Error building signed apk in android studio: This class should provide default constructor

Error: This class should provide a default constructor (a public constructor with no arguments) (com.tasbih.counter.tasbihcounter.RegistrationAdapterr) [Instantiatable]

This error occurs when i try to build signed apk, but in debug mode the app is working fine. Please help.

package com.tasbih.counter.tasbihcounter;

import android.content.ContentValues;
import android.content.Context;
import android.database.Cursor;
import android.database.sqlite.SQLiteDatabase;

public class RegistrationAdapterr {
SQLiteDatabase database_ob;
RegistrationOpenHelperr openHelper_ob;
Context context;

public RegistrationAdapterr(Context c) {
    context = c;
}


public RegistrationAdapterr opnToRead() {

    openHelper_ob = new RegistrationOpenHelperr(context,
            openHelper_ob.DATABASE_NAME, null, openHelper_ob.VERSION);
    database_ob = openHelper_ob.getReadableDatabase();

    return this;

}

public RegistrationAdapterr opnToWrite() {
    openHelper_ob = new RegistrationOpenHelperr(context,
            openHelper_ob.DATABASE_NAME, null, openHelper_ob.VERSION);
    database_ob = openHelper_ob.getWritableDatabase();
    return this;

}

public void Close() {
    database_ob.close();
}

public long insertDetails(String fname, String lname, Integer count) {
    ContentValues contentValues = new ContentValues();
    contentValues.put(openHelper_ob.FNAME, fname);
    contentValues.put(openHelper_ob.LNAME, lname);
    contentValues.put(openHelper_ob.COUNT, count);
    opnToWrite();
    long val = database_ob.insert(openHelper_ob.TABLE_NAME, null,
            contentValues);
    Close();
    return val;

}

public Cursor queryName() {
    String[] cols = { openHelper_ob.KEY_ID, openHelper_ob.FNAME,
            openHelper_ob.LNAME, openHelper_ob.COUNT };
    opnToWrite();
    Cursor c = database_ob.query(openHelper_ob.TABLE_NAME, cols, null,
            null, null, null, null);

    return c;
}

public Cursor queryAll(int nameId) {
    String[] cols = { openHelper_ob.KEY_ID, openHelper_ob.FNAME,
            openHelper_ob.LNAME, openHelper_ob.COUNT };
    opnToWrite();
    Cursor c = database_ob.query(openHelper_ob.TABLE_NAME, cols,
            openHelper_ob.KEY_ID + "=" + nameId, null, null, null, null);

    return c;

}

public long updateldetail(int rowId, String fname, String lname, Integer count) {
    ContentValues contentValues = new ContentValues();
    contentValues.put(openHelper_ob.FNAME, fname);
    contentValues.put(openHelper_ob.LNAME, lname);
    contentValues.put(openHelper_ob.COUNT, count);
    opnToWrite();
    long val = database_ob.update(openHelper_ob.TABLE_NAME, contentValues,
            openHelper_ob.KEY_ID + "=" + rowId, null);
    Close();
    return val;
}

public int deletOneRecord(int rowId) {
    // TODO Auto-generated method stub
    opnToWrite();
    int val = database_ob.delete(openHelper_ob.TABLE_NAME,
            openHelper_ob.KEY_ID + "=" + rowId, null);
    Close();
    return val;
}

}