Switching Activities with different layouts in Android

Ok, so this may sound like a dumb question, but I am trying to figure out how to have an Activity (other than main) control it's layout. I have MainActivity link (on a button click) to another layout. This is all fine.

MainActivity.java:

package com.example.stands;

import android.support.v7.app.ActionBarActivity;
import android.os.Bundle;
import android.os.StrictMode;
import android.view.View;
import android.view.View.OnClickListener;
import android.widget.Button;
import android.widget.EditText;
import android.widget.TextView;

public class MainActivity extends ActionBarActivity {

TextView resultView;
Button button1;

@Override
public void onCreate(Bundle savedInstanceState) {
    super.onCreate(savedInstanceState);
    setContentView(R.layout.activity_main);
    StrictMode.enableDefaults();
    resultView = (TextView) findViewById(R.id.result);

    button1 = (Button) findViewById(R.id.button1);

            //on button click, go to next layout
    button1.setOnClickListener(new OnClickListener() {
        public void onClick(View v) {
            setContentView(R.layout.activity_second_screen);
        }
    });
}
}

Now, in my second Activity, I want to be able to do something like display text on a button click. But when I implement this, nothing happens. I am confused as to how I can make SecondScreen.java control second_activity_screen.xml.

SecondScreen.java:

package com.example.stands;

import android.support.v7.app.ActionBarActivity;
import android.support.v7.app.ActionBar;
import android.support.v4.app.Fragment;
import android.os.Bundle;
import android.os.StrictMode;
import android.view.LayoutInflater;
import android.view.Menu;
import android.view.MenuItem;
import android.view.View;
import android.view.ViewGroup;
import android.view.View.OnClickListener;
import android.widget.Button;
import android.widget.TextView;
import android.os.Build;

public class SecondScreen extends ActionBarActivity {

TextView tv;
Button button1;

@Override
protected void onCreate(Bundle savedInstanceState) {
    super.onCreate(savedInstanceState);
    setContentView(R.layout.activity_second_screen);
    StrictMode.enableDefaults();
    tv = (TextView) findViewById(R.id.textView1);
    button1 = (Button) findViewById(R.id.button1);

            //this is where I want to update text field in second_screen_activity
            //but nothing happens
    button1.setOnClickListener(new OnClickListener() {
        public void onClick(View v) {
            tv.setText("Second Activity Button Pressed");
        }
    });

}

@Override
public boolean onCreateOptionsMenu(Menu menu) {

    // Inflate the menu; this adds items to the action bar if it is present.
    getMenuInflater().inflate(R.menu.second_screen, menu);
    return true;
}

@Override
public boolean onOptionsItemSelected(MenuItem item) {
    // Handle action bar item clicks here. The action bar will
    // automatically handle clicks on the Home/Up button, so long
    // as you specify a parent activity in AndroidManifest.xml.
    int id = item.getItemId();
    if (id == R.id.action_settings) {
        return true;
    }
    return super.onOptionsItemSelected(item);
}

}

second_screen_activity.xml:

<RelativeLayout xmlns:android="http://schemas.android.com/apk/res/android"
xmlns:tools="http://schemas.android.com/tools"
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="com.example.stands.SecondScreen$PlaceholderFragment" >

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

<Button
    android:id="@+id/button1"
    android:layout_width="wrap_content"
    android:layout_height="wrap_content"
    android:layout_alignRight="@+id/textView1"
    android:layout_below="@+id/textView1"
    android:layout_marginTop="142dp"
    android:text="Button" />

</RelativeLayout>

So, when I click a button on activity_main, I go to second_screen_activity and it displays Second Screen. On a button click, I want to change Second Screen to Button Pressed. What am I doing wrong? Thanks guys.