viewpager+fragment滑动切换

import android.app.Activity;
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.FragmentPagerAdapter;
import android.support.v4.view.ViewPager;
import android.support.v4.view.ViewPager.OnPageChangeListener;
import android.view.Menu;
import android.view.MenuItem;
import android.view.View;
import android.widget.RadioButton;
import android.widget.RadioGroup;
import android.widget.RadioGroup.OnCheckedChangeListener;

public class MainActivity extends FragmentActivity {

	private ViewPager vp;
	private RadioGroup rg;

	@Override
	protected void onCreate(Bundle savedInstanceState) {
		super.onCreate(savedInstanceState);
		setContentView(R.layout.activity_main);
		vp = (ViewPager) findViewById(R.id.vp);
		rg = (RadioGroup) findViewById(R.id.rg);
		FragmentManager manager = getSupportFragmentManager();
		vp.setAdapter(new MyPageAdapter(manager));
		rg.setOnCheckedChangeListener(new OnCheckedChangeListener() {
			
			@Override
			public void onCheckedChanged(RadioGroup group, int checkedId) {
				int i=0;
				switch (checkedId) {
				case R.id.rb1:
					i=0;
					break;
				case R.id.rb2:
					i=1;
					break;
				case R.id.rb3:
					i=2;
					break;

				default:
					break;
				}
				vp.setCurrentItem(i);
			}
		});
		vp.setOnPageChangeListener(new OnPageChangeListener() {
			
			@Override
			public void onPageSelected(int arg0) {
				switch (arg0) {
				case 0:
					RadioButton rb1 = (RadioButton) findViewById(R.id.rb1);
					rb1.setChecked(true);
					break;
				case 1:
					RadioButton rb2 = (RadioButton) findViewById(R.id.rb2);
					rb2.setChecked(true);
					break;
				case 2:
					RadioButton rb3 = (RadioButton) findViewById(R.id.rb3);
					rb3.setChecked(true);
					break;

				default:
					break;
				}
				
			}
			
			@Override
			public void onPageScrolled(int arg0, float arg1, int arg2) {
				// TODO Auto-generated method stub
				
			}
			
			@Override
			public void onPageScrollStateChanged(int arg0) {
				// TODO Auto-generated method stub
				
			}
		});
	}

	class MyPageAdapter extends FragmentPagerAdapter{

		public MyPageAdapter(FragmentManager fm) {
			super(fm);
			// TODO Auto-generated constructor stub
		}

		@Override
		public Fragment getItem(int arg0) {
			switch (arg0) {
			case 0:
				Frag1 frag1=new Frag1();
				return frag1;
			case 1:
				Frag2 frag2=new Frag2();
				return frag2;
			case 2:
				Frag3 frag3=new Frag3();
				return frag3;

			default:
				break;
			}
			return null;
		}

		@Override
		public int getCount() {
			// TODO Auto-generated method stub
			return 3;
		}
		
	}
}

XML文件