How to pass a string between fragments in a viewpager

Question

I'm trying to pass a string between two fragments in a viewpager but I didn't found the right way to do it. Here is my code so far :

public class MyFragmentPagerAdapter extends FragmentPagerAdapter{

    final int PAGE_COUNT = 6;

    /** Constructor of the class */
    public MyFragmentPagerAdapter(FragmentManager fm) {
        super(fm);
    }

    /** This method will be invoked when a page is requested to create */
    @Override
    public Fragment getItem(int arg0) {


        switch (arg0) {
        case 0:
            return new MyFragment();
        case 1:
            return new part2();
        case 2:
            return new Part3();
        case 3:
            return new Part4();
        case 4:
            return new Part5();
        case 5:
            return new Part6();
        default:
            return null;
        }
    }

    /** Returns the number of pages */
    @Override
    public int getCount() {     
        return PAGE_COUNT;
    }

    @Override
    public CharSequence getPageTitle(int position) {        
        return "Page #" + ( position + 1 );
    }





}

public class MainActivity extends FragmentActivity {

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

        /** Getting a reference to the ViewPager defined the layout file */        
        ViewPager pager = (ViewPager) findViewById(R.id.pager);

        /** Getting fragment manager */
        FragmentManager fm = getSupportFragmentManager();

        /** Instantiating FragmentPagerAdapter */
        MyFragmentPagerAdapter pagerAdapter = new MyFragmentPagerAdapter(fm);

        /** Setting the pagerAdapter to the pager object */
        pager.setAdapter(pagerAdapter);

    }

    @Override
    public boolean onCreateOptionsMenu(Menu menu) {
        getMenuInflater().inflate(R.menu.activity_main, menu);
        return true;
    }
}

I'm not using tabs with the viewpager. What should I write in the fragments?

UPDATE : I tried to implement an interface like suggested in the answers :

public interface OnTogglePressListener {
    public void onTogglePressed(String msg);
}

On the first fragment :

@Override
public void onAttach(Activity activity) {
        // TODO Auto-generated method stub
        try {
            buttonListener = (OnTogglePressListener) getActivity();
        } catch (ClassCastException e) {
            throw new ClassCastException(activity.toString() + " must implement onTogglePressed");
        }
        super.onAttach(activity);
    }

@Override
public void onViewCreated(View view, Bundle savedInstanceState) {
        // TODO Auto-generated method stub
        buttonListener.onTogglePressed("Off");
... }

On the second fragment :

public String getEtat(String etat)
    {   state =etat;
        return etat;

    }

On the main activity :

public void onTogglePressed(String etat)
    {
        Part5 p = (Part5)getSupportFragmentManager().findFragmentById(R.layout.frag_2);
        p.getEtat(etat);

    }

But I got a NullPointerException everytime.

Answer 1

You're obviously using ViewPager and you can take advantage of it. You can add a tag to a ViewPager like this:

Activity:

pager.setTag("some text");  // pager is a ViewPager object

Then you can get this data via ViewGroup in a fragment like this:

Fragment:

@Override
public View onCreateView(LayoutInflater inflater, ViewGroup container, Bundle savedInstanceState) {
    View view =  inflater.inflate(R.layout.fragment_main, container, false);

    String result = container.getTag().toString();
    // do something with the result

    return view;

You can also setTag() to the container in the fragment.

This is the cleanest solution I found for sending data among fragments and their mother activity. Another solution (not mentioned here so far) is sending data through SharedPreferences, but I would suggest using tags if possible.

Answer 2

So i found the solution, the implementation is correct, the only thing that I should do the treatement I want in the method on the second fragment and that's it !