fragment interce instanziieren

public interface ActivityCommunicator {


	public void passDataToActivity(String someValue);
	
}


public interface FragmentCommunicator {
	
	public void passDataToFragment(String someValue);


}

public class MainActivity extends FragmentActivity implements ActivityCommunicator {


	public FragmentCommunicator fragmentCommunicator;
	public int someIntValue = 1;
	SectionsPagerAdapter mSectionsPagerAdapter;
	Button btn;
	ViewPager mViewPager;


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


		btn = (Button)findViewById(R.id.button1);
		mSectionsPagerAdapter = new SectionsPagerAdapter(getSupportFragmentManager());


		// Set up the ViewPager with the sections adapter.
		mViewPager = (ViewPager) findViewById(R.id.pager);
		mViewPager.setAdapter(mSectionsPagerAdapter);
	}


	public void SendText(View v) {
                          	
		if(fragmentCommunicator == null) {
			
			fragmentCommunicator.passDataToFragment("Hi from FragmentActivity");
		}
	}


	@Override
	public void passDataToActivity(String someValue) {
		// TODO Auto-generated method stub
	}
}

public class Fragment1 extends Fragment {
	
	Button btn;
	
	public Fragment1(int position) {
		// TODO Auto-generated constructor stub
	}


	@Override
	public View onCreateView(LayoutInflater inflater, ViewGroup container, Bundle savedInstanceState) {
		
		View v = inflater.inflate(R.layout.fragmen1, container, false);
		btn = (Button)v.findViewById(R.id.button1);
		return v;
	}
}

public class Fragment2 extends Fragment implements FragmentCommunicator {


	public Context context;
	TextView tv;
	private ActivityCommunicator activityCommunicator;
	private String activityAssignedValue ="";
	
	public Fragment2(int position) {
		// TODO Auto-generated constructor stub
	}


	@Override
	public View onCreateView(LayoutInflater inflater, ViewGroup container, Bundle savedInstanceState) {
		
		View v = inflater.inflate(R.layout.fragment2, container, false);
		tv = (TextView)v.findViewById(R.id.textView1);
		return v;
	}
	
	 @Override
	  public void onResume(){
	 	super.onResume();
	 	int activityValue =((MainActivity)context).someIntValue;
	 	if(activityValue == 0){
	    	//show one view
	 	}else{
	   	// show other view
		} 
	 }
	 
	 @Override
 	public void onAttach(Activity activity){
   	super.onAttach(activity);
   	context = getActivity();
   	activityCommunicator =(ActivityCommunicator)context;
 	}


	@Override
	public void passDataToFragment(String someValue) {
		activityAssignedValue = someValue;
		tv.setText(someValue); 
	}
}

<LinearLayout xmlns:android="http://schemas.android.com/apk/res/android"
	android:layout_width="match_parent"
	android:layout_height="match_parent"
	android:orientation="vertical" >


	<Button
    	android:id="@+id/button1"
    	android:layout_width="wrap_content"
    	android:layout_height="wrap_content"
    	android:onClick="SendText"
    	android:text="Button" />


</LinearLayout>

<LinearLayout xmlns:android="http://schemas.android.com/apk/res/android"
	android:layout_width="match_parent"
	android:layout_height="match_parent"
	android:orientation="vertical" >


	<TextView
    	android:id="@+id/textView1"
    	android:layout_width="wrap_content"
    	android:layout_height="wrap_content"
    	android:text="Large Text"
    	android:textAppearance="?android:attr/textAppearanceLarge" />


</LinearLayout>

<android.support.v4.view.ViewPager xmlns:android="http://schemas.android.com/apk/res/android"
	xmlns:tools="http://schemas.android.com/tools"
	android:id="@+id/pager"
	android:layout_width="match_parent"
	android:layout_height="match_parent"
	tools:context=".MainActivity" >


	<!--
	This title strip will display the currently visible page title, as well as the page
	titles for adjacent pages.
	-->


	<android.support.v4.view.PagerTitleStrip
    	android:id="@+id/pager_title_strip"
    	android:layout_width="match_parent"
    	android:layout_height="wrap_content"
    	android:layout_gravity="top"
    	android:background="#33b5e5"
    	android:paddingBottom="4dp"
    	android:paddingTop="4dp"
    	android:textColor="#fff" />


</android.support.v4.view.ViewPager>

public class SectionsPagerAdapter extends FragmentPagerAdapter {
	
	public SectionsPagerAdapter(FragmentManager fm) {
		super(fm);
	}


	@Override
	public Fragment getItem(int position) {


		if(position == 0) {
			Fragment1 f = new Fragment1(position);
			return f;
		}
		else {
			Fragment2 f = new Fragment2(position);
			return f;
		}
	}


	@Override
	public int getCount() {
		// Show 3 total pages.
		return 2;
	}


	@Override
	public CharSequence getPageTitle(int position) {
		switch (position) {
		case 0:
			return "Bla";
		case 1:
			return "Bla";
		}
		return null;
	}
}