[Tizen.System.Storage] Register eventhandler if it is already existed

Register event handler in the class Storage if eventhandler is already existed.

If at least one event handler is already registered,
the API returns the storage state from a variable within the class.
Otherwise, it retrieves the status externally.

In the previous implementation, an event handler was only registered within class Storage
when it was registered for each storage ID,
and no event handler was registered within class Storage when it was registered by storage type.
As a result of that, when the USB (or SD card) was removed,
it attempted to obtain the state from outside and provided incorrect information
to the application because there is no storage already removed.

Signed-off-by: Unsung Lee <unsung.lee@samsung.com>

src/Tizen.System.Storage/Storage/Storage.cs

@@ -59,7 +59,10 @@ internal Storage(int storageID, Interop.Storage.StorageArea storageType, Interop
             };
         }
 
-        internal Storage(int storageID, Interop.Storage.StorageArea storageType, Interop.Storage.StorageState storagestate, string rootDirectory, Interop.Storage.StorageDevice devicetype, string fstype, string fsuuid, bool primary, int flags)
+        internal Storage(int storageID, Interop.Storage.StorageArea storageType,
+			Interop.Storage.StorageState storagestate, string rootDirectory,
+			Interop.Storage.StorageDevice devicetype, string fstype,
+			string fsuuid, bool primary, int flags, EventHandler eventhandler = null)
         {
             Id = storageID;
             _storagetype = storageType;
@@ -71,6 +74,9 @@ internal Storage(int storageID, Interop.Storage.StorageArea storageType, Interop
             _primary = primary;
             _flags = flags;
             information_set = true;
+            s_stateChangedEventHandler = eventhandler;
+            if (s_stateChangedEventHandler == null)
+                Log.Warn(LogTag, string.Format("Can't register event handler"));
 
             Interop.Storage.ErrorCode err = Interop.Storage.StorageGetTotalSpace(Id, out _totalSpace);
             if (err != Interop.Storage.ErrorCode.None)

src/Tizen.System.Storage/Storage/StorageManager.cs

@@ -55,12 +55,15 @@ public static IEnumerable<Storage> Storages
         private static EventHandler s_ExtendedInternalStorageChangedEventHandler;
         private static Interop.Storage.StorageChangedCallback s_ChangedEventCallback = (int id, Interop.Storage.StorageDevice devicetype, Interop.Storage.StorageState state, string fstype, string fsuuid, string rootDirectory, bool primary, int flags, IntPtr userData) =>
         {
-            Storage storage = new Storage(id, Interop.Storage.StorageArea.External, state, rootDirectory, devicetype, fstype, fsuuid, primary, flags);
-
+            EventHandler eventhandler = null;
             if (devicetype == Interop.Storage.StorageDevice.ExtendedInternalStorage)
-                s_ExtendedInternalStorageChangedEventHandler?.Invoke(storage, EventArgs.Empty);
+                eventhandler = s_ExtendedInternalStorageChangedEventHandler;
             else
-                s_ExternalStorageChangedEventHandler?.Invoke(storage, EventArgs.Empty);
+                eventhandler = s_ExternalStorageChangedEventHandler;
+
+            Storage storage = new Storage(id, Interop.Storage.StorageArea.External,
+			    state, rootDirectory, devicetype, fstype, fsuuid, primary, flags, eventhandler);
+            eventhandler?.Invoke(storage, EventArgs.Empty);
         };
 
         private static void RegisterChangedEvent(StorageArea type)