安卓菜鸟 这两个按钮加入同一个页面，加入第二个按钮之后运行时只有第二个按钮可点击 第一个按钮点击没反应，求问是怎么回事？

package com.example.liuyuteng;

import android.app.Activity;
import android.content.Intent;
import android.os.Bundle;
import android.view.Menu;
import android.view.MenuItem;
import android.view.View;
import android.view.View.OnClickListener;
import android.widget.Button;
import android.widget.Toast;

public class SecondActivity extends Activity{

@Override
protected void onCreate(Bundle savedInstanceState) {
    super.onCreate(savedInstanceState);
    setContentView(R.layout.two);
    Button button2=(Button)findViewById(R.id.button2);
    button2.setOnClickListener(new OnClickListener(){
    public void onClick(View v){
        Intent intent=new Intent(SecondActivity.this,ThreeActivity.class);
        startActivity(intent);
    }
});
    super.onCreate(savedInstanceState);
    setContentView(R.layout.two);
    Button button3=(Button)findViewById(R.id.button3);
    button3.setOnClickListener(new OnClickListener(){
    public void onClick(View v){
        Intent intent=new Intent(SecondActivity.this,FourActivity.class);
        startActivity(intent);
    }
});  
} 



@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);
}

}

这都是基础的基础了，setContentView两次，真的是.......
@Override
protected void onCreate(Bundle savedInstanceState) {
super.onCreate(savedInstanceState);
setContentView(R.layout.two); <------
Button button2=(Button)findViewById(R.id.button2);
button2.setOnClickListener(new OnClickListener(){
public void onClick(View v){
Intent intent=new Intent(SecondActivity.this,ThreeActivity.class);
startActivity(intent);
}
});
super.onCreate(savedInstanceState);<----
setContentView(R.layout.two);<------ 设置两次layout，等于是重新设置了一次，前面设置的都不起作用了把这里两行去掉
Button button3=(Button)findViewById(R.id.button3);
button3.setOnClickListener(new OnClickListener(){
public void onClick(View v){
Intent intent=new Intent(SecondActivity.this,FourActivity.class);
startActivity(intent);
}
});

}