一个很简单的程序，一直报空指针错误，刚开始学，百度自己试了很久都改不出来，求大神指点

Question

package com.sample.test02;

import android.app.Activity;
import android.os.Bundle;
import android.view.View;
import android.view.Window;
import android.widget.Button;
import android.widget.Toast;

public class FirstB extends Activity{
    protected void onCreate(Bundle savedInstanceState){
            super.onCreate(savedInstanceState);
            requestWindowFeature(Window.FEATURE_CONTEXT_MENU);
            setContentView(com.sample.test02.R.layout.first_layout);
           Button butt=(Button)findViewById(com.sample.test02.R.id.button_1);
           butt.setOnClickListener(new View.OnClickListener() {

            @Override
            public void onClick(View v) {
                // TODO Auto-generated method stub
                Toast.makeText(FirstB.this,"@+string/bt",Toast.LENGTH_SHORT).show();
            }
        });
        }

报 butt.setOnClickListener(new View.OnClickListener() { 这一行空指针错误

Answer 1

Button butt=(Button)findViewById(com.sample.test02.R.id.button_1);
这里没有找到id叫button_1的按钮