the codes are not working in the second xml file

i am just working on a test app.

this is the xml file of the home page.

      <RelativeLayout xmlns:android="http://ift.tt/nIICcg"
    xmlns:tools="http://ift.tt/LrGmb4"
    android:layout_width="match_parent"
    android:layout_height="match_parent"
    android:paddingBottom="@dimen/activity_vertical_margin"
    android:paddingLeft="@dimen/activity_horizontal_margin"
    android:paddingRight="@dimen/activity_horizontal_margin"
    android:paddingTop="@dimen/activity_vertical_margin"
    tools:context=".MainActivityTEST2" >

    <TextView
        android:id="@+id/textView1"
        android:layout_width="wrap_content"
        android:layout_height="wrap_content"
        android:text="@string/hello_world" />

    <Button
        android:id="@+id/button12"
        android:layout_width="wrap_content"
        android:layout_height="wrap_content"
        android:layout_below="@+id/textView1"
        android:layout_centerHorizontal="true"
        android:layout_marginTop="72dp"
        android:text="Button12" />

       </RelativeLayout>

i have added a button listener to go to other page. here is my code for that.

 package com.example.test2;

import android.os.Bundle;
import android.app.Activity;
import android.view.Menu;
import android.view.View;
import android.widget.Button;
import android.widget.EditText;

public class MainActivityTEST2 extends Activity {

    Button but;

    @Override
    protected void onCreate(Bundle savedInstanceState) {
        super.onCreate(savedInstanceState);
        setContentView(R.layout.activity_main_activity_test2);
    but=(Button)findViewById(R.id.button12);
    but.setOnClickListener(new View.OnClickListener() {

        @Override
        public void onClick(View arg0) {
            // TODO Auto-generated method stub
            setContentView(R.layout.activity123);
        }
    });

    }


    @Override
    public boolean onCreateOptionsMenu(Menu menu) {
        // Inflate the menu; this adds items to the action bar if it is present.
        getMenuInflater().inflate(R.menu.main_activity_test2, menu);
        return true;
    }

when i add a button listener in the second page to display text in the textfield, nothing works.

xml file of the second page

<?xml version="1.0" encoding="utf-8"?>
<LinearLayout xmlns:android="http://ift.tt/nIICcg"
    android:layout_width="match_parent"
    android:layout_height="match_parent"
    android:orientation="vertical" >

    <Button
        android:id="@+id/button2"
        android:layout_width="wrap_content"
        android:layout_height="wrap_content"
        android:text="Button" />

    <EditText
        android:id="@+id/edittext1"
        android:layout_width="match_parent"
        android:layout_height="wrap_content"
        android:ems="10" >

        <requestFocus />
    </EditText>

</LinearLayout>

when i add a button listerner to display text in the textfiled, nothing works. the app neighter stops working nor does anything after that.

my second window's java content is

import android.app.Activity;
import android.os.Bundle;
import android.view.Menu;
import android.view.View;
import android.widget.Button;
import android.widget.EditText;

import com.example.test2.R;



public class activity_main_activty_test2 extends Activity {
    Button but2;
    EditText edit1;

     @Override
        protected void onCreate(Bundle savedInstanceState) {
            super.onCreate(savedInstanceState);
            setContentView(R.layout.activity123);

            edit1=(EditText)findViewById(R.id.edittext1);
            but2=(Button)findViewById(R.id.button2);
            but2.setOnClickListener(new View.OnClickListener() {

                @Override
                public void onClick(View v) {
                    // TODO Auto-generated method stub
                    edit1.setText("hellow");
                }
            });

          }



     @Override
        public boolean onCreateOptionsMenu(Menu menu) {
            // Inflate the menu; this adds items to the action bar if it is present.
            getMenuInflater().inflate(R.menu.main_activity_test2, menu);
            return true;
        }
}

am i missing something. do i have to address something. please help i am just a biggener.