Ndtyjky

Well, I have recyclerView and a fragment as the examples of of Master Detail Flows
now i'm getting my data from json and i'm parsing it in the recyclerView perfectly
the problem is whenever I click on it I get null exception..

public class ItemDetailFragment extends Fragment {

/**

 * The fragment argument representing the item ID that this fragment

 * represents.

 */

public static final String ARG_ITEM_ID = "item_id";



/**

 * The dummy content this fragment is presenting.

 */

private DummyContent.DummyItem mItem;



/**

 * Mandatory empty constructor for the fragment manager to instantiate the

 * fragment (e.g. upon screen orientation changes).

 */

public ItemDetailFragment() {

}



@Override

public void onCreate(Bundle savedInstanceState) {

    super.onCreate(savedInstanceState);



    if (getArguments().containsKey(ARG_ITEM_ID)) {

        // Load the dummy content specified by the fragment

        // arguments. In a real-world scenario, use a Loader

        // to load content from a content provider.

        mItem = DummyContent.ITEM_MAP.get(getArguments().getString(ARG_ITEM_ID));



        Activity activity = this.getActivity();

        CollapsingToolbarLayout appBarLayout = (CollapsingToolbarLayout) activity.findViewById(R.id.toolbar_layout);

        if (appBarLayout != null) {

            appBarLayout.setTitle(mItem.id);

        }

    }

}



@Override

public View onCreateView(LayoutInflater inflater, ViewGroup container,

                         Bundle savedInstanceState) {

    View rootView = inflater.inflate(R.layout.item_detail, container, false);



    // Show the dummy content as text in a TextView.

    if (mItem != null) {

        ((TextView) rootView.findViewById(R.id.item_detail)).setText("hello");





    }



    return rootView;

}

and this is the Activity

public class ItemDetailActivity extends AppCompatActivity {



@Override

protected void onCreate(Bundle savedInstanceState) {

    super.onCreate(savedInstanceState);

    setContentView(R.layout.activity_item_detail);

    Toolbar toolbar = (Toolbar) findViewById(R.id.detail_toolbar);

    setSupportActionBar(toolbar);



    FloatingActionButton fab = (FloatingActionButton) findViewById(R.id.fab);

    fab.setOnClickListener(new View.OnClickListener() {

        @Override

        public void onClick(View view) {

            Snackbar.make(view, "Replace with your own detail action", Snackbar.LENGTH_LONG)

                    .setAction("Action", null).show();

        }

    });



    // Show the Up button in the action bar.

    ActionBar actionBar = getSupportActionBar();

    if (actionBar != null) {

        actionBar.setDisplayHomeAsUpEnabled(true);

    }



    // savedInstanceState is non-null when there is fragment state

    // saved from previous configurations of this activity

    // (e.g. when rotating the screen from portrait to landscape).

    // In this case, the fragment will automatically be re-added

    // to its container so we don't need to manually add it.

    // For more information, see the Fragments API guide at:

    //

    // http://developer.android.com/guide/components/fragments.html

    //

    if (savedInstanceState == null) {

        // Create the detail fragment and add it to the activity

        // using a fragment transaction.

        Bundle arguments = new Bundle();

        arguments.putString(ItemDetailFragment.ARG_ITEM_ID,

                getIntent().getStringExtra(ItemDetailFragment.ARG_ITEM_ID));

        ItemDetailFragment fragment = new ItemDetailFragment();

        fragment.setArguments(arguments);

        getSupportFragmentManager().beginTransaction()

                .add(R.id.item_detail_container, fragment)

                .commit();

    }

}



@Override

public boolean onOptionsItemSelected(MenuItem item) {

    int id = item.getItemId();

    if (id == android.R.id.home) {

        // This ID represents the Home or Up button. In the case of this

        // activity, the Up button is shown. For

        // more details, see the Navigation pattern on Android Design:

        //

        // http://developer.android.com/design/patterns/navigation.html#up-vs-back

        //

        navigateUpTo(new Intent(this, ItemListActivity.class));

        return true;

    }

    return super.onOptionsItemSelected(item);

}

 }

this is where i get the json and ItemlistActivity

public class ItemListActivity extends AppCompatActivity {

View recyclerView;

/**

 * Whether or not the activity is in two-pane mode, i.e. running on a tablet

 * device.

