Delete Data with SQLite in Android

Create Project

Create new project in Android Studio with steps as below:

Step 1: Input Project Name and Select Project Location

Step 2: Select SDK for Android App

Step 3: Select Default Activity for App

Step 4: Finish create project

Add Strings

Open res\values\strings.xml file and add new string as below:

<resources>
    <string name="app_name">Learn Android with Real Apps</string>
    <string name="add_contact">Add Contact</string>
    <string name="id">Id</string>
    <string name="name">Name</string>
    <string name="phone">Phone</string>
    <string name="address">Address</string>
    <string name="email">Email</string>
    <string name="description">Description</string>
    <string name="save">Save</string>
    <string name="cancel">Cancel</string>
    <string name="insert_failed">Insert failed</string>
    <string name="update_failed">Update failed</string>
    <string name="delete_failed">Delete failed</string>
    <string name="delete">Delete</string>
    <string name="edit">Edit</string>
    <string name="are_you_sure">Are you sure?</string>
    <string name="confirm">Confirm</string>
    <string name="ok">OK</string>
</resources>

Create Context Menu

Create menu folder in res folder. Create crud_menu.xml file contains menus as below:

<?xml version="1.0" encoding="utf-8"?>
<menu xmlns:android="http://schemas.android.com/apk/res/android">

    <item
        android:id="@+id/editContactMenu"
        android:title="@string/edit" />

    <item
        android:id="@+id/deleteContactMenu"
        android:title="@string/delete" />

</menu>

Create Entities

Create new package named entities. In this package, create new java class named Contact.java as below:

package android.demo.entities;

import java.io.Serializable;

public class Contact implements Serializable {

    private int id;
    private String name;
    private String phone;
    private String address;
    private String email;
    private String description;

    public int getId() {
        return id;
    }

    public void setId(int id) {
        this.id = id;
    }

    public String getName() {
        return name;
    }

    public void setName(String name) {
        this.name = name;
    }

    public String getPhone() {
        return phone;
    }

    public void setPhone(String phone) {
        this.phone = phone;
    }

    public String getAddress() {
        return this.address;
    }

    public void setAddress(String address) {
        this.address = address;
    }

    public String getEmail() {
        return this.email;
    }

    public void setEmail(String email) {
        this.email = email;
    }

    public String getDescription() {
        return this.description;
    }

    public void setDescription(String description) {
        this.description = description;
    }
}

Create DatabaseHelper

Create new package named database. In this package, create new java class named DatabaseHelper.java as below:

package android.demo.database;

import android.content.Context;
import android.database.sqlite.SQLiteDatabase;
import android.database.sqlite.SQLiteOpenHelper;

public class DatabaseHelper extends SQLiteOpenHelper {

    private static String dbName = "ContactDB";
    private static int dbVersion = 1;

    private static String contactTable = "contact";

    private static String idColumn = "id";
    private static String nameColumn = "name";
    private static String phoneColumn = "phone";
    private static String addressColumn = "address";
    private static String emailColumn = "email";
    private static String descriptionColumn = "description";


    public DatabaseHelper(Context context) {
        super(context, dbName, null, dbVersion);
    }

    @Override
    public void onCreate(SQLiteDatabase sqLiteDatabase) {

        sqLiteDatabase.execSQL("create table " + contactTable + "(" +
                    idColumn + " integer primary key autoincrement, " +
                    nameColumn + " tex, " +
                    phoneColumn + " text, " +
                    addressColumn + " text, " +
                    emailColumn + " text, " +
                    descriptionColumn + " text " +
                ")"
        );

    }

    @Override
    public void onUpgrade(SQLiteDatabase sqLiteDatabase, int i, int i1) {
        sqLiteDatabase.execSQL("drop table if exists " + contactTable);
        onCreate(sqLiteDatabase);
    }

    public boolean delete(int id) {
        boolean result = true;
        try {
            SQLiteDatabase sqLiteDatabase = getWritableDatabase();
            result = sqLiteDatabase.delete(contactTable, idColumn + " = ?", new String[]{ String.valueOf(id) }) > 0;
        } catch (Exception e) {
            result = false;
        }
        return result;
    }

