Unable to add more than one item in a listview

I am working on a tasks app, for which I created a list view that shows list items consitsting of task names, their priority etc. The data given to the list view is from an sqlite database. I, however, am unable to add more than one item to the list. I have no idea why. I have created a method to do so, but it doesn’t seem to work. I don’t know if the error is due to the database or my method itself. Even debugging didn’t help. Please note that I am using a list adapter since I am using a custom listview.

Code for Activity where list is shown :

package com.example.taskmasterv3;

import androidx.appcompat.app.AppCompatActivity;

import android.content.Context;
import android.database.Cursor;
import android.os.Bundle;
import android.view.LayoutInflater;
import android.widget.ListView;
import android.widget.TextView;

import java.util.ArrayList;

public class TaskSummary extends AppCompatActivity {

    ListView lvTaskList;
    TextView tvBreak, tvBreakAfterEvery, txt1, txt2, text1, hmm;
    TextView break_duration_mins;
    ArrayList<SubtaskPartTwo> subtaskList = new ArrayList<>();
    String subtname;
    String pri;
    String time;
    DBHelper dbHelper;






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

        lvTaskList = findViewById(R.id.lvTaskList);
        tvBreak = findViewById(R.id.tvBreak);
        tvBreakAfterEvery = findViewById(R.id.tvBreakAfterEvery);
        txt1 = findViewById(R.id.txt1);
        txt2 = findViewById(R.id.txt2);
        break_duration_mins = findViewById(R.id.break_duration_mins);
        text1 = findViewById(R.id.text1);
        hmm = findViewById(R.id.hmm);
        dbHelper = new DBHelper(this);







        subtname = getIntent().getStringExtra("subtaskname");
        pri = getIntent().getStringExtra("pri");
        time = getIntent().getStringExtra("time");

        
        // Using adapter for listview : 
        
        SubtaskDetailAdapter adapter = new SubtaskDetailAdapter(this, subtaskList);
        lvTaskList.setAdapter(adapter);
        SubtaskPartTwo subtaskPartTwo = new SubtaskPartTwo(subtname, pri, time);
        subtaskList.add(subtaskPartTwo);
        adapter.addANewSubTask(subtaskPartTwo);
















        double working_hours = getIntent().getIntExtra("working_hours", 1);
        double working_minutes = getIntent().getIntExtra("working_minutes", 0);
        double without_break_hours = getIntent().getIntExtra("without_break_hours", 1);
        double without_break_minutes = getIntent().getIntExtra("without_break_minutes", 0);
        double break_duration = getIntent().getIntExtra("break_duration", 20);
        String a = working_hours + " h";
        txt1.setText(a);
        String b = working_minutes + " m";
        break_duration_mins.setText(b);
        String c = break_duration + " m";
        txt2.setText(c);



        //Mathematics

        double g = working_hours * 100;
        double h = g + working_minutes;
        double i = h + break_duration;
        double j = i / 60;
        double p = (int) j;
        double q = j - p;
        double r = q * 60;

        without_break_hours = p;
        without_break_minutes = r;

        String d = without_break_hours + " h";
        String e = without_break_minutes + " m";

        text1.setText(d);
        hmm.setText(e);














    }



}

Code for Adapter Class :

package com.example.taskmasterv3;

import android.content.Context;
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 androidx.annotation.NonNull;
import androidx.annotation.Nullable;

import java.util.ArrayList;

public class SubtaskDetailAdapter extends ArrayAdapter<SubtaskPartTwo> {

    private final Context context;
    private ArrayList<SubtaskPartTwo> values;
    public boolean deleted;



    public SubtaskDetailAdapter(Context context, ArrayList<SubtaskPartTwo> list) {

        //since your are using custom view,pass zero and inflate the custom view by overriding getview

        super(context, 0 , list);
        this.context = context;
        this.values = list;


    }





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


        //check if its null, if so inflate it, else simply reuse it
        if (convertView == null) {
            LayoutInflater inflater = (LayoutInflater) context.getSystemService(Context.LAYOUT_INFLATER_SERVICE);
            convertView = inflater.inflate(R.layout.task_summary_item, parent, false);
        }

