MainActivity 访问 fragment_main.xml 中的组件 空指针

最近开始学习Android开发，遇到MainActivity 访问 fragment_main.xml 中的组件空指针问题，各种查资料，没找到好的完整解决方法，只好自己写一个，Activity生命周期还没深入理解，可能存在问题，请大家见谅！最近学习感觉就像又开始搞web前台了-_-!

package com.example.translatedatabyintent;import java.util.zip.Inflater;import android.support.v7.app.ActionBarActivity;import android.support.v7.app.ActionBar;import android.support.v4.app.Fragment;import android.text.StaticLayout;import android.app.Activity;import android.content.Context;import android.content.Intent;import android.os.Bundle;import android.view.LayoutInflater;import android.view.Menu;import android.view.MenuItem;import android.view.View;import android.view.ViewGroup;import android.widget.Button;import android.os.Build;public class MainActivity extends ActionBarActivity {private Button button;private static Fragment fragment;@Overrideprotected void onStart(){super.onStart();button = (Button)fragment.getView().findViewById(R.id.button1);//根据id查找到某一视图//绑定事件button.setOnClickListener(new View.OnClickListener() {@Overridepublic void onClick(View v) {// TODO Auto-generated method stub    Intent intent = new Intent(MainActivity.this,OtherActivity.class);    //意图中传递数据    intent.putExtra("name", "张三");    intent.putExtra("age", 23);    intent.putExtra("address", "北京");    //启动意图    startActivity(intent);    }});}@Overrideprotected void onCreate(Bundle savedInstanceState) {super.onCreate(savedInstanceState);setContentView(R.layout.activity_main);//加载布局文件//加载布局if (savedInstanceState == null) {fragment =new PlaceholderFragment();getSupportFragmentManager().beginTransaction().add(R.id.container, fragment).commit();}//View rootView =Inflater.inflate()}@Overridepublic 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;}@Overridepublic 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. *///加载碎片！public static class PlaceholderFragment extends Fragment {public PlaceholderFragment() {}@Overridepublic View onCreateView(LayoutInflater inflater, ViewGroup container,Bundle savedInstanceState) {View rootView = inflater.inflate(R.layout.fragment_main, container,false);return rootView;}}}