 */

private boolean mTwoPane;

RequestQueue queue;





@Override

protected void onCreate(Bundle savedInstanceState) {

    super.onCreate(savedInstanceState);

    setContentView(R.layout.activity_item_list);

    queue = Volley.newRequestQueue(this);

    Toolbar toolbar = (Toolbar) findViewById(R.id.toolbar);

    setSupportActionBar(toolbar);

    toolbar.setTitle(getTitle());



    FloatingActionButton fab = (FloatingActionButton) findViewById(R.id.fab);

    fab.setOnClickListener(new View.OnClickListener() {

        @Override

        public void onClick(View view) {

            Snackbar.make(view, "Replace with your own action", Snackbar.LENGTH_LONG)

                    .setAction("Action", null).show();

        }

    });



     recyclerView = findViewById(R.id.item_list);

    assert recyclerView != null;



    if (findViewById(R.id.item_detail_container) != null) {

        // The detail container view will be present only in the

        // large-screen layouts (res/values-w900dp).

        // If this view is present, then the

        // activity should be in two-pane mode.

        mTwoPane = true;

    }

    connection();



}



private void setupRecyclerView(@NonNull RecyclerView recyclerView) {

    recyclerView.setAdapter(new SimpleItemRecyclerViewAdapter(DummyContent.ITEMS));

}



public class SimpleItemRecyclerViewAdapter

        extends RecyclerView.Adapter<ViewHolder> {



    private final List<DummyContent.DummyItem> mValues;



    public SimpleItemRecyclerViewAdapter(List<DummyContent.DummyItem> items) {

        mValues = items;

    }



    @Override

    public ViewHolder onCreateViewHolder(ViewGroup parent, int viewType) {

        View view = LayoutInflater.from(parent.getContext())

                .inflate(R.layout.item_list_content, parent, false);

        return new ViewHolder(view);

    }



    @Override

    public void onBindViewHolder(final ViewHolder holder, int position) {



        String profilePicUrl = mValues.get(position).profile_pic;

        String full_name = mValues.get(position).full_name;

        String state = mValues.get(position).state;

        String city = mValues.get(position).city;

        String phoneNo =  mValues.get(position).phone_no;



        holder.full_name.setText("Name : " +full_name);

        holder.state.setText("State : " +state);

        holder.city.setText("City : " +city);

        holder.phone_number.setText("Phone Number : " +phoneNo);

        Glide.with(getApplicationContext())

                .load(profilePicUrl)

                .fitCenter()

                .override(500,500)

                .into(holder.profile_pic);









        holder.mView.setOnClickListener(new View.OnClickListener() {

            @Override

            public void onClick(View v) {

                if (mTwoPane) {

                    Bundle arguments = new Bundle();

                    arguments.putString(ItemDetailFragment.ARG_ITEM_ID, holder.mItem.id);

                    ItemDetailFragment fragment = new ItemDetailFragment();

                    fragment.setArguments(arguments);

                    getSupportFragmentManager().beginTransaction()

                            .replace(R.id.item_detail_container, fragment)

                            .commit();

                } else {

                    Context context = v.getContext();

                    Intent intent = new Intent(context, ItemDetailActivity.class);

                    Log.e("hello",holder.mItem.full_name);

                    intent.putExtra(ItemDetailFragment.ARG_ITEM_ID, holder.mItem.id);



                    context.startActivity(intent);

                }

            }

        });

    }



    @Override

    public int getItemCount() {

        return mValues.size();

    }





}



public void connection(){



    final String url = "aaaaa";



    // prepare the Request

    JsonObjectRequest getRequest = new JsonObjectRequest(Request.Method.GET, url, null,

            new Response.Listener<JSONObject>()

            {

                @Override

                public void onResponse(JSONObject response) {

                    // display response

                    try {

                        JSONArray jsonArray = response.getJSONArray("results");



                        for (int i = 0; i < jsonArray.length(); i++) {



                            JSONObject test = jsonArray.getJSONObject(i);

                            String gender = test.getString("gender");





                            String full_name = test.getJSONObject("name").getString("title") + " " +

                                    test.getJSONObject("name").getString("first") + " " +

                                    test.getJSONObject("name").getString("last");



