Here I will explain how we can communicate between two fragments in an Activity. There are many situations where we have to communicate two fragments like we have to pass data between fragments in some events. Here I will communicate through Interface but we need to create an Interface first.

ActivityInterface.java

Create an interface which will help us to communicate.

interface Activityinterface { 
  public void passInfo(); 
} 

Now our Activity ScreenActivity implements ActivityInterface

public class ScreenActivity extends FragmentActivity implements ActivityInterface
@Override 
protected void onCreate(Bundle savedInstanceState) { 
    super.onCreate(savedInstanceState); 
    setContentView(R.layout.activity_screen); 
} 

@Override 
public void passInfo () { 
    // TODO Auto-generated method stub 


// We can call this from Fragment by using ActivityInterface reference. 

FragmentManager fragmentManager = getSupportFragmentManager(); 
SecondFragment secondFragment = (SecondFragment) 
fragmentManager.findFragmentById(R.id.second_fragment); 
secondFragment.changesOccur(); 


} 


} 

public class FirstFragment extends Fragment implements OnClickListener{ 
 Button changeButton; 
 ActivityInterface activityInterface; 
    @Override 
    public View onCreateView(LayoutInflater inflater, ViewGroup container, 

            Bundle savedInstanceState) { 
        // TODO Auto-generated method stub 


    return inflater.inflate(R.layout.layout_fragmenta, container, false); 
} 



@Override 
public void onActivityCreated(Bundle savedInstanceState) { 
    // TODO Auto-generated method stub 


super.onActivityCreated(savedInstanceState); 
        activityInterface = (activityInterface) getActivity(); 
        changeButton = (Button) getActivity().findViewById(R.id.change_button); 
        changeButton.setOnClickListener(this); 
    } 

@Override 
public void onClick(View v) { 
    // TODO Auto-generated method stub 

activityInterface. passInfo (); 


} 
}

public class SecondFragment extends Fragment{ 
int valueCountng; 
TextView countAmount; 
    @Override 
    public View onCreateView(LayoutInflater inflater, ViewGroup container, 

            Bundle savedInstanceState) { 
        // TODO Auto-generated method stub 

  return inflater.inflate(R.layout.second_fragment, container, false); 
} 

@Override 
public void onActivityCreated(Bundle savedInstanceState) { 
    // TODO Auto-generated method stub 
    super.onActivityCreated(savedInstanceState); 
    countAmount = (TextView)getActivity().findViewById(R.id.count_amount); 

} 

public void changesOccur (){ 
    String str = countAmount.getText().toString(); 
    valueCountng = Integer.parseInt(str); 
    valueCountng ++; 
    countAmount.setText(String.valueOf(valueCountng)); 
} 
}