        //use convertView to refer the childviews to populate it with data
        TextView tvSubtaskName = convertView.findViewById(R.id.tvlolitaskname);
        ImageView ivPri = convertView.findViewById(R.id.ivloliPri);
        ImageView ivTime = convertView.findViewById(R.id.ivloliTime);





        tvSubtaskName.setText(values.get(position).getSubtaskName());

        if (values.get(position).getPri() == "h")
        {
            ivPri.setImageResource(R.drawable.priority_high);
        }
        if (values.get(position).getPri() == "m")
        {
            ivPri.setImageResource(R.drawable.priority_med);
        }
        if (values.get(position).getPri() == "l")
        {
            ivPri.setImageResource(R.drawable.priority_low);
        }

        if (values.get(position).getTime() == "more")
        {
            ivPri.setImageResource(R.drawable.time_symbol_more);
        }
        if (values.get(position).getPri() == "med")
        {
            ivPri.setImageResource(R.drawable.time_symbol_med);
        }
        if (values.get(position).getPri() == "less")
        {
            ivPri.setImageResource(R.drawable.time_symbol_less);
        }




        //return the view you inflated
        return convertView;
    }


    //to keep adding the new subtasks try the following
    public void addANewSubTask(SubtaskPartTwo newSubTask){
        ArrayList<SubtaskPartTwo> newvalues = new ArrayList<>(this.values);
        newvalues.add(newSubTask);
        this.values = newvalues;
        notifyDataSetChanged();


    }











    }

XML code for listview activity :

<?xml version="1.0" encoding="utf-8"?>
<androidx.constraintlayout.widget.ConstraintLayout xmlns:android="http://schemas.android.com/apk/res/android"
    xmlns:app="http://schemas.android.com/apk/res-auto"
    xmlns:tools="http://schemas.android.com/tools"
    android:id="@+id/parent"
    android:layout_width="match_parent"
    android:layout_height="match_parent"
    android:background="@color/background"
    tools:context=".TaskSummary">

    <!--  hello -->

    <ScrollView
        android:id="@+id/scrollView2"
        android:layout_width="wrap_content"
        android:layout_height="0dp"
        app:layout_constraintBottom_toBottomOf="parent"
        app:layout_constraintEnd_toEndOf="parent"
        app:layout_constraintStart_toStartOf="parent"
        app:layout_constraintTop_toTopOf="parent">


        <LinearLayout
            android:layout_width="match_parent"
            android:layout_height="wrap_content"
            android:orientation="vertical">

            <LinearLayout
                android:id="@+id/okay"
                android:layout_width="match_parent"
                android:layout_height="wrap_content"
                android:layout_margin="16dp"
                android:orientation="vertical">

                <ListView
                    android:id="@+id/lvTaskList"
                    android:layout_width="match_parent"
                    android:layout_height="wrap_content"
                    android:layout_margin="16dp">

                </ListView>


            </LinearLayout>

            <LinearLayout
                android:layout_width="wrap_content"
                android:layout_height="wrap_content"
                android:orientation="vertical">

                <LinearLayout
                    android:layout_width="match_parent"
                    android:layout_height="match_parent"
                    android:orientation="horizontal">

                    <LinearLayout
                        android:layout_width="wrap_content"
                        android:layout_height="wrap_content"
                        android:layout_weight="1"
                        android:orientation="horizontal">

                        <TextView
                            android:id="@+id/tvBreak"
                            android:layout_width="match_parent"

                            android:layout_height="match_parent"
                            android:layout_margin="8dp"
                            android:fontFamily="@font/roboto"
                            android:text="Total Working Time (Including Breaks)"
                            android:textColor="#B8AEAE"
                            android:textSize="20sp" />
                    </LinearLayout>

                    <LinearLayout
                        android:layout_width="match_parent"
                        android:layout_height="match_parent"
                        android:layout_weight="1"
                        android:orientation="horizontal">

                        <TextView
                            android:id="@+id/txt1"
                            android:layout_width="wrap_content"
                            android:layout_height="wrap_content"
                            android:layout_gravity="center"
                            android:layout_margin="8dp"
                            android:layout_weight="1"
                            android:fontFamily="@font/roboto"
                            android:gravity="right"
                            android:text="00 h"
                            android:textColor="#B8AEAE"
                            android:textSize="20sp" />

