Sqlite Database

Android SQLite is a very lightweight database which comes with Android OS and Android SQLite combines a clean SQL interface with a very small memory footprint and decent speed. In android SQLite is “baked into” the Android runtime and every Android application can create its own SQLite databases.

Android SQLite SQLiteOpenHelper

Android devices have features that can be available to handle changing local database schemas and which mostly depend on using the SQLiteOpenHelper class.

When the app runs the first time – At this point, we do not yet have a database. So we will have to create the tables, indexes, starter data, and so on, based on the requirements.
When the app is upgraded to a newer schema – Our database will still be on the old schema from the older edition of the app and you will have the option to alter the database schema to match the needs of the rest of the app.

SQLiteOpenHelper wraps up this logic to create and upgrade a database as per our specifications and that you will need to create a custom subclass of SQLiteOpenHelper implementing at least the following three methods.

Constructor : This takes the Context (e.g., an Activity), the name of the database, an optional cursor factory (we’ll discuss this later), and an integer representing the version of the database schema we are using.


public DatabaseHelper(Context context) { super(context, DB_NAME, null, DB_VERSION); }

onCreate(SQLiteDatabase db) : It’s also called when there is no database and the app needs one and It passes a SQLiteDatabase object and pointing to a newly-created database that you can populate with tables and initial data.
onUpgrade(SQLiteDatabase db, int oldVersion, int newVersion) : This function is called when the schema version we need does not match the schema version of the database and it passes a SQLiteDatabase’s object and the old and new version numbers. So you can figure out the best way to convert the database from the old schema to the new.

We can define a DBManager class to perform all database CRUD(Create, Read, Update and Delete) operations.

Opening and Closing Android SQLite Database Connection

Before performing any database operations like insert, update, delete records in a table, first open the database connection by calling getWritableDatabase() function as shown below:


public DBManager open() throws SQLException {
        dbHelper = new DatabaseHelper(context);
        database = dbHelper.getWritableDatabase();
        return this;
    }

The dbHelper is an instance of the subclass of SQLiteOpenHelper.
To close a database connection successfully, following method is called..

 public void close() {
        dbHelper.close();
    }

For inserting new Record into Android SQLite database table

The following code is showing how to insert a new record into the android local SQLite database.


public void insert(String name, String desc) {
        ContentValues contentValue = new ContentValues();
        contentValue.put(DatabaseHelper.SUBJECT, name);
        contentValue.put(DatabaseHelper.DESC, desc);
        database.insert(DatabaseHelper.TABLE_NAME, null, contentValue);
    }

Content Values creates an empty set of values using the given initial size and we’ll discuss the other values when we will jump into the coding part.

Updating Record in Android SQLite database table

The snippet shows how to update a single record.


public int update(long _id, String name, String desc) {
        ContentValues contentValues = new ContentValues();
        contentValues.put(DatabaseHelper.SUBJECT, name);
        contentValues.put(DatabaseHelper.DESC, desc);
        int i = database.update(DatabaseHelper.TABLE_NAME, contentValues, DatabaseHelper._ID + " = " + _id, null);
        return i;
    }

Android SQLite – Deleting a Record

We just need to pass the id of the record to delete as shown below.

public void delete(long _id) {
        database.delete(DatabaseHelper.TABLE_NAME, DatabaseHelper._ID + "=" + _id, null);
    }

Android SQLite Cursor

A Cursor represents the complete result set of the query. Once the query fetches a call to cursor.moveToFirst() is made and Call to moveToFirst() does two things:

This allows us to validate whether the query returned an empty set.
Basically, It moves the cursor to first result (when the set is not empty)

The following code is used to fetch all records:


public Cursor fetch() {
        String[] columns = new String[] { DatabaseHelper._ID, DatabaseHelper.SUBJECT, DatabaseHelper.DESC };
        Cursor cursor = database.query(DatabaseHelper.TABLE_NAME, columns, null, null, null, null, null);
        if (cursor != null) {
            cursor.moveToFirst();
        }
        return cursor;
    }

Another way to use a Cursor is to wrap it in a CursorAdapter and Just as ArrayAdapter adapts arrays, CursorAdapter adapts Cursor objects, making their data available to an AdapterView like a ListView.

