my adapter of recycler view returning null

Question

I am trying to use a RecyclerView with an adapter to call a specific person. In the adapter I am using a call button and taking a reference from PlaceCallActivity. The problem is that PlaceCallActivity is using the above values which I can't access from the adapter. Thanks in advance for your help.

My PlaceCallActivity:

package techheromanish.example.com.videochatapp;

import com.sinch.android.rtc.calling.Call;

import android.content.Intent;
import android.os.Bundle;
import android.support.v7.widget.LinearLayoutManager;
import android.support.v7.widget.RecyclerView;
import android.view.View;
import android.view.View.OnClickListener;
import android.widget.Button;
import android.widget.EditText;
import android.widget.TextView;
import android.widget.Toast;

import java.util.ArrayList;
import java.util.List;

public class PlaceCallActivity extends BaseActivity {

    private Button mCallButton;
    private EditText mCallName;

    private RecyclerView recyclerView;
    private RecyclerView.Adapter adapter;
    private List<ListItem> listItems;

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

        //initializing UI elements
        //mCallName = (EditText) findViewById(R.id.callName);
        mCallButton = (Button) findViewById(R.id.callButton);
        //mCallButton.setEnabled(false);
        //mCallButton.setOnClickListener(buttonClickListener);

        Button stopButton = (Button) findViewById(R.id.stopButton);
        stopButton.setOnClickListener(buttonClickListener);

        recyclerView = (RecyclerView) findViewById(R.id.recyclerView);
        recyclerView.setHasFixedSize(true);
        recyclerView.setLayoutManager(new LinearLayoutManager(this));

        listItems = new ArrayList<>();

//        loadRecyclerViewData();

        ListItem listItem = new ListItem(
                R.drawable.user,
                "Jawad",
                "Android Developer");
        listItems.add(listItem);

        ListItem listItem1 = new ListItem(
                R.drawable.user,
                "Malik",
                "Developer");


        listItems.add(listItem1);

        adapter = new MyAdapter(listItems, this);
        recyclerView.setAdapter(adapter);

    }

    // invoked when the connection with SinchServer is established
    @Override
    protected void onServiceConnected() {
        TextView userName = (TextView) findViewById(R.id.loggedInName);
        userName.setText(getSinchServiceInterface().getUserName());
        //mCallButton.setEnabled(true);
    }

    @Override
    public void onDestroy() {
        if (getSinchServiceInterface() != null) {
            getSinchServiceInterface().stopClient();
        }
        super.onDestroy();
    }

    //to kill the current session of SinchService
    private void stopButtonClicked() {
        if (getSinchServiceInterface() != null) {
            getSinchServiceInterface().stopClient();
        }
        finish();
    }

    //to place the call to the entered name
    public void callButtonClicked(String user) {
        //String userName = mCallName.getText().toString();
        if (user.isEmpty()) {
            Toast.makeText(this, "Please enter a user to call", Toast.LENGTH_LONG).show();
            return;
        }

        Call call = getSinchServiceInterface().callUserVideo(user);
        String callId = call.getCallId();
        Intent callScreen = new Intent(this, CallScreenActivity.class);
        callScreen.putExtra(SinchService.CALL_ID, callId);
        startActivity(callScreen);
    }


    private OnClickListener buttonClickListener = new OnClickListener() {
        @Override
        public void onClick(View v) {
            switch (v.getId()) {
                case R.id.callButton:
                    String str = MyAdapter.getStr();
                    Toast.makeText(PlaceCallActivity.this, "" + str, Toast.LENGTH_SHORT).show();
                    //callButtonClicked(str);
                    break;

                case R.id.stopButton:
                    stopButtonClicked();
                    break;
            }
        }
    };
}

and MyAdapter Class:

package techheromanish.example.com.videochatapp;

import android.content.Context;
import android.support.annotation.NonNull;
import android.support.v7.widget.RecyclerView;
import android.view.LayoutInflater;
import android.view.View;
import android.view.ViewGroup;
import android.widget.Button;
import android.widget.ImageView;
import android.widget.LinearLayout;
import android.widget.TextView;
import android.widget.Toast;

import java.util.List;

public class MyAdapter extends RecyclerView.Adapter<MyAdapter.ViewHolder> {

    private List<ListItem> listItems;
    private Context context;
    private static String str;

    public MyAdapter(List<ListItem> listItems, Context context) {
        this.listItems = listItems;
        this.context = context;
    }