                        <TextView
                            android:id="@+id/break_duration_mins"
                            android:layout_width="wrap_content"
                            android:layout_height="wrap_content"
                            android:layout_gravity="center"
                            android:layout_marginTop="8dp"
                            android:layout_marginRight="8dp"
                            android:layout_marginBottom="8dp"
                            android:layout_weight="1"
                            android:gravity="left"
                            android:text="20 m"
                            android:textColor="#B8AEAE"
                            android:textSize="20sp" />
                    </LinearLayout>

                </LinearLayout>

                <!--  hello -->

                <!--  hello -->

                <LinearLayout
                    android:layout_width="match_parent"
                    android:layout_height="wrap_content"
                    android:layout_margin="16dp"
                    android:orientation="vertical">

                    <LinearLayout
                        android:layout_width="match_parent"
                        android:layout_height="match_parent"
                        android:orientation="horizontal">

                        <LinearLayout
                            android:layout_width="wrap_content"
                            android:layout_height="wrap_content"
                            android:layout_weight="1"
                            android:orientation="horizontal">

                            <TextView
                                android:id="@+id/tvWorktimeWithoutBreak"
                                android:layout_width="match_parent"
                                android:layout_height="match_parent"
                                android:layout_margin="8dp"
                                android:fontFamily="@font/roboto"
                                android:text="Work Time Before Each Break"
                                android:textColor="#B8AEAE"
                                android:textSize="20sp" />
                        </LinearLayout>

                        <LinearLayout
                            android:layout_width="match_parent"
                            android:layout_height="match_parent"
                            android:layout_weight="1"
                            android:orientation="horizontal">

                            <TextView
                                android:id="@+id/text1"
                                android:layout_width="wrap_content"
                                android:layout_height="wrap_content"
                                android:layout_gravity="center"
                                android:layout_margin="8dp"
                                android:layout_weight="1"
                                android:fontFamily="@font/roboto"
                                android:gravity="right"
                                android:text="00 h"
                                android:textColor="#B8AEAE"
                                android:textSize="20sp" />

                            <TextView
                                android:id="@+id/hmm"
                                android:layout_width="wrap_content"
                                android:layout_height="wrap_content"
                                android:layout_gravity="center"
                                android:layout_marginTop="8dp"
                                android:layout_marginRight="8dp"
                                android:layout_marginBottom="8dp"
                                android:layout_weight="1"
                                android:gravity="left"
                                android:text="20 m"
                                android:textColor="#B8AEAE"
                                android:textSize="20sp" />
                        </LinearLayout>

                    </LinearLayout>
                </LinearLayout>

                <!--  hello -->


                <LinearLayout
                    android:layout_width="match_parent"
                    android:layout_height="match_parent"
                    android:orientation="horizontal">

                    <TextView
                        android:id="@+id/tvBreakAfterEvery"
                        android:layout_width="wrap_content"
                        android:layout_height="wrap_content"
                        android:layout_marginLeft="8dp"
                        android:layout_marginTop="8dp"
                        android:layout_marginRight="8dp"
                        android:layout_marginBottom="8dp"
                        android:fontFamily="@font/roboto"
                        android:text="Break Duration"
                        android:textColor="#B8AEAE"
                        android:textSize="20sp"
                        app:layout_constraintBottom_toTopOf="@+id/lvTaskList"
                        app:layout_constraintEnd_toStartOf="@+id/lvTaskList"
                        app:layout_constraintStart_toStartOf="parent"
                        app:layout_constraintTop_toTopOf="parent" />

                    <TextView
                        android:id="@+id/txt2"
                        android:layout_width="match_parent"
                        android:layout_height="wrap_content"
                        android:layout_margin="8dp"
                        android:fontFamily="@font/roboto"
                        android:gravity="center_horizontal"
                        android:text="30 m"
                        android:textColor="#B8AEAE"
                        android:textSize="20sp" />
                </LinearLayout>

                <LinearLayout
                    android:layout_width="match_parent"
                    android:layout_height="wrap_content"
                    android:orientation="vertical">

