List item is deleted from ListView, but not from the database

Question

I have a custom ListView adapter. In the ListView I set a delete button.

Now I want to delete the fixed list item by clicking on that list's button. I have been able to delete it from the ListView. But when I refresh my layout activity, the list is shown in the same place.

Maybe it wasn't deleted from the database. I created the database in my main activity. But I deleted the list item from ListView adapter activity.

This is my ListView adapter:

import static com.example.shubho.digitalattendancesheet.Constant.FIRST_COLUMN;
import static com.example.shubho.digitalattendancesheet.Constant.SECOND_COLUMN;

public class ListViewAdapter extends BaseAdapter
{
public ArrayList<HashMap> list;
Activity activity;


public ListViewAdapter(Activity activity, ArrayList<HashMap> list) {
    super();
    this.activity = activity;
    this.list = list;
}

@Override
public int getCount() {
    // TODO Auto-generated method stub
    return list.size();
}

@Override
public Object getItem(int position) {
    // TODO Auto-generated method stub
    return list.get(position);
}

@Override
public long getItemId(int position) {
    // TODO Auto-generated method stub
    return 0;
}

private class ViewHolder {
    TextView txtFirst;
    TextView txtSecond;
}

@Override
public View getView(final int position, View convertView, ViewGroup parent) {
    // TODO Auto-generated method stub

    // TODO Auto-generated method stub
    final ViewHolder holder;
    LayoutInflater inflater =  activity.getLayoutInflater();


    if (convertView == null)
    {
        convertView = inflater.inflate(R.layout.course_display_row, null);
        holder = new ViewHolder();
        holder.txtFirst = (TextView) convertView.findViewById(R.id.t_code);
        holder.txtSecond = (TextView) convertView.findViewById(R.id.t_title);
        ImageButton delete = (ImageButton) convertView.findViewById(R.id.t_delete);

        convertView.setTag(holder);
        delete.setOnClickListener( new View.OnClickListener() {
                                    @Override
                                    public void onClick(View v) {
                                        list.remove(position);
                                        notifyDataSetChanged();



                                    }
                                }
        );
    }
    else
    {
        holder = (ViewHolder) convertView.getTag();
    }

    HashMap map = list.get(position);
    holder.txtFirst.setText((CharSequence) map.get(FIRST_COLUMN));
    holder.txtSecond.setText((CharSequence) map.get(SECOND_COLUMN));

    return convertView;
}

}

In my AddCourseActivity (main activity) I used:

public class AddCourseActivity extends AppCompatActivity implements View.OnClickListener{

EditText editCourseCode,editCourseTitle;
Button btnAdd,btnEdit,btnSearch,btnShowAll;
ImageButton btnDelete;

SQLiteDatabase db;
ListView listview;
int i;

ArrayList<String> ar =null;
ArrayList<String> ar1 =null;
ArrayList<String> SampleArrayList = new ArrayList<>();

private ArrayList<HashMap> list;

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

    Toolbar toolbar = (Toolbar) findViewById(R.id.toolbar);
    setSupportActionBar(toolbar);
    getSupportActionBar().setDisplayShowTitleEnabled(false);


    editCourseCode = (EditText)findViewById(R.id.courseCode);
    editCourseTitle = (EditText)findViewById(R.id.courseTitle);
    btnAdd = (Button)findViewById(R.id.add);
    btnShowAll = (Button)findViewById(R.id.show);
    btnEdit = (Button)findViewById(R.id.update);


    db = openOrCreateDatabase("CourseDB", Context.MODE_PRIVATE,null);
    db.execSQL("CREATE TABLE IF NOT EXISTS course(courseCode VARCHAR, courseTitle VARCHAR)");


    btnAdd.setOnClickListener(this);
    btnEdit.setOnClickListener(this);
    btnShowAll.setOnClickListener(this);
}
public void onClick(View view){
    if (view == btnAdd){
        String str = editCourseCode.getText().toString().trim();
        String str1 = editCourseTitle.getText().toString().trim();
        if(str.length()>0 && str1.length()>0){
            db.execSQL("insert into course values('" + str + "','" + str1 + "')");
            Snackbar.make(view, "Inserted", Snackbar.LENGTH_SHORT).show();
            editCourseCode.setText("");
            editCourseTitle.setText("");
        } else {
            Snackbar.make(view, "Not Inserted", Snackbar.LENGTH_SHORT).show();
        }
    }
    else if(view == btnShowAll){
        try {

            final ListView lview = (ListView) findViewById(R.id.list);
            populateList();
            final ListViewAdapter adapter = new ListViewAdapter(this, list);
            lview.setAdapter(adapter);


        } catch (Exception e) {
            Snackbar.make(view, "No record found", Snackbar.LENGTH_SHORT).show();
        }
    }
    else if(view==btnEdit){
        if(editCourseCode.getText().toString().trim().length()==0 && editCourseTitle.getText().toString().trim().length()==0){
            Snackbar.make(view, "Not Updated", Snackbar.LENGTH_SHORT).show();
            return;
        }
        else {
            if (editCourseCode.getText().toString().trim().length() != 0) {
                db.execSQL("UPDATE course set courseTitle='"+editCourseTitle.getText()+"' WHERE " + " courseCode ='"+editCourseCode.getText()+"'");
            }
            else if (editCourseTitle.getText().toString().trim().length() != 0) {
                db.execSQL("UPDATE course set courseCode='"+editCourseCode.getText()+"' WHERE " + " courseTitle ='"+editCourseTitle.getText()+"'");
            }
            Snackbar.make(view, "Updated", Snackbar.LENGTH_SHORT).show();
        }
    }
}
private void populateList() {
    // TODO Auto-generated method stub

