在viewpager中打开新片段时，应用程序崩溃

public class FirstFragment extends Fragment {

	private static final String TAG = "FirstFragment";

	@Override
	public View onCreateView(LayoutInflater inflater, ViewGroup container,
			Bundle savedInstanceState) {
		// Inflate the layout for this fragment
		View view = inflater.inflate(R.layout.first_fragment, container, false);

		Button btn = (Button) view.findViewById(R.id.btn);

		btn.setOnClickListener(new OnClickListener() {

			@Override
			public void onClick(View v) {
				FragmentTransaction trans = getFragmentManager()
						.beginTransaction();
				/*
				 * IMPORTANT: We use the "root frame" defined in
				 * "root_fragment.xml" as the reference to replace fragment
				 */
				trans.replace(R.id.root_frame, new SecondFragment());

				/*
				 * IMPORTANT: The following lines allow us to add the fragment
				 * to the stack and return to it later, by pressing back
				 */
				trans.setTransition(FragmentTransaction.TRANSIT_FRAGMENT_OPEN);
				trans.addToBackStack(null);

				trans.commit();
			}
		});

		return view;
	}

}

First tab:

public class RootFragment extends Fragment {

	private static final String TAG = "RootFragment";

	@Override
	public View onCreateView(LayoutInflater inflater, ViewGroup container,
			Bundle savedInstanceState) {
		/* Inflate the layout for this fragment */
		View view = inflater.inflate(R.layout.root_fragment, container, false);

		FragmentTransaction transaction = getFragmentManager()
				.beginTransaction();
		/*
		 * When this container fragment is created, we fill it with our first
		 * "real" fragment
		 */
		transaction.replace(R.id.root_frame, new FirstFragment());

		transaction.commit();

		return view;
	}

}

Main Activity:

public class MainActivity extends AppCompatActivity {

	// For this example, only two pages
	static final int NUM_ITEMS = 2;
	private TabLayout tabLayout;
	private ViewPager mPager;
	private int[] tabIcons = {
			R.drawable.facebook,
			R.drawable.twitter
	};

	SlidePagerAdapter mPagerAdapter;

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

		/* Instantiate a ViewPager and a PagerAdapter. */
		tabLayout=(TabLayout)findViewById(R.id.tabs);
		mPager = (ViewPager) findViewById(R.id.viewpager);
		mPagerAdapter = new SlidePagerAdapter(getSupportFragmentManager());
		mPager.setAdapter(mPagerAdapter);
		setupTabIcons();

	}

	private void setupTabIcons() {
		tabLayout.getTabAt(0).setIcon(tabIcons[0]);
		tabLayout.getTabAt(1).setIcon(tabIcons[1]);
	}

	/* PagerAdapter class */
	public class SlidePagerAdapter extends FragmentPagerAdapter {
		public SlidePagerAdapter(FragmentManager fm) {
			super(fm);
		}

		@Override
		public Fragment getItem(int position) {
			/*
			 * IMPORTANT: This is the point. We create a RootFragment acting as
			 * a container for other fragments
			 */
			if (position == 0)
				return new RootFragment();
			else
				return new StaticFragment();
		}

		@Override
		public int getCount() {
			return NUM_ITEMS;
		}
	}

}