                    <Button
                        android:id="@+id/btnStart"
                        android:layout_width="wrap_content"
                        android:layout_height="wrap_content"
                        android:layout_gravity="bottom|center_horizontal"
                        android:layout_margin="16dp"
                        android:text="Start" />
                </LinearLayout>
            </LinearLayout>
        </LinearLayout>
    </ScrollView>

</androidx.constraintlayout.widget.ConstraintLayout>

EDIT : Database Code

package com.example.taskmasterv3;


public class TaskInfo extends AppCompatActivity {


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


        
        tvTaskName = findViewById(R.id.tvTaskName);
        btnProceed = findViewById(R.id.btnProceed);
        dbHelper = new DBHelper(this);



        tvTaskName.setVisibility(View.INVISIBLE);

        if (tvTaskName.getText().equals(""))
        {
            tvTaskName.setClickable(false);
        }
        else
        {
            tvTaskName.setClickable(true);
        }





        btnSaveTaskName.setOnClickListener(new View.OnClickListener() {
            @Override
            public void onClick(View v) {
                tvTaskName.setVisibility(View.VISIBLE);
                tvTaskName.setText(etTaskName.getText().toString().toUpperCase().trim());
                etTaskName.setVisibility(View.GONE);
                btnSaveTaskName.setVisibility(View.GONE);
                btnNewSubtask.setEnabled(true);
            }
        });


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

                String tasksname = tvTaskName.getText().toString().trim();
                tvTaskName.setText("");
                etTaskName.setVisibility(View.VISIBLE);
                etTaskName.setText(tasksname);
                btnSaveTaskName.setVisibility(View.VISIBLE);
            }
        });



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

                Intent i2 = new Intent(TaskInfo.this, SubtaskActivity.class);
                startActivityForResult(i2, ENTER_SUBTASK);
                overridePendingTransition(R.anim.slide_in_up, R.anim.slide_out_up);

            }
        });


        // THE DATABASE PART 
        
        
        btnProceed.setOnClickListener(new View.OnClickListener() {
            @Override
            public void onClick(View v) {



                Cursor res = dbHelper.getdata();
                while(res != null && res.moveToNext()){
                    subtname = res.getString(0);
                     pri = res.getString(1);
                    time = res.getString(2);
                }







                if (etWorkingHours.getText().toString().isEmpty())
                {
                    etWorkingHours.setText("0");
                }
                if (etWorkingMinutes.getText().toString().isEmpty())
                {
                    etWorkingMinutes.setText("0");
                }
                if (etWorkinghrs.getText().toString().isEmpty())
                {
                    etWorkinghrs.setText("0");
                }
                if (etWorkingMins.getText().toString().isEmpty())
                {
                    etWorkingMins.setText("0");
                }

                int working_hours = Integer.parseInt(etWorkinghrs.getText().toString().trim());
                int working_minutes = Integer.parseInt(etWorkingMins.getText().toString().trim());
                int without_break_hours = Integer.parseInt(etWorkingHours.getText().toString().trim());
                int without_break_minutes = Integer.parseInt(etWorkingMinutes.getText().toString().trim());




                if (etWorkingHours.getText().toString().isEmpty() || etWorkingMinutes.getText().toString().isEmpty() || etWorkinghrs.getText().toString().isEmpty() || etWorkingMins.getText().toString().isEmpty())
                {
                    Toast.makeText(TaskInfo.this, "Field cannot be empty, please try again.", Toast.LENGTH_SHORT).show();

                }
                else
                {
                    if (working_hours != 0)
                    {
                        if (working_hours > without_break_hours)
                        {
                            int breaktime = Integer.parseInt(tvBreakTime.getText().toString());
                            Intent intent = new Intent(TaskInfo.this, TaskSummary.class);
                            intent.putExtra("working_hours", working_hours);
                            intent.putExtra("working_minutes", working_minutes);
                            intent.putExtra("without_break_hours", without_break_hours);
                            intent.putExtra("without_break_minutes", without_break_minutes);
                            intent.putExtra("break_duration", breaktime);
                            intent.putExtra("subtaskname", taskName);
                            intent.putExtra("priigh", NpriHigh);
                            intent.putExtra("primed", NpriMed);
                            intent.putExtra("prilow", NpriLow);
                            intent.putExtra("timemore", NtimeMore);
                            intent.putExtra("timemed", NtimeMed);
                            intent.putExtra("timeless", NtimeLess);
                            startActivity(intent);
                        }