                            String state = test.getJSONObject("location").getString("state");

                            String city = test.getJSONObject("location").getString("city");

                            String phone_no = test.getString("phone");

                            String profile_pic = test.getJSONObject("picture").getString("large");

                            String id = test.getJSONObject("id").getString("name");

                            Log.d("test2222", gender + " n " + full_name + " n " + state + " n " + city + " n " + phone_no + "n" + profile_pic

                                    + "n" + id);





                            addItem(new DummyContent.DummyItem(gender,profile_pic, full_name, state, city, phone_no,"hello"));

                        }                            



                        setupRecyclerView((RecyclerView) recyclerView);





                    } catch (JSONException e) {

                        e.printStackTrace();

                    }

                }

            },

            new Response.ErrorListener()

            {

                @Override

                public void onErrorResponse(VolleyError error) {

                    Log.d("Error.Response", error.toString());

                    Toast.makeText(getApplicationContext(),"check internet connection",Toast.LENGTH_SHORT).show();



                }

            }

    );



    // add it to the RequestQueue



    queue.add(getRequest);

}

and at last dummycontent

public class DummyContent {



/**

 * An array of sample (dummy) items.

 */

public static final List<DummyItem> ITEMS = new ArrayList<DummyItem>();



/**

 * A map of sample (dummy) items, by ID.

 */

public static final Map<String, DummyItem> ITEM_MAP = new HashMap<String, DummyItem>();



private static final int COUNT = 25;



static {

    // Add some sample items.

}



public static void addItem(DummyItem item) {

    ITEMS.add(item);

    ITEM_MAP.put(item.full_name, item);





}







/**

 * A dummy item representing a piece of content.

 */

public static class DummyItem  {

    public final String id;

    public final String profile_pic;

    public final String full_name;

    public final String state;

    public final String city;

    public final String phone_no;



    public final String data;







    public DummyItem(String id ,String profile_pic, String full_name, String state ,String city,String phone_no,String data) {

        this.id = id;

        this.profile_pic = profile_pic;

        this.full_name = full_name;

        this.state = state;

        this.city = city;

        this.phone_no = phone_no;

        this.data = data;



    }







    @Override

    public String toString() {

        return full_name;

    }

}

 }

now the thing is that I want to get same data (text or image) to the fragment
my problem is that I can't even show the fragment with custom "hello world" textview i get exception whenever I click on the recyclerview so explain to me where is the wrong in my code thanks

and this is the ViewHolder

public class ViewHolder extends RecyclerView.ViewHolder {

public final View mView;

public final ImageView profile_pic;

public final TextView full_name;

public final TextView state;

public final TextView city;

public final TextView phone_number;





public DummyContent.DummyItem mItem;



public ViewHolder(View view) {

    super(view);

    mView = view;

    profile_pic = (ImageView) view.findViewById(R.id.profile_pic);

    full_name = (TextView) view.findViewById(R.id.full_name_txt);

    state = (TextView) view.findViewById(R.id.state_txt);

    city = (TextView) view.findViewById(R.id.city_txt);

    phone_number = (TextView) view.findViewById(R.id.phone_no_txt);





}



@Override

public String toString() {

    return super.toString() + " '" + full_name.getText() + "'";

}

}

You are getting null value because you are using mItem from ViewHolder class without initializing, which is null.

Try this:

 DummyContent.DummyItem mItem = mValues.get(position);  //initialize here, not in ViewHolder class

holder.mView.setOnClickListener(new View.OnClickListener() {

        @Override

        public void onClick(View v) {

            if (mTwoPane) {

                Bundle arguments = new Bundle();

                arguments.putString(ItemDetailFragment.ARG_ITEM_ID, mItem.id); //use without holder

                ItemDetailFragment fragment = new ItemDetailFragment();

                fragment.setArguments(arguments);

                getSupportFragmentManager().beginTransaction()

                        .replace(R.id.item_detail_container, fragment)

                        .commit();

            } else {

                Context context = v.getContext();

                Intent intent = new Intent(context, ItemDetailActivity.class);

                Log.e("hello",holder.mItem.full_name);

                intent.putExtra(ItemDetailFragment.ARG_ITEM_ID, mItem.id); //same here



                context.startActivity(intent);

            }

        }

    });