com/qiniu/android/http/dns/DnsPrefetcher.java

@@ -321,9 +321,11 @@ public void complete(int code, ResponseInfo responseInfo, UploadRegionRequestMet
 
         ZonesInfo autoZonesInfo = currentZone.getZonesInfo(token);
         ArrayList<String> autoHosts = new ArrayList<>();
-        for (ZoneInfo zoneInfo : autoZonesInfo.zonesInfo) {
-            if (zoneInfo != null && zoneInfo.allHosts != null){
-                autoHosts.addAll(zoneInfo.allHosts);
+        if (autoZonesInfo != null && autoZonesInfo.zonesInfo != null && autoZonesInfo.zonesInfo.size() > 0) {
+            for (ZoneInfo zoneInfo : autoZonesInfo.zonesInfo) {
+                if (zoneInfo != null && zoneInfo.allHosts != null) {
+                    autoHosts.addAll(zoneInfo.allHosts);
+                }
             }
         }
         return autoHosts.toArray(new String[0]);