Passing data beetwen fragments in viewpager

Question

I've Viewpager wit 2 fragments: CurrentWeatherFragment and ForecastFragment. I need to pass string from one to another, Iam using interface like below, but I keep getting NullPointerException, the message is not passing propertly...

public class CurrentWeatherFragment extends Fragment {

SendMessage SM

public void onCreateView(...) {
String Message = "Hello"
SM.sendData(Message);
}

interface SendMessage
{
    public  void sendData(String message);
}

@Override
public void onAttach(Activity activity) {
    super.onAttach(activity);

    try {
        SM = (SendMessage) activity;
    } catch(ClassCastException e) {
        throw  new ClassCastException("Musisz zaimplementowac metode sendData");
    }
}
}

MainActivity.java

import android.support.v4.app.FragmentActivity;
import android.support.v4.view.ViewPager;
import android.os.Bundle;


public class MainActivity extends FragmentActivity implements CurrentWeatherFragment.SendMessage {

ViewPager viewPager;


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

    //setting fragment view pager
    viewPager = (ViewPager)findViewById(R.id.pager);
    PagerAdapter pagerAdapter = new PagerAdapter(getSupportFragmentManager());
    viewPager.setAdapter(pagerAdapter);
}

public void sendData (String message){
    ForecastFragment FF = new ForecastFragment();
    FF.getData(message);
}

}

ForecastFragment.java

public class ForecastFragment extends Fragment {

public View onCreateView(){
TextView txt = (TextView)v.findViewById(R.id.txt_forecast);
}

public void getData(String message){
        txt.setText(message);
}
}

I've used this method succesfully in other app where I've had 2 fragments in one activity and i could call them by ID

public void sendData(String message) {

    SecondFragment f2 = (SecondFragment)getFragmentManager().findFragmentById(R.id.F2);
    f2.getData(message);
}

But here Fragments dont have IDs and I think that message is not passed because i dont use FragmentManager(), but how to find fragment in viewpager without ID, any suggestion/ideas?

score 5 · Accepted Answer · answered Apr 19 '15 at 14:30

Although a little hacky what you can do is get the fragment by its tag by using the following code:

String tag = "android:switcher:" + R.id.pager + ":" + index;
Fragment f = getSupportFragmentManager().findFragmentByTag(tag);

Where R.id.pager is the id of the viewpager in your layout and index is the position (as an integer) in the Viewpager Adapter. I can't say this will work forever but it works for me at the moment.

The Alternative i would suggest is using a LocalBroadcastManager and a BroadcastReciver to send data internally between your fragments as although its a little more work it helps get rid of the spaghetti code situation you may end up finding yourself in trying to reference the fragments directly.

score 2 · Answer 2 · answered Apr 19 '15 at 14:30

2

To pass data between fragments you need to pass the data in the object constructor.

Be aware to don't override the default constructor, instead create a static method getInstance(String data).

public static YourClass getInstance(String data) 
{
    YourClass object = new YourClass();
    Bundle bundle =  new Bundle();
    bundle.putString(key, data);
    object.setArguments(bundle);  

    return object;
}

Then you can get the data in the fragment's onCreate method with getArguments()

answered Apr 19 '15 at 14:30

Stefano Vuerich

996
1
7
28

1

This is the proper way of doing it! – Skynet Nov 27 '15 at 07:43
1

This does not answer the question. – rafa Jul 08 '17 at 06:29

score 1 · Answer 3 · answered Apr 26 '17 at 09:35

For some other users like me who looking for fragment to viewpager data sending

Here is working solution :

Sending data from fragment TO tab layout's view pager's fragments:

In Main fragment :

For tab layout i am using two fragments

1) BillDetailFragment and

2) ClientDepMonFragment

private TabLayout tabLayout;
    private ViewPager viewPager;


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


// adding  fragment and passing data to it
        BillDetailFragment billDetailFragment=new BillDetailFragment();
        Bundle bundle=new Bundle();
        bundle.putString("mobile",mobile);
        bundle.putInt("c_id",client_id);
        bundle.putInt("server_id",server_id);
        billDetailFragment.setArguments(bundle);

        ClientDepMonFragment clientDepMonFragment=new ClientDepMonFragment();
        Bundle bundle1=new Bundle();
        bundle1.putString("mobile",mobile);
        bundle1.putInt("c_id",client_id);
        bundle1.putInt("server_id",server_id);
        clientDepMonFragment.setArguments(bundle1);


        tabLayout=(TabLayout)view.findViewById(R.id.detail_txn_tab_layout);
        viewPager=(ViewPager)view.findViewById(R.id.detail_txn_viewpager);
        dtViewPagerAdapter=new DtViewPagerAdapter(getChildFragmentManager(),DetailFragment.this);

        dtViewPagerAdapter.addFragments(billDetailFragment,"Lending Money");
        dtViewPagerAdapter.addFragments(clientDepMonFragment,"Deposited Money");
        viewPager.setAdapter(dtViewPagerAdapter);
        tabLayout.setupWithViewPager(viewPager);
}

and here is how to access that data from fragment

BillDetailFragment: override onCreate method

        private int client_id,server_id;
        private String client_mobile;
        @Override
        public void onCreate(@Nullable Bundle savedInstanceState) 
        {
            super.onCreate(savedInstanceState);
            client_mobile=getArguments().getString("mobile");
            client_id=getArguments().getInt("c_id");
            server_id=getArguments().getInt("server_id");
        }

Passing data beetwen fragments in viewpager

3 Answers3

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