Android Fragment是Android4.0以上才有的；而FragmentActivity是为了兼容4.0以下版本的Fragment使用的。

所以如果你想兼容4.0以下Android版本使用Fragment的话，框架Activity需要继承FragmentActivity，FragmentActivity这个类是在android.support.v4.app.FragmentActivity里的。

下面介绍2种用法：

1、继承Activity的。

（这个只针对4.0以上的Android平台使用Fragment）。

框架Activity：

package com.tandong.fragment;

import android.app.Activity;
import android.app.Fragment;
import android.app.FragmentManager;
import android.app.FragmentTransaction;
import android.os.Bundle;
import android.view.View;
import android.view.View.OnClickListener;
import android.widget.Button;

/**
 * 不兼容4.0以下模式Fragment
 * 
 * @author tandong
 * 
 */

public class Mt_Activity extends Activity implements OnClickListener {
	private Button btn_first, btn_second;
	private Fragment Fragment_first, Fragment_Second;
	private FragmentTransaction fragmentTransaction;
	private FragmentManager fragmentManager;

	@Override
	protected void onCreate(Bundle savedInstanceState) {
		// TODO Auto-generated method stub
		super.onCreate(savedInstanceState);
		setContentView(R.layout.fragment);
		initView();

		Fragment_Second = new Fragment_Second();
		fragmentManager = this.getFragmentManager();
		fragmentTransaction = fragmentManager.beginTransaction();
		fragmentTransaction.replace(R.id.main_fragment_layout, Fragment_Second,"second_Fragment").commit();
	}

	private void initView() {
		btn_first = (Button) this.findViewById(R.id.btn_first);
		btn_second = (Button) this.findViewById(R.id.btn_second);
		btn_first.setOnClickListener(this);
		btn_second.setOnClickListener(this);
	}

	@Override
	public void onClick(View arg0) {
		switch (arg0.getId()) {
		case R.id.btn_first:
			// 加载不同的Fragment
			if (null == Fragment_first) {
				Fragment_first = new Fragment_first();
			}
			fragmentTransaction = fragmentManager.beginTransaction();
			fragmentTransaction.replace(R.id.main_fragment_layout, Fragment_first, "fist_Fragment");
			fragmentTransaction.commit();
			break;
		case R.id.btn_second:
			if (null == Fragment_first) {
				Fragment_Second = new Fragment_Second();
			}
			fragmentTransaction = fragmentManager.beginTransaction();
			fragmentTransaction.replace(R.id.main_fragment_layout, Fragment_Second, "second_Fragment");
			fragmentTransaction.commit();
			break;
		default:
			break;
		}

	}

}

Fragment代码：

package com.tandong.fragment;

import android.app.Fragment;
import android.os.Bundle;
import android.view.LayoutInflater;
import android.view.View;
import android.view.ViewGroup;

public class Fragment_Second extends Fragment {
      private View rootView;
	@Override
	public View onCreateView(LayoutInflater inflater, ViewGroup container, Bundle savedInstanceState) {
		// TODO Auto-generated method stub
if(container==null)
return null;
		rootView=inflater.inflate(R.layout.fragment_two, container,false);
		
		return rootView;
	}

}

2.继承FragmentActivity的（向下兼容4.0以下版本使用Fragment，导入的是android.support.v4包里的内容）

框架Activity：

package com.tandong.fragment;

import android.os.Bundle;
import android.support.v4.app.Fragment;
import android.support.v4.app.FragmentActivity;
import android.support.v4.app.FragmentManager;
import android.support.v4.app.FragmentTransaction;
import android.view.View;
import android.view.View.OnClickListener;
import android.widget.Button;

/**
 * 兼容4.0以下模式Fragment
 * 
 * @author tandong
 * 
 */

public class Mt_Activity extends FragmentActivity implements OnClickListener {
	private Button btn_first, btn_second;
	private Fragment Fragment_first, Fragment_Second;
	private FragmentTransaction fragmentTransaction;
	private FragmentManager fragmentManager;

	@Override
	protected void onCreate(Bundle savedInstanceState) {
		// TODO Auto-generated method stub
		super.onCreate(savedInstanceState);
		setContentView(R.layout.fragment);
		initView();

		Fragment_first = new Fragment_first();
		fragmentManager = this.getSupportFragmentManager();
		fragmentTransaction = fragmentManager.beginTransaction();
		fragmentTransaction.replace(R.id.main_fragment_layout, Fragment_first,"first_Fragment").commit();
	}

	private void initView() {
		btn_first = (Button) this.findViewById(R.id.btn_first);
		btn_second = (Button) this.findViewById(R.id.btn_second);
		btn_first.setOnClickListener(this);
		btn_second.setOnClickListener(this);
	}

	@Override
	public void onClick(View arg0) {
		switch (arg0.getId()) {
		case R.id.btn_first:
			// 加载不同的Fragment
			if (null == Fragment_first) {
				Fragment_first = new Fragment_first();
			}
			fragmentTransaction = fragmentManager.beginTransaction();
			fragmentTransaction.replace(R.id.main_fragment_layout, Fragment_first, "fist_Fragment");
			fragmentTransaction.commit();
			break;
		case R.id.btn_second:
			if (null == Fragment_first) {
				Fragment_Second = new Fragment_Second();
			}
			fragmentTransaction = fragmentManager.beginTransaction();
			fragmentTransaction.replace(R.id.main_fragment_layout, Fragment_Second, "second_Fragment");
			fragmentTransaction.commit();
			break;
		default:
			break;
		}

	}

}

package com.tandong.fragment;

import android.os.Bundle;
import android.support.v4.app.Fragment;
import android.view.LayoutInflater;
import android.view.View;
import android.view.ViewGroup;

public class Fragment_first extends Fragment {
	private View rootView;

	@Override
	public View onCreateView(LayoutInflater inflater, ViewGroup container, Bundle savedInstanceState) {
if(container==null)
   return null;
		rootView = inflater.inflate(R.layout.fragment_first, container,false);

		return rootView;
	}
}

原著：http://www.aplesson.com/?p=377

Android Fragment和FragmentActivity用法,布布扣,bubuko.com

Android Fragment和FragmentActivity用法