解決Android中fragment_main.xml文件中的組件獲取的問題

package com.dhy.phonedial;

import android.app.Activity;
import android.app.Fragment;
import android.content.Intent;
import android.net.Uri;
import android.os.Bundle;
import android.view.LayoutInflater;
import android.view.Menu;
import android.view.MenuItem;
import android.view.View;
import android.view.View.OnClickListener;
import android.view.ViewGroup;
import android.widget.Button;
import android.widget.EditText;

public class MainActivity extends Activity {

	@Override
	protected void onCreate(Bundle savedInstanceState) {
		super.onCreate(savedInstanceState);
		setContentView(R.layout.activity_main);

		if (savedInstanceState == null) {
			getFragmentManager().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. 一個占位符片段包含一個簡單的視圖。
	 */
	/**
	 * 這個內部類是最新的開發工具所自動完成的,其功能就是對fragment_main.xml文件進行加載並解析,可以獲取fragment_main.
	 * xml中的已注冊組件.
	 * 
	 * @author Martin
	 * 
	 */
	public static class PlaceholderFragment extends Fragment {

		public PlaceholderFragment() {

		}

		@Override
		public View onCreateView(LayoutInflater inflater, ViewGroup container,
				Bundle savedInstanceState) {
			// 獲取視圖對象根據fragment_main.xml文件
			final View rootView = inflater.inflate(R.layout.fragment_main,
					container, false);

			// 通過視圖對象獲取組件
			Button dialBtn = (Button) rootView.findViewById(R.id.btn_dial);
			System.out.println(rootView.findViewById(R.id.btn_dial)
					+ "============" + R.id.btn_dial + "==================="
					+ dialBtn);

			// 為組件添加事件
			// 由於我也是新手還沒有解決不使用匿名內部類如何獲取組件的問題,
			dialBtn.setOnClickListener(new OnClickListener() {

				@Override
				public void onClick(View v) {
					// TODO Auto-generated method stub
					// 同樣通過視圖對象獲取組件
					EditText et_number = (EditText) rootView
							.findViewById(R.id.edit_number);
					String number = et_number.getText().toString();
					System.out.println("================" + number);
					
					Intent intent = new Intent();
					intent.setAction(Intent.ACTION_CALL);
					intent.setData(Uri.parse("tel:" + number));
					startActivity(intent);
				}

			});

			return rootView;
		}

	}

}