    @NonNull
    @Override
    public ViewHolder onCreateViewHolder(@NonNull ViewGroup parent, int viewType) {
        View v = LayoutInflater.from(parent.getContext())
                .inflate(R.layout.list_item_view, parent, false);
        return new ViewHolder(v);
    }

    @Override
    public void onBindViewHolder(@NonNull ViewHolder holder, int position) {
        final ListItem listItem = listItems.get(position);

        holder.imageViewProfile.setImageResource(listItem.getImage());
        holder.textViewName.setText(listItem.getName());
        holder.textViewBio.setText(listItem.getBio());

        /*Picasso.with(context)
                .load(listItem.getImageUrl())
                .into(holder.imageView);
*/
//        str = listItem.getName();

        holder.callButton.setOnClickListener(new View.OnClickListener() {
            @Override
            public void onClick(View v) {
                Toast.makeText(context, "You Clicked " + listItem.getName(), Toast.LENGTH_SHORT).show();
                PlaceCallActivity placeCallActivity = new PlaceCallActivity();
                placeCallActivity.callButtonClicked(listItem.getName());
            }
        });

    }

    @Override
    public int getItemCount() {
        return listItems.size();
    }

    public class ViewHolder extends RecyclerView.ViewHolder {

        public TextView textViewName, textViewBio;
        public ImageView imageViewProfile;
        public Button callButton;

        ViewHolder(View itemView) {
            super(itemView);

            textViewName = (TextView) itemView.findViewById(R.id.textViewName);
            textViewBio = (TextView) itemView.findViewById(R.id.textViewBio);
            imageViewProfile = (ImageView) itemView.findViewById(R.id.imageViewProfile);
            callButton = (Button) itemView.findViewById(R.id.callButton);


        }
    }

    public static String getStr() {
        return str;
    }
}

In this adapter I am using button to call from PlaceCallActivity.

Prashanth Verma · Answer 1 · 2018-09-25T20:54:05.537

1

Please change this:

private RecyclerView.Adapter adapter;

to this:

private MyAdapter adapter;

edited Sep 25 '18 at 20:54

answered Sep 25 '18 at 20:23

Prashanth Verma

588
3
11

java.lang.NullPointerException: Attempt to invoke virtual method 'com.sinch.android.rtc.calling.Call techheromanish.example.com.videochatapp.SinchService$SinchServiceInterface.callUserVideo(java.lang.String)' on a null object reference at techheromanish.example.com.videochatapp.PlaceCallActivity.callButtonClicked(PlaceCallActivity.java:110) – Sep 25 '18 at 20:31
You need to change the way click listener is used. Please look at this link on how to implement a click listener. https://stackoverflow.com/questions/24471109/recyclerview-onclick – Prashanth Verma Sep 25 '18 at 20:56
but i want that button to be clicked – Sep 26 '18 at 20:23

max · Answer 2 · 2018-09-26T21:20:27.033

you can create an interface:

public interface CallButtonClickListener{
    void onButtonClicked(String name);
}

Edit

public class PlaceCallActivity extends BaseActivity {
    private Button mCallButton;
    private EditText mCallName;

    private RecyclerView recyclerView;
    private RecyclerView.Adapter adapter;
    private List<ListItem> listItems;

    //new code
    private CallButtonClickListener buttonListener;

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

        //initializing UI elements
        //mCallName = (EditText) findViewById(R.id.callName);
        mCallButton = (Button) findViewById(R.id.callButton);
        //mCallButton.setEnabled(false);
        //mCallButton.setOnClickListener(buttonClickListener);

