Spinner auf anderem Layout funktioniert nicht

<activity
            android:name=".favoriten_class"
            android:label="@string/app_name"
            android:screenOrientation="portrait"
            >


            <intent-filter>
                    android:screenOrientation="portrait"/>


                <category android:name="android.intent.category.DEFAULT" />
            </intent-filter>
        </activity>

import android.app.Activity;
import android.os.Bundle;
import android.view.View;
import android.widget.AdapterView;
import android.widget.ArrayAdapter;
import android.widget.Button;
import android.widget.Spinner;
import android.widget.TextView;


/**
 * Created by Allren on 17.03.2015.
 */
public class favoriten_class extends Activity{


    Spinner spinner3;
    TextView tv;






    @Override
    public void setContentView(int favoriten) {


        super.setContentView(R.layout.favoriten);
    }




    @Override
    protected void onCreate(Bundle savedInstanceState) {
        super.onCreate(savedInstanceState);


        setContentView(R.layout.favoriten);


        spinner3=(Spinner)findViewById(R.id.spinner3);
        tv=(TextView)findViewById(R.id.tv);


        ArrayAdapter<CharSequence> adapter= ArrayAdapter.createFromResource(this, R.array.days, android.R.layout.simple_spinner_item);
        spinner3.setAdapter(adapter);
        spinner3.setOnItemSelectedListener(new function());




    }


    public class function implements AdapterView.OnItemSelectedListener {


        @Override
        public void onItemSelected(AdapterView<?> parent, View arg1, int position, long id) {
            String str=parent.getItemAtPosition(position).toString();
            tv.setText(str);
        }


        @Override
        public void onNothingSelected(AdapterView<?> parent) {


        }






    }
}

<?xml version="1.0" encoding="utf-8"?>
<RelativeLayout xmlns:android="http://schemas.android.com/apk/res/android"
    xmlns:tools="http://schemas.android.com/tools"
    android:orientation="vertical"
    android:layout_width="match_parent"
    android:layout_height="match_parent"
    android:background="#BEBEBE"
    android:visibility="visible"
    android:clickable="true"
    tools:context=".MainActivity"


  >




    <TextView
        android:layout_width="wrap_content"
        android:layout_height="wrap_content"
        android:textAppearance="?android:attr/textAppearanceLarge"
        android:text="Favoriten"
        android:id="@+id/textView21"
        android:textSize="30sp"
        android:layout_alignParentTop="true"
        android:layout_centerHorizontal="true"
        android:layout_marginTop="46dp" />


    <Button
        android:layout_width="wrap_content"
        android:layout_height="wrap_content"
        android:text="Favoriten hinzufügen"
        android:id="@+id/button13"
        android:layout_below="@+id/textView21"
        android:layout_centerHorizontal="true"
        android:layout_marginTop="40dp" />


    <Spinner
        android:layout_width="wrap_content"
        android:layout_height="wrap_content"
        android:id="@+id/spinner3"
        android:prompt="@string/spinner_title"
        android:focusableInTouchMode="true"
        android:layout_above="@+id/tv"
        android:layout_alignParentLeft="true"
        android:layout_alignParentStart="true"
        android:layout_toStartOf="@+id/button13"
        android:layout_alignParentRight="true"
        android:layout_alignParentEnd="true" />


    <TextView
        android:layout_width="wrap_content"
        android:layout_height="wrap_content"
        android:textAppearance="?android:attr/textAppearanceMedium"
        android:id="@+id/tv"
        android:layout_centerVertical="true"
        android:layout_alignParentLeft="true"
        android:layout_alignParentStart="true"
 />






</RelativeLayout>

import android.app.Activity;
import android.support.v7.app.ActionBarActivity;
import android.support.v7.app.ActionBar;
import android.support.v4.app.Fragment;
import android.support.v4.app.FragmentManager;
import android.content.Context;
import android.os.Bundle;
import android.view.Gravity;
import android.view.LayoutInflater;
import android.view.Menu;
import android.view.MenuItem;
import android.view.View;
import android.view.ViewGroup;
import android.support.v4.widget.DrawerLayout;
import android.widget.AdapterView;
import android.widget.Button;
import android.widget.EditText;
import android.widget.TextView;
import android.widget.Toast;










public class MainActivity extends ActionBarActivity
        implements NavigationDrawerFragment.NavigationDrawerCallbacks{


    /**
     * Fragment managing the behaviors, interactions and presentation of the navigation drawer.
     */
    private NavigationDrawerFragment mNavigationDrawerFragment;




    /**
     * Used to store the last screen title. For use in {@link #restoreActionBar()}.
     */
    private CharSequence mTitle;


    // Deklarationen Für Lösungen






    @Override
    public void onBackPressed() {
// do something on back.
        return;
    }




   
}




    @Override
    public void onItemSelected(AdapterView<?> parent, View view, int position, long id) {


    }


    @Override
    public void onNothingSelected(AdapterView<?> arg0) {


    }


    /**  Button.OnClickListener btnOnClickListener = new Button.OnClickListener() {
        @Override
        public void onClick(View v) {
            Fragment objFragment = null;


            if (v == button6) {
                TextView textView19 = (TextView) findViewById(R.id.textView19);
                textView19.setText("hello hello!! ");
            }
                 else if (v == btn2)
             {
             newFragment = new Fragment2();
             }
             else if (v == btn3)
             {
             newFragment = new Fragment3();
             }
             else
             {
             newFragment = new StartFragment();
             }
             FragmentManager fragmentManager = getSupportFragmentManager();
             fragmentManager.beginTransaction()
             .replace(R.id.container, objFragment)
             .commit();    */




     // ;
    // }




}