Let’s jump to our android app project that can use SQLite to store some meaningful data.

Android SQLite Project Code

The application consists of 5 classes and We begin with defining with DatabaseHelper, which is a subclass of SQLiteOpenHelper as it is showing:

DatabaseHelper.java

package com.salesforcedriller.sqlite;

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

public class DatabaseHelper extends SQLiteOpenHelper {

    // Table Name
    public static final String TABLE_NAME = "COUNTRIES";

    // Table columns
    public static final String _ID = "_id";
    public static final String SUBJECT = "subject";
    public static final String DESC = "description";

    // Database Information
    static final String DB_NAME = "SALESFORCE_DRILLERS.DB";

    // database version
    static final int DB_VERSION = 1;

    // Creating table query
    private static final String CREATE_TABLE = "create table " + TABLE_NAME + "(" + _ID
            + " INTEGER PRIMARY KEY AUTOINCREMENT, " + SUBJECT + " TEXT NOT NULL, " + DESC + " TEXT);";

    public DatabaseHelper(Context context) {
        super(context, DB_NAME, null, DB_VERSION);
    }

    @Override
    public void onCreate(SQLiteDatabase db) {
        db.execSQL(CREATE_TABLE);
    }

    @Override
    public void onUpgrade(SQLiteDatabase db, int oldVersion, int newVersion) {
        db.execSQL("DROP TABLE IF EXISTS " + TABLE_NAME);
        onCreate(db);
    }
}

As discussed above we just have overridden the onCreate() and onUpgrade() function besides the constructor and We have assigned the names to the local database and the table as JOURNALDEV_COUNTRIES.DB and COUNTRIES respectively so The index column is auto incremented whenever a new row is inserted and The column names for country and currency are “subject” and “description”.

The DBManager class is where the DatabaseHelper has been initialized and the CRUD Operations are defined and Below is the code for this class:

DBManager.java

import android.content.ContentValues;
import android.content.Context;
import android.database.Cursor;
import android.database.SQLException;
import android.database.sqlite.SQLiteDatabase;

public class DBManager {

    private DatabaseHelper dbHelper;

    private Context context;

    private SQLiteDatabase database;

    public DBManager(Context c) {
        context = c;
    }

    public DBManager open() throws SQLException {
        dbHelper = new DatabaseHelper(context);
        database = dbHelper.getWritableDatabase();
        return this;
    }

    public void close() {
        dbHelper.close();
    }

    public void insert(String name, String desc) {
        ContentValues contentValue = new ContentValues();
        contentValue.put(DatabaseHelper.SUBJECT, name);
        contentValue.put(DatabaseHelper.DESC, desc);
        database.insert(DatabaseHelper.TABLE_NAME, null, contentValue);
    }

    public Cursor fetch() {
        String[] columns = new String[] { DatabaseHelper._ID, DatabaseHelper.SUBJECT, DatabaseHelper.DESC };
        Cursor cursor = database.query(DatabaseHelper.TABLE_NAME, columns, null, null, null, null, null);
        if (cursor != null) {
            cursor.moveToFirst();
        }
        return cursor;
    }

    public int update(long _id, String name, String desc) {
        ContentValues contentValues = new ContentValues();
        contentValues.put(DatabaseHelper.SUBJECT, name);
        contentValues.put(DatabaseHelper.DESC, desc);
        int i = database.update(DatabaseHelper.TABLE_NAME, contentValues, DatabaseHelper._ID + " = " + _id, null);
        return i;
    }

    public void delete(long _id) {
        database.delete(DatabaseHelper.TABLE_NAME, DatabaseHelper._ID + "=" + _id, null);
    }

}

The CountryListActivity.java class is the android activity which is launched when the application starts and Below is layout defined for it:

fragment_emp_list.xml

Here a ListView component is defined for including the records stored in the local database and Initially the ListView would be empty so a TextView is used to display the same.

