我正在使用进度条（圆圈），而我的数据正在加载从数据库在启动画面。我用的进度条在xml中使用其标签...但在活动中，它是不旋转...建议帮助...有什么问题吗？

xml:


          <?xml version="1.0" encoding="utf-8"?>
        <RelativeLayout xmlns:android="http://schemas.android.com/apk/res/android"
            android:layout_width="match_parent"
            android:layout_height="match_parent" >

            <ImageView
                android:id="@+id/imgLogo"
                android:layout_width="wrap_content"
                android:layout_height="wrap_content"
                android:layout_centerInParent="true"
                android:background="@drawable/splash" />

            <TextView
                android:id="@+id/textView1"
                android:layout_width="wrap_content"
                android:layout_height="wrap_content"
                android:layout_below="@+id/loading"
                android:layout_centerHorizontal="true"
                android:gravity="center_horizontal"
                android:text="Loading data..."
                android:visibility="visible"
                android:textAppearance="?android:attr/textAppearanceLarge" />

           <ProgressBar
            android:id="@+id/loading"
            android:layout_width="wrap_content"
            android:layout_height="wrap_content"
            android:layout_alignParentTop="true"
            android:layout_centerHorizontal="true"
            android:layout_marginTop="92dp"
            android:gravity="center"
            android:indeterminateDrawable="@drawable/custom_bar" />
    </RelativeLayout>

    Java: 

    public class SplashScreen extends Activity {
        static String DATABASE_NAME = "ItemDB";
        static DBACESS mDbAccess = null;
        public static SQLiteDatabase mDB;
        public static ListItems objitem;
        private static int SPLASH_TIME_OUT = 100;
        private PackageManager packageManager = null;
        static DataEntryClass data = new DataEntryClass();
        static List<ItemClass> item_table;
        ProgressBar progressBar;
        @Override
        protected void onCreate(Bundle savedInstanceState) {
            super.onCreate(savedInstanceState);
            requestWindowFeature(Window.FEATURE_NO_TITLE);
            getWindow().setFlags(WindowManager.LayoutParams.FLAG_FULLSCREEN,
                    WindowManager.LayoutParams.FLAG_FULLSCREEN);
            setContentView(R.layout.activity_splash);
            progressBar = (ProgressBar) findViewById(R.id.loading);
            // ////////////////////////
            /////////////////////////
            CheckConnectionState(getApplicationContext());
            packageManager = getPackageManager();

            if (objitem == null)
                objitem = new ListItems(getApplicationContext(), mDB);

            if (!objitem.ItemsExist(mDB))
                try {
                    data.addItems(getApplicationContext());
                } catch (Exception e) {
                    // TODO: handle exception
                }

            new Handler().postDelayed(new Runnable() {

                @Override
                public void run() {

                    data.getNewUpdates(getApplicationContext(), packageManager);
                    item_table = new ArrayList<ItemClass>();
                    item_table = objitem.LoadItems(mDB);

                    Intent i = new Intent(SplashScreen.this, TabActivity.class);
                    startActivity(i);

                    // close this activity
                    finish();
                }
            }, SPLASH_TIME_OUT);
        }


        public static void CheckConnectionState(Context ct) {
            try {

                if (mDB == null || !mDB.isOpen()) {
                    DBACESS.DATABASE_NAME = DATABASE_NAME;
                    mDbAccess = new DBACESS(ct);
                    mDB = mDbAccess.getReadableDatabase();
                }
            } catch (Exception e) {

            }
        }
    }

custom_bar.xml:
<?xml version="1.0" encoding="utf-8"?>
<rotate xmlns:android="http://schemas.android.com/apk/res/android"
android:fromDegrees="0"
android:pivotX="50%"
android:pivotY="50%"
android:toDegrees="360"
android:repeatCount="infinite"
android:drawable="@drawable/menu" >
</rotate>