        Button stopButton = (Button) findViewById(R.id.stopButton);
        stopButton.setOnClickListener(buttonClickListener);

        recyclerView = (RecyclerView) findViewById(R.id.recyclerView);
        recyclerView.setHasFixedSize(true);
        recyclerView.setLayoutManager(new LinearLayoutManager(this));

        listItems = new ArrayList<>();

//        loadRecyclerViewData();

        ListItem listItem = new ListItem(
                R.drawable.user,
                "Jawad",
                "Android Developer");
        listItems.add(listItem);

        ListItem listItem1 = new ListItem(
                R.drawable.user,
                "Malik",
                "Developer");


        listItems.add(listItem1);

         //implement the logic there
        adapter = new MyAdapter(listItems, this, new CallButtonClickListener(){
         @Override
         public void onButtonClicked(String name){
            //your code here.
         }
       });
        recyclerView.setAdapter(adapter);

    }

    // invoked when the connection with SinchServer is established
    @Override
    protected void onServiceConnected() {
        TextView userName = (TextView) findViewById(R.id.loggedInName);
        userName.setText(getSinchServiceInterface().getUserName());
        //mCallButton.setEnabled(true);
    }

    @Override
    public void onDestroy() {
        if (getSinchServiceInterface() != null) {
            getSinchServiceInterface().stopClient();
        }
        super.onDestroy();
    }

    //to kill the current session of SinchService
    private void stopButtonClicked() {
        if (getSinchServiceInterface() != null) {
            getSinchServiceInterface().stopClient();
        }
        finish();
    }

    //to place the call to the entered name
    public void callButtonClicked(String user) {
        //String userName = mCallName.getText().toString();
        if (user.isEmpty()) {
            Toast.makeText(this, "Please enter a user to call", Toast.LENGTH_LONG).show();
            return;
        }

        Call call = getSinchServiceInterface().callUserVideo(user);
        String callId = call.getCallId();
        Intent callScreen = new Intent(this, CallScreenActivity.class);
        callScreen.putExtra(SinchService.CALL_ID, callId);
        startActivity(callScreen);
    }


    private OnClickListener buttonClickListener = new OnClickListener() {
        @Override
        public void onClick(View v) {
            switch (v.getId()) {
                case R.id.callButton:
                    String str = MyAdapter.getStr();
                    Toast.makeText(PlaceCallActivity.this, "" + str, Toast.LENGTH_SHORT).show();
                    //callButtonClicked(str);
                    break;

                case R.id.stopButton:
                    stopButtonClicked();
                    break;
            }
        }
    };
}

Adapter

public class MyAdapter extends RecyclerView.Adapter<MyAdapter.ViewHolder> {

    private List<ListItem> listItems;
    private Context context;
    private static String str;
    private CallButtonClickListener buttonListener;

    public MyAdapter(List<ListItem> listItems, Context context, CallButtonClickListener buttonListener) {
        this.listItems = listItems;
        this.context = context;
        this.buttonListener = buttonListner;
    }

    @NonNull
    @Override
    public ViewHolder onCreateViewHolder(@NonNull ViewGroup parent, int viewType) {
        View v = LayoutInflater.from(parent.getContext())
                .inflate(R.layout.list_item_view, parent, false);
        return new ViewHolder(v);
    }

    @Override
    public void onBindViewHolder(@NonNull ViewHolder holder, int position) {
        final ListItem listItem = listItems.get(position);

        holder.imageViewProfile.setImageResource(listItem.getImage());
        holder.textViewName.setText(listItem.getName());
        holder.textViewBio.setText(listItem.getBio());

        /*Picasso.with(context)
                .load(listItem.getImageUrl())
                .into(holder.imageView);
*/
//        str = listItem.getName();

        holder.callButton.setOnClickListener(new View.OnClickListener() {
            @Override
            public void onClick(View v) {
                Toast.makeText(context, "You Clicked " + listItem.getName(), Toast.LENGTH_SHORT).show();


            buttonListener.onButtonClicked(listItem.getName());