    ar = new ArrayList();
    ar1 = new ArrayList();
    Cursor c = db.rawQuery("Select * from course", null);
    c.moveToFirst();

    do {
        ar.add(c.getString(c.getColumnIndex("courseCode")));
        ar1.add(c.getString(c.getColumnIndex("courseTitle")));
    } while (c.moveToNext());


    list = new ArrayList<HashMap>();
    for ( i = 0; i < ar.size(); i++) {

        HashMap temp = new HashMap();
        temp.put(FIRST_COLUMN, ar.get(i));
        temp.put(SECOND_COLUMN, ar1.get(i));
        list.add(temp);
    }

}







@Override
public boolean onCreateOptionsMenu(Menu menu) {

    getMenuInflater().inflate(R.menu.menu_add_course, menu);
    return true;
}

@Override
public boolean onOptionsItemSelected(MenuItem item) {
    // Handle item selection
    switch (item.getItemId()) {
        case R.id.action_profile:
            onBackPressed();
            return true;
        default:
            return super.onOptionsItemSelected(item);
    }
}




}

How can I delete the fixed list item from the database?

Answer 1

You just have to run a delete query in your database table as well when you are removing from the list. So the onClickListener should look like this.

ImageButton delete = (ImageButton) convertView.findViewById(R.id.t_delete);
convertView.setTag(holder);
delete.setOnClickListener(new View.OnClickListener() {
    @Override
    public void onClick(View v) {
        // Delete from database as well
        db.rawQuery("delete from course where courseCode = '" + list.get(position).get(FIRST_COLUMN) + "'", null);

        // Now delete from list and update your ListView
        list.remove(position);
        notifyDataSetChanged();
    }
});

Update

Based on the update of the question. I have modified your adapter and introduced some new variables in it. Please check the adapter and import the packages necessary in this adapter. Then modify the place from where you initiate the adapter.

public class ListViewAdapter extends BaseAdapter {
    private ArrayList<HashMap> list;
    private Context context;
    private SQLiteDatabase db;

    public ListViewAdapter(Context context, ArrayList<HashMap> list) {
        super();
        this.context = context;
        this.list = list;
    }

    @Override
    public int getCount() {
        return list.size();
    }

    @Override
    public Object getItem(int position) {
        return list.get(position);
    }

    @Override
    public long getItemId(int position) {
        return 0;
    }

    private class ViewHolder {
        TextView txtFirst;
        TextView txtSecond;
    }

    @Override
    public View getView(final int position, View convertView, ViewGroup parent) {
        final ViewHolder holder;

        if (convertView == null) {
            convertView = LayoutInflater.from(parent.getContext()).inflate(R.layout.course_display_row, null);
            holder = new ViewHolder();
            holder.txtFirst = (TextView) convertView.findViewById(R.id.t_code);
            holder.txtSecond = (TextView) convertView.findViewById(R.id.t_title);
            ImageButton delete = (ImageButton) convertView.findViewById(R.id.t_delete);

            convertView.setTag(holder);
            delete.setOnClickListener
                    (new View.OnClickListener() {
                         @Override
                         public void onClick(View v) {
                             db = context.openOrCreateDatabase("CourseDB", Activity.MODE_PRIVATE, null);
                             db.execSQL("DELETE from course where courseCode = '" + list.get(position).get(FIRST_COLUMN) + "'");
                             db.close();

                             list.remove(position);
                             notifyDataSetChanged();
                         }
                     }
                    );
        } else {
            holder = (ViewHolder) convertView.getTag();
        }

        HashMap map = list.get(position);
        holder.txtFirst.setText((CharSequence) map.get(FIRST_COLUMN));
        holder.txtSecond.setText((CharSequence) map.get(SECOND_COLUMN));

        return convertView;
    }
}

Hope that helps!

Answer 2

Create a Interface inside adapter class

interface OnDeleteListener {
    onDeleteCourse(String code, int position)
}

Add this constructor to Adapter class

private OnDeleteListenre mListener;    

public ListViewAdapter(List<HashMap> items, OnDeleteListener listener) {
    mListener = listener
    ...
}

Add this method inside Adapter class

public void refresh(int position) {
    // remove the item from the list
    list.remove(position)
    // refresh listview
    notifyDataSetChanged();
}

Change delete button implementation like below

delete.setOnClickListener(new View.OnClickListener() {
            @Override
            public void onClick(View view) {
                // get the course code from the list according to position
                ...
                ...
                // pass this code and item position here
                mListener.onDelete(## PASS COURSE CODE HERE ##, position);
            }
        });

Let the Activity class implement OnDeleteListener and

 @Override
public void onDeleteCourse(String code, int postion) {
   // Delete the course from the database here
   ...
   ... 
   // notify the adapter 
   adapter.refresh(position)
}

Initialize the Adapter

adapter = ListViewAdapter(list, this)

Answer 3

in OnClick for the delete button, create a worker thread and execute a db query to delete the item. You would need to uniquely identify the item in the list, so basically you need some sort of id on your item (which I presume you already have)

You can use AsyncTask, Handlers or Threads to do this. Don't execute db queries on main thread otherwise your app would lag.

On a side note. Stop using notifyDataSetChanged and instead use notifyItemRemoved.