FindViewByID возвращает Null

public class MainActivity extends ActionBarActivity {
    Button Button_1;
    
    @Override
    protected void onCreate(Bundle savedInstanceState) 
    {
        super.onCreate(savedInstanceState);
        setContentView(R.layout.activity_main);
 
        if (savedInstanceState == null) 
        {
            getSupportFragmentManager().beginTransaction().add(R.id.container, new PlaceholderFragment()).commit();
        }
        
        Button_1 = (Button)findViewById(R.id.button1);
        Button_1.setText("My Text");
    }
}

public static class PlaceholderFragment extends Fragment

setContentView(R.layout.activity_main);

if (savedInstanceState == null) 
        {
            getSupportFragmentManager().beginTransaction().add(R.id.container, new PlaceholderFragment()).commit();
        }

public static class PlaceholderFragment extends Fragment {
 
        public PlaceholderFragment() {
        }
 
        @Override
        public View onCreateView(LayoutInflater inflater, ViewGroup container,
                Bundle savedInstanceState) {
            View rootView = inflater.inflate(R.layout.fragment_main, container,
                    false);
            return rootView;
        }
    }

package com.leibman.helloworld;
 
import android.support.v7.app.ActionBarActivity;
import android.support.v4.app.Fragment;
import android.os.Bundle;
import android.view.LayoutInflater;
import android.view.Menu;
import android.view.MenuItem;
import android.view.MotionEvent;
import android.view.View;
import android.view.View.OnTouchListener;
import android.view.ViewGroup;
import android.widget.Button;
 
public class MainActivity extends ActionBarActivity {
    
    @Override
    protected void onCreate(Bundle savedInstanceState) {
        super.onCreate(savedInstanceState);
        setContentView(R.layout.activity_main);
 
        if (savedInstanceState == null) {
            getSupportFragmentManager().beginTransaction()
                    .add(R.id.container, new PlaceholderFragment()).commit();
        }
    }
 
    @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, 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);
    }
 
    /**
     * A placeholder fragment containing a simple view.
     */
    public static class PlaceholderFragment extends Fragment {
        Button Button_1;
        int Counter = 0;
        
        public PlaceholderFragment() {
        }
 
        @Override
        public View onCreateView(LayoutInflater inflater, ViewGroup container,
                Bundle savedInstanceState) {
            View rootView = inflater.inflate(R.layout.fragment_main, container,
                    false);
            
            Button_1 = (Button)rootView.findViewById(R.id.button1);
            Button_1.setText("Hello World");
            Button_1.setOnTouchListener(On_Touch_Listener);
            
            return rootView;    
        }
        
        OnTouchListener On_Touch_Listener = new OnTouchListener() {
            
            @Override
            public boolean onTouch(View v, MotionEvent event) {
                if (v.getId() == R.id.button1)
                {
                    Button_1.setText(String.valueOf(Counter));
                    Counter++;
                }
                return false;
            }
        };
    }
}