                        if (working_hours == without_break_hours){

                            if (working_minutes >= without_break_minutes){
                                int breaktime = Integer.parseInt(tvBreakTime.getText().toString());
                                Intent intent = new Intent(TaskInfo.this, TaskSummary.class);
                                intent.putExtra("working_hours", working_hours);
                                intent.putExtra("working_minutes", working_minutes);
                                intent.putExtra("without_break_hours", without_break_hours);
                                intent.putExtra("without_break_minutes", without_break_minutes);
                                intent.putExtra("break_duration", breaktime);
                                intent.putExtra("subtaskname", taskName);
                                intent.putExtra("priigh", NpriHigh);
                                intent.putExtra("primed", NpriMed);
                                intent.putExtra("prilow", NpriLow);
                                intent.putExtra("timemore", NtimeMore);
                                intent.putExtra("timemed", NtimeMed);
                                intent.putExtra("timeless", NtimeLess);


                                intent.putExtra("subtaskname", subtname);
                                intent.putExtra("pri", pri);
                                intent.putExtra("time", time);

                                startActivity(intent);
                            }

                            if (working_minutes < without_break_minutes){

                                Toast.makeText(TaskInfo.this, "Invalid Time Entered", Toast.LENGTH_SHORT).show();

                            }



                        }

                        if (working_hours < without_break_hours){
                            Toast.makeText(TaskInfo.this, "Invalid Time Entered", Toast.LENGTH_SHORT).show();
                        }

                    }

                    if (working_hours == 0){

                        if (without_break_hours == 0)
                        {

                            if (working_minutes >= without_break_minutes){
                                int breaktime = Integer.parseInt(tvBreakTime.getText().toString());
                                Intent intent = new Intent(TaskInfo.this, TaskSummary.class);
                                intent.putExtra("working_hours", working_hours);
                                intent.putExtra("working_minutes", working_minutes);
                                intent.putExtra("without_break_hours", without_break_hours);
                                intent.putExtra("without_break_minutes", without_break_minutes);
                                intent.putExtra("break_duration", breaktime);
                                intent.putExtra("subtaskname", taskName);
                                intent.putExtra("prihigh", NpriHigh);
                                intent.putExtra("primed", NpriMed);
                                intent.putExtra("prilow", NpriLow);
                                intent.putExtra("timemore", NtimeMore);
                                intent.putExtra("timemed", NtimeMed);
                                intent.putExtra("timeless", NtimeLess);
                                startActivity(intent);
                            }

                            if (working_minutes < without_break_minutes){

                                Toast.makeText(TaskInfo.this, "Invalid Time Entered", Toast.LENGTH_SHORT).show();

                            }

                        }

                        if (without_break_hours != 0)
                        {
                            Toast.makeText(TaskInfo.this, "Invalid Time Entered", Toast.LENGTH_SHORT).show();
                        }
                    }
                }










            }
        });


      


    










       


            boolean delete = getIntent().getBooleanExtra("deleted", false);
            if (delete){

            }


        }


    }

  
   

    


        

       
    }






}

Answer

The problem is that you’re creating a new ArrayList while the adapter is left using the old one. That’s why notifyDataSetChanged() doesn’t work because the adapter’s backing list has not changed.

To fix this, update the values list directly

public void addANewSubTask(SubtaskPartTwo newSubTask) {
    this.values.add(newSubTask);
    notifyDataSetChanged();
}

or, add() through the adapter itself.

public void addANewSubTask(SubtaskPartTwo newSubTask) {
    add(newSubTask);
    notifyDataSetChanged();
}

---

Even if I add one item, it shows 2 (both the same)

It seems you’re adding the new element twice:

SubtaskPartTwo subtaskPartTwo = new SubtaskPartTwo(subtname, pri, time);

subtaskList.add(subtaskPartTwo);
adapter.addANewSubTask(subtaskPartTwo);

Just add via adapter only as it notifies as well. Check other places too for such duplicates.