            }
        });

    }

    @Override
    public int getItemCount() {
        return listItems.size();
    }

    public class ViewHolder extends RecyclerView.ViewHolder {

        public TextView textViewName, textViewBio;
        public ImageView imageViewProfile;
        public Button callButton;

        ViewHolder(View itemView) {
            super(itemView);

            textViewName = (TextView) itemView.findViewById(R.id.textViewName);
            textViewBio = (TextView) itemView.findViewById(R.id.textViewBio);
            imageViewProfile = (ImageView) itemView.findViewById(R.id.imageViewProfile);
            callButton = (Button) itemView.findViewById(R.id.callButton);


        }
    }

    public static String getStr() {
        return str;
    }
}

i ve tried to implement this but still get exception. would you please implement this in code and paste it here? — , Sep 26 '18 at 20:50
java.lang.NullPointerException: Attempt to invoke interface method 'void techheromanish.example.com.videochatapp.PlaceCallActivity$CallButtonClickListener.onButtonClicked(java.lang.String)' on a null object reference — , Sep 26 '18 at 20:54
on this one buttonListener.onButtonClicked(listItem.getName()); — , Sep 26 '18 at 20:54

kamyar haqqani · Accepted Answer · 2018-09-26T00:24:11.603

creating an instance of an activity wouldn't make it go through its lifecycle; if the declaration of the properties which are necessary to make the code run is dependent on your activity's lifecycle then calling the method on the properly initialized activity instance should solve this.

MyAdapter class:

public class MyAdapter extends RecyclerView.Adapter<MyAdapter.ViewHolder> {

    private List<ListItem> listItems;
    private Context context;
    private PlaceCallActivity placeCallActivity;
    private static String str;

    public MyAdapter(List<ListItem> listItems, Context context) {
        this.listItems = listItems;
        this.context = context;
        // this.placeCallActivity now references the parent activity instance
        this.placeCallActivity=(PlaceCallActivity)context;
    }

    @NonNull
    @Override
    public ViewHolder onCreateViewHolder(@NonNull ViewGroup parent, int viewType) {
        View v = LayoutInflater.from(parent.getContext())
                .inflate(R.layout.list_item_view, parent, false);
        return new ViewHolder(v);
    }

    @Override
    public void onBindViewHolder(@NonNull ViewHolder holder, int position) {
        final ListItem listItem = listItems.get(position);

        holder.imageViewProfile.setImageResource(listItem.getImage());
        holder.textViewName.setText(listItem.getName());
        holder.textViewBio.setText(listItem.getBio());

        /*Picasso.with(context)
                .load(listItem.getImageUrl())
                .into(holder.imageView);
*/
//        str = listItem.getName();

        holder.callButton.setOnClickListener(new View.OnClickListener() {
            @Override
            public void onClick(View v) {
                Toast.makeText(context, "You Clicked " + listItem.getName(), Toast.LENGTH_SHORT).show();
                placeCallActivity.callButtonClicked(listItem.getName());
            }
        });

    }

    @Override
    public int getItemCount() {
        return listItems.size();
    }

    public class ViewHolder extends RecyclerView.ViewHolder {

        public TextView textViewName, textViewBio;
        public ImageView imageViewProfile;
        public Button callButton;

        ViewHolder(View itemView) {
            super(itemView);

            textViewName = (TextView) itemView.findViewById(R.id.textViewName);
            textViewBio = (TextView) itemView.findViewById(R.id.textViewBio);
            imageViewProfile = (ImageView) itemView.findViewById(R.id.imageViewProfile);
            callButton = (Button) itemView.findViewById(R.id.callButton);


        }
    }

    public static String getStr() {
        return str;
    }
}

in holder.callButton.setOnClickListener – kamyar haqqani Sep 26 '18 at 21:18 — kamyar haqqani, Sep 26 '18 at 21:18

my adapter of recycler view returning null

3 Answers3