}

Main Activity Layout

Open res\layout\activity_main.xml file and create layout as below:

<?xml version="1.0" encoding="utf-8"?>
<LinearLayout 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:layout_width="match_parent"
    android:layout_height="match_parent"
    android:orientation="vertical"
    tools:context=".MainActivity">

    <ListView
        android:id="@+id/listViewContact"
        android:layout_width="match_parent"
        android:layout_height="match_parent" />

</LinearLayout>

Main Activity Class

Add code to MainActivity.java in android.demo.learnandroidwithrealapps package as below:

package android.demo.learnandroidwithrealapps;

import android.content.DialogInterface;
import android.content.Intent;
import android.demo.adapters.ContactListAdapter;
import android.demo.database.DatabaseHelper;
import android.demo.entities.Contact;
import android.os.Bundle;
import android.support.v7.app.AlertDialog;
import android.support.v7.app.AppCompatActivity;
import android.view.ContextMenu;
import android.view.Menu;
import android.view.MenuInflater;
import android.view.MenuItem;
import android.view.View;
import android.widget.AdapterView;
import android.widget.ListView;
import android.widget.TextView;
import android.widget.Toast;

import java.util.List;

public class MainActivity extends AppCompatActivity {

    private ListView listViewContact;

    @Override
    protected void onCreate(Bundle savedInstanceState) {
        super.onCreate(savedInstanceState);
        setContentView(R.layout.activity_main);
        initView();
        loadData();
    }

    private void initView() {
        listViewContact = findViewById(R.id.listViewContact);
        registerForContextMenu(listViewContact);
    }

    private void loadData() {
        DatabaseHelper databaseHelper = new DatabaseHelper(getApplicationContext());
        List<Contact> contacts = databaseHelper.findAll();
        if (contacts != null) {
            listViewContact.setAdapter(new ContactListAdapter(getApplicationContext(), contacts));
        }
    }

    @Override
    public void onCreateContextMenu(ContextMenu contextMenu, View view, ContextMenu.ContextMenuInfo menuInfo) {
        MenuInflater inflater = getMenuInflater();
        inflater.inflate(R.menu.crud_menu, contextMenu);
        super.onCreateContextMenu(contextMenu, view, menuInfo);
    }

    @Override
    public boolean onContextItemSelected(final MenuItem item) {
        if (item.getItemId() == R.id.deleteContactMenu) {
            AlertDialog.Builder builder = new AlertDialog.Builder(this);
            builder.setTitle(R.string.confirm);
            builder.setMessage(R.string.are_you_sure);
            builder.setPositiveButton(R.string.ok, new DialogInterface.OnClickListener() {
                @Override
                public void onClick(DialogInterface dialogInterface, int i) {
                    try {
                        AdapterView.AdapterContextMenuInfo adapterContextMenuInfo = (AdapterView.AdapterContextMenuInfo) item.getMenuInfo();
                        TextView textViewId = adapterContextMenuInfo.targetView.findViewById(R.id.textViewId);
                        int id = Integer.parseInt(textViewId.getText().toString());
                        DatabaseHelper databaseHelper = new DatabaseHelper(getApplicationContext());
                        if (databaseHelper.delete(id)) {
                            loadData();
                        } else {
                            Toast.makeText(getApplicationContext(), getText(R.string.delete_failed), Toast.LENGTH_LONG).show();
                        }
                    } catch (Exception e) {
                        Toast.makeText(getApplicationContext(), e.getMessage(), Toast.LENGTH_LONG).show();
                    }
                }
            });
            builder.setNegativeButton(R.string.cancel, new DialogInterface.OnClickListener() {
                @Override
                public void onClick(DialogInterface dialogInterface, int i) {
                    dialogInterface.dismiss();
                }
            });
            builder.show();
        }
        return super.onContextItemSelected(item);
    }
}

Structure of Project

Run App

Load Main Activity and Open Delete Menu

Display Confirm Dialog

Press OK Button Delete Data