Can't get the count of the list item getting NullPointerException

Question

I am getting the error NullPointerException i already try the method mention

Count Total Number of List Items in a ListView

but no luck i want to get the items in list

This is what i am doing

    int count = listView.getAdapter().getCount();

Custom Adapter code

package com.example.wildstone.cv_maker;

import android.content.Context;
import android.support.annotation.NonNull;
import android.support.annotation.Nullable;
import android.view.LayoutInflater;
import android.view.View;
import android.view.ViewGroup;
import android.widget.ArrayAdapter;
import android.widget.ImageView;
import android.widget.TextView;

import java.util.ArrayList;

/**
 * Created by wildstone on 08/02/2018.
 */

public class Custom_Adapter_for_Language extends ArrayAdapter<Language_data_comes_here>
{
    Context context ;;

    public Custom_Adapter_for_Language(Context context, ArrayList<Language_data_comes_here> array) {
        super(context,0 , array);

    }


    @NonNull
    @Override
    public View getView(int position, @Nullable View convertView, @NonNull ViewGroup parent) {


        View v = convertView ;

        if (v == null){

            v = LayoutInflater.from(getContext()).inflate(R.layout.custom_list_view ,parent ,false);


        }

        Language_data_comes_here language_data_comes_here = getItem(position);


        ImageView imageView = (ImageView) v.findViewById(R.id.custom_image_display_list_item);
        TextView textView = (TextView) v.findViewById(R.id.custom_text_display_list_item);

        textView.setText(language_data_comes_here.getLanguage());
        imageView.setImageResource(R.mipmap.language);



return v ;
    }
}

activity main

package com.example.wildstone.cv_maker;

import android.graphics.Color;
import android.support.design.widget.FloatingActionButton;
import android.support.v7.app.AlertDialog;
import android.support.v7.app.AppCompatActivity;
import android.os.Bundle;
import android.support.v7.widget.Toolbar;
import android.view.LayoutInflater;
import android.view.View;
import android.widget.AdapterView;
import android.widget.Button;
import android.widget.EditText;
import android.widget.ListView;
import android.widget.Toast;

import java.util.ArrayList;

public class Language_Activity extends AppCompatActivity {


    ListView listView ;
    FloatingActionButton floatingActionButton ;
   Custom_Adapter_for_Language arrayAdapter ;
    ArrayList<Language_data_comes_here> arr ;
    Toolbar toolbar ;

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



        floatingActionButton = (FloatingActionButton) findViewById(R.id.floating_action_button);
        floatingActionButton.setImageResource(R.mipmap.plus);
        floatingActionButton.setBackgroundColor(Color.WHITE);

        listView = (ListView) findViewById(R.id.list_view);
        arr = new ArrayList<>();
        floatingActionButton.setOnClickListener(new View.OnClickListener() {
            @Override
            public void onClick(View v) {

                final AlertDialog.Builder builder = new AlertDialog.Builder(Language_Activity.this);
                LayoutInflater layoutInflater = getLayoutInflater() ;

                View view  = layoutInflater.inflate(R.layout.enter_language , null);
                final EditText language = (EditText) view.findViewById(R.id.language_entered);

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

                toolbar.setTitle("  Add Language !");
                toolbar.setTitleTextColor(Color.WHITE);
toolbar.setLogo(R.mipmap.language);

                Button add_language = (Button) view.findViewById(R.id.enter_language);


                add_language.setOnClickListener(new View.OnClickListener() {
                    @Override
                    public void onClick(View v) {

                        arr.add(new Language_data_comes_here( R.mipmap.language , language.getText().toString()));

                        arrayAdapter = new Custom_Adapter_for_Language(Language_Activity.this , arr);

                        listView.setAdapter(arrayAdapter);

                        builder.setCancelable(true);
                        language.setText("");

                    }
                });



                builder.setCancelable(true);
                builder.setView(view);

                AlertDialog alertDialog = builder.create() ;
                alertDialog.show();





