Java.lang.IllegalStateException: attempt to re-open an already-closed?

I got error from my Sqlite Android. I have code like this:

public int UpdatePhotoUser(String foto_user, int metode) {

        SQLiteDatabase db = this.getWritableDatabase();
        ContentValues values = new ContentValues();
        int update = 0;

        if (metode == 1) {
            values.put(Variabel.KEY_USER_PHOTO, foto_user);
            try {
                update = db.update(
                        Variabel.TABLE_USER,
                        values, null, null);
            } catch (android.database.sqlite.SQLiteException e) {

            }
        } else if (metode == 2 && getUserDetails(Variabel.KEY_USER_PHOTO).equals(foto_user)) {
            values.put(Variabel.KEY_USER_PHOTO, "");
            try {
                update = db.update(
                        Variabel.TABLE_USER,
                        values, null, null);
            } catch (android.database.sqlite.SQLiteException e) {

            }
        }

        db.close();
        return update;
    }

And I have Error at last line:

update = db.update(
                            Variabel.TABLE_USER,
                            values, null, null);

This the eror:

Java.lang.IllegalStateException: attempt to re-open an already-closed object: SQLiteDatabase: /data/data/com.ad.kamardagang.newseditor/databases/DB_KAMAR_DAGANG
            at android.database.sqlite.SQLiteClosable.acquireReference(SQLiteClosable.java:55)
            at android.database.sqlite.SQLiteDatabase.updateWithOnConflict(SQLiteDatabase.java:1545)
            at android.database.sqlite.SQLiteDatabase.update(SQLiteDatabase.java:1522)
            at com.ad.kamardagang.newseditor.database_content.DatabaseHandler.UpdatePhotoUser(DatabaseHandler.java:613)
            at com.ad.kamardagang.newseditor.fragments.PhotoUserFragment.removeRespone(PhotoUserFragment.java:985)
            at com.ad.kamardagang.newseditor.fragments.PhotoUserFragment.access$600(PhotoUserFragment.java:62)
            at com.ad.kamardagang.newseditor.fragments.PhotoUserFragment$12.onResponse(PhotoUserFragment.java:879)
            at com.ad.kamardagang.newseditor.fragments.PhotoUserFragment$12.onResponse(PhotoUserFragment.java:875)
            at com.android.volley.toolbox.StringRequest.deliverResponse(StringRequest.java:60)
            at com.android.volley.toolbox.StringRequest.deliverResponse(StringRequest.java:30)
            at com.android.volley.ExecutorDelivery$ResponseDeliveryRunnable.run(ExecutorDelivery.java:99)
            at android.os.Handler.handleCallback(Handler.java:739)
            at android.os.Handler.dispatchMessage(Handler.java:95)
            at android.os.Looper.loop(Looper.java:135)
            at android.app.ActivityThread.main(ActivityThread.java:5254)
            at java.lang.reflect.Method.invoke(Native Method)
            at java.lang.reflect.Method.invoke(Method.java:372)
            at com.android.internal.os.ZygoteInit$MethodAndArgsCaller.run(ZygoteInit.java:903)
            at com.android.internal.os.ZygoteInit.main(ZygoteInit.java:698)

when. I first call metode UpdatePhotoUser(String foto_user, int metode), but on second call its error. so how to fix it ?