CountryListActivity.java

import android.content.Intent;
import android.database.Cursor;
import android.os.Bundle;
import android.support.v4.widget.SimpleCursorAdapter;
import android.support.v7.app.ActionBarActivity;
import android.view.Menu;
import android.view.MenuItem;
import android.view.View;
import android.widget.AdapterView;
import android.widget.ListView;
import android.widget.TextView;

public class CountryListActivity extends ActionBarActivity {

    private DBManager dbManager;

    private ListView listView;

    private SimpleCursorAdapter adapter;

    final String[] from = new String[] { DatabaseHelper._ID,
            DatabaseHelper.SUBJECT, DatabaseHelper.DESC };

    final int[] to = new int[] { R.id.id, R.id.title, R.id.desc };

    @Override
    protected void onCreate(Bundle savedInstanceState) {
        super.onCreate(savedInstanceState);

        setContentView(R.layout.fragment_emp_list);

        dbManager = new DBManager(this);
        dbManager.open();
        Cursor cursor = dbManager.fetch();

        listView = (ListView) findViewById(R.id.list_view);
        listView.setEmptyView(findViewById(R.id.empty));

        adapter = new SimpleCursorAdapter(this, R.layout.activity_view_record, cursor, from, to, 0);
        adapter.notifyDataSetChanged();

        listView.setAdapter(adapter);

        // OnCLickListiner For List Items
        listView.setOnItemClickListener(new AdapterView.OnItemClickListener() {
            @Override
            public void onItemClick(AdapterView parent, View view, int position, long viewId) {
                TextView idTextView = (TextView) view.findViewById(R.id.id);
                TextView titleTextView = (TextView) view.findViewById(R.id.title);
                TextView descTextView = (TextView) view.findViewById(R.id.desc);

                String id = idTextView.getText().toString();
                String title = titleTextView.getText().toString();
                String desc = descTextView.getText().toString();

                Intent modify_intent = new Intent(getApplicationContext(), ModifyCountryActivity.class);
                modify_intent.putExtra("title", title);
                modify_intent.putExtra("desc", desc);
                modify_intent.putExtra("id", id);

                startActivity(modify_intent);
            }
        });
    }

    @Override
    public boolean onCreateOptionsMenu(Menu menu) {
        getMenuInflater().inflate(R.menu.main, menu);
        return true;
    }

    @Override
    public boolean onOptionsItemSelected(MenuItem item) {

        int id = item.getItemId();
        if (id == R.id.add_record) {

            Intent add_mem = new Intent(this, AddCountryActivity.class);
            startActivity(add_mem);

        }
        return super.onOptionsItemSelected(item);
    }

}

In this activity screen the DBManager class is invoked to perform the CRUD Operations.
A SimpleCursorAdapter is defined to add elements to the list from the query results that can be returned in an Cursor Object.

On list item click an intent is used to open the ModifyCountryActivity class.

The menu holds an item to add a new record from the ActionBar and an intent is performed to open the AddCountryActivity class. Below is menu.xml code.

menu.xml


<menu xmlns:android="https://schemas.android.com/apk/res/android"
    xmlns:app="https://schemas.android.com/apk/res-auto"
    xmlns:tools="https://schemas.android.com/tools"
    tools:context="com.example.sqlitesample.MainActivity" >

    <item
        android:id="@+id/add_record"
        android:icon="@android:drawable/ic_menu_add"
        android:orderInCategory="100"
        android:title="@string/add_record"
        app:showAsAction="always"/>

</menu>

The xml of layout and code of AddCountryActivity.java file are defined below:

activity_add_record.xml


<?xml version="1.0" encoding="utf-8"?>
<LinearLayout xmlns:android="https://schemas.android.com/apk/res/android"
    android:layout_width="match_parent"
    android:layout_height="match_parent"
    android:orientation="vertical"
    android:padding="20dp" >

    <EditText
        android:id="@+id/subject_edittext"
        android:layout_width="match_parent"
        android:layout_height="wrap_content"
        android:ems="10"
        android:hint="@string/enter_title" >

        <requestFocus />
    </EditText>

    <EditText
        android:id="@+id/description_edittext"
        android:layout_width="match_parent"
        android:layout_height="wrap_content"
        android:ems="10"
        android:hint="@string/enter_desc"
        android:inputType="textMultiLine"
        android:minLines="5" >
    </EditText>

    <Button
        android:id="@+id/add_record"
        android:layout_width="wrap_content"
        android:layout_height="wrap_content"
        android:layout_gravity="center"
        android:text="@string/add_record" />

</LinearLayout>

Two EditText components can take the inputs for country and currency along with a button to add the values to the database and display it in the ListView.