            }
        });




        listView.setOnItemLongClickListener(new AdapterView.OnItemLongClickListener() {
            @Override
            public boolean onItemLongClick(AdapterView<?> parent, View view, int position, long id) {

                arr.remove(position);
                arrayAdapter.notifyDataSetChanged();
                return false;
            }
        }) ;



getListCount();





    }


    public void getListCount () {

        int count = listView.getAdapter().getCount();
        Button bb = (Button) findViewById(R.id.b);

        switch(count){

            case 1 :
                bb.setOnClickListener(new View.OnClickListener() {
                    @Override
                    public void onClick(View v) {
                        Toast.makeText(Language_Activity.this, "There is 1 item", Toast.LENGTH_SHORT).show();
                    }
                });

                break ;
            case 2 :
                bb.setOnClickListener(new View.OnClickListener() {
                    @Override
                    public void onClick(View v) {
                        Toast.makeText(Language_Activity.this, "There is 2 items", Toast.LENGTH_SHORT).show();
                    }
                });


                break ;
            case 3 :
                bb.setOnClickListener(new View.OnClickListener() {
                    @Override
                    public void onClick(View v) {
                        Toast.makeText(Language_Activity.this, "There is 3 items", Toast.LENGTH_SHORT).show();
                    }
                });

            case 4 :
                bb.setOnClickListener(new View.OnClickListener() {
                    @Override
                    public void onClick(View v) {
                        Toast.makeText(Language_Activity.this, "There is 4 items", Toast.LENGTH_SHORT).show();
                    }
                });

                break ;
            case 5 :
                bb.setOnClickListener(new View.OnClickListener() {
                    @Override
                    public void onClick(View v) {
                        Toast.makeText(Language_Activity.this, "There is 5 items", Toast.LENGTH_SHORT).show();
                    }
                });


                break ;
            case 6 :
                bb.setOnClickListener(new View.OnClickListener() {
                    @Override
                    public void onClick(View v) {
                        Toast.makeText(Language_Activity.this, "There is 6 items", Toast.LENGTH_SHORT).show();
                    }
                });


                break ;
            default:
                Toast.makeText(Language_Activity.this, "There list is empty", Toast.LENGTH_SHORT).show();
                break ;
        }



    }
}

logcat

02-14 22:03:13.736 25664-25664/com.example.wildstone.cv_maker D/AndroidRuntime: Shutting down VM
02-14 22:03:13.739 25664-25664/com.example.wildstone.cv_maker E/AndroidRuntime: FATAL EXCEPTION: main
                                                                                Process: com.example.wildstone.cv_maker, PID: 25664
                                                                                java.lang.RuntimeException: Unable to start activity ComponentInfo{com.example.wildstone.cv_maker/com.example.wildstone.cv_maker.Language_Activity}: java.lang.NullPointerException: Attempt to invoke virtual method 'int com.example.wildstone.cv_maker.Custom_Adapter_for_Language.getCount()' on a null object reference
                                                                                    at android.app.ActivityThread.performLaunchActivity(ActivityThread.java:2984)
                                                                                    at android.app.ActivityThread.handleLaunchActivity(ActivityThread.java:3045)
                                                                                    at android.app.ActivityThread.-wrap14(ActivityThread.java)
                                                                                    at android.app.ActivityThread$H.handleMessage(ActivityThread.java:1642)
                                                                                    at android.os.Handler.dispatchMessage(Handler.java:102)
                                                                                    at android.os.Looper.loop(Looper.java:154)
                                                                                    at android.app.ActivityThread.main(ActivityThread.java:6776)
                                                                                    at java.lang.reflect.Method.invoke(Native Method)
                                                                                    at com.android.internal.os.ZygoteInit$MethodAndArgsCaller.run(ZygoteInit.java:1496)
                                                                                    at com.android.internal.os.ZygoteInit.main(ZygoteInit.java:1386)
                                                                                 Caused by: java.lang.NullPointerException: Attempt to invoke virtual method 'int com.example.wildstone.cv_maker.Custom_Adapter_for_Language.getCount()' on a null object reference
                                                                                    at com.example.wildstone.cv_maker.Language_Activity.getListCount(Language_Activity.java:117)
                                                                                    at com.example.wildstone.cv_maker.Language_Activity.onCreate(Language_Activity.java:106)
                                                                                    at android.app.Activity.performCreate(Activity.java:6955)
                                                                                    at android.app.Instrumentation.callActivityOnCreate(Instrumentation.java:1126)
                                                                                    at android.app.ActivityThread.performLaunchActivity(ActivityThread.java:2927)
                                                                                    at android.app.ActivityThread.handleLaunchActivity(ActivityThread.java:3045) 
                                                                                    at android.app.ActivityThread.-wrap14(ActivityThread.java) 
                                                                                    at android.app.ActivityThread$H.handleMessage(ActivityThread.java:1642) 
                                                                                    at android.os.Handler.dispatchMessage(Handler.java:102) 
                                                                                    at android.os.Looper.loop(Looper.java:154) 
                                                                                    at android.app.ActivityThread.main(ActivityThread.java:6776) 
                                                                                    at java.lang.reflect.Method.invoke(Native Method) 
                                                                                    at com.android.internal.os.ZygoteInit$MethodAndArgsCaller.run(ZygoteInit.java:1496) 
                                                                                    at com.android.internal.os.ZygoteInit.main(ZygoteInit.java:1386)

You should not be setting `listView.setAdapter(arrayAdapter);` in an `onClickListener()`. You should be setting this as early as possible within `onCreate()` and then accessing the adapter accordingly later on. — Michael Dodd, Feb 14 '18 at 17:08
Better still, take a look at using `RecyclerView` instead of `ListView`: https://developer.android.com/guide/topics/ui/layout/recyclerview.html — Michael Dodd, Feb 14 '18 at 17:08
Thanks for pointing me to the "What is a NullPointerException, and how do I fix it?" @MichaelDodd i just understand why this problem occur .Will be careful in future — Saad Zahoor, Feb 14 '18 at 17:15

lib4 · Accepted Answer · 2018-02-14T17:14:24.863

array adapter is null until add_language button is clicked. But getListCount() method is getting called from onCreate.

You might need to change initialize arrayAdapter in onCreate before the getListCount method. The following lines should outside of the onClickListener.

    arrayAdapter = new Custom_Adapter_for_Language(Language_Activity.this , arr);
    listView.setAdapter(arrayAdapter);

Something like this onCreate Method:-

     arr = new ArrayList<>();
     arrayAdapter = new Custom_Adapter_for_Language(Language_Activity.this , arr);
     listView.setAdapter(arrayAdapter);

And in click listener, you just have to notify dataset

     add_language.setOnClickListener(new View.OnClickListener() {
                    @Override
                    public void onClick(View v) {
                     .
                     .
                    arrayAdapter.notifyDataSetChanged();
                  }

Thanks .It solved my problem – Saad Zahoor Feb 14 '18 at 17:21 — Saad Zahoor, Feb 14 '18 at 17:21

score 0 · Answer 2 · answered Feb 14 '18 at 17:09

            add_language.setOnClickListener(new View.OnClickListener() {
                @Override
                public void onClick(View v) {

                    arr.add(new Language_data_comes_here( R.mipmap.language , language.getText().toString()));

                    arrayAdapter = new Custom_Adapter_for_Language(Language_Activity.this , arr);

                    listView.setAdapter(arrayAdapter);

                    builder.setCancelable(true);
                    language.setText("");

                }
            });

This creates a new adapter each time you click the button. If the user does not click the button before trying to count the number of elements in the adapter, you will get the NPE.

To fix this, you should create a single adapter in onCreate(). Then when you add elements to the ArrayList, just call notifyDataSetChanged().

Can't get the count of the list item getting NullPointerException

2 Answers2