AddCountryActivity.java

import android.app.Activity;
import android.content.Intent;
import android.os.Bundle;
import android.view.View;
import android.view.View.OnClickListener;
import android.widget.Button;
import android.widget.EditText;

public class AddCountryActivity extends Activity implements OnClickListener {

    private Button addTodoBtn;
    private EditText subjectEditText;
    private EditText descEditText;

    private DBManager dbManager;

    @Override
    protected void onCreate(Bundle savedInstanceState) {
        super.onCreate(savedInstanceState);

        setTitle("Add Record");

        setContentView(R.layout.activity_add_record);

        subjectEditText = (EditText) findViewById(R.id.subject_edittext);
        descEditText = (EditText) findViewById(R.id.description_edittext);

        addTodoBtn = (Button) findViewById(R.id.add_record);

        dbManager = new DBManager(this);
        dbManager.open();
        addTodoBtn.setOnClickListener(this);
    }

    @Override
    public void onClick(View v) {
        switch (v.getId()) {
            case R.id.add_record:

                final String name = subjectEditText.getText().toString();
                final String desc = descEditText.getText().toString();

                dbManager.insert(name, desc);

                Intent main = new Intent(AddCountryActivity.this, CountryListActivity.class)
                        .setFlags(Intent.FLAG_ACTIVITY_CLEAR_TOP);

                startActivity(main);
                break;
        }
    }

}

The CRUD operation can be performed here, a new record to the database.
The xml of layout and code of ModifyCountryActivity.java file are defined below:

activity_modify_record.xml


<?xml version="1.0" encoding="utf-8"?>
<LinearLayout xmlns:android="https://schemas.android.com/apk/res/android"
    android:layout_width="match_parent"
    android:layout_height="match_parent"
    android:orientation="vertical"
    android:padding="10dp" >

    <EditText
        android:id="@+id/subject_edittext"
        android:layout_width="match_parent"
        android:layout_height="wrap_content"
        android:layout_marginBottom="10dp"
        android:ems="10"
        android:hint="@string/enter_title" />

    <EditText
        android:id="@+id/description_edittext"
        android:layout_width="match_parent"
        android:layout_height="wrap_content"
        android:ems="10"
        android:hint="@string/enter_desc"
        android:inputType="textMultiLine"
        android:minLines="5" >
    </EditText>


    <LinearLayout
        android:layout_width="fill_parent"
        android:layout_height="wrap_content"
        android:weightSum="2"
        android:gravity="center_horizontal"
        android:orientation="horizontal" >

        <Button
            android:id="@+id/btn_update"
            android:layout_width="wrap_content"
            android:layout_height="wrap_content"
            android:layout_weight="1"
            android:text="@string/btn_update" />

        <Button
            android:id="@+id/btn_delete"
            android:layout_width="wrap_content"
            android:layout_height="wrap_content"
            android:layout_weight="1"
            android:text="@string/btn_delete" />
    </LinearLayout>

</LinearLayout>

It’s the same as the previous layout except that modify and delete buttons are added.

ModifyCountryActivity.java

import android.app.Activity;
import android.content.Intent;
import android.os.Bundle;
import android.view.View;
import android.view.View.OnClickListener;
import android.widget.Button;
import android.widget.EditText;

public class ModifyCountryActivity extends Activity implements OnClickListener {

    private EditText titleText;
    private Button updateBtn, deleteBtn;
    private EditText descText;

    private long _id;

    private DBManager dbManager;

    @Override
    protected void onCreate(Bundle savedInstanceState) {
        super.onCreate(savedInstanceState);

        setTitle("Modify Record");

        setContentView(R.layout.activity_modify_record);

        dbManager = new DBManager(this);
        dbManager.open();

        titleText = (EditText) findViewById(R.id.subject_edittext);
        descText = (EditText) findViewById(R.id.description_edittext);

        updateBtn = (Button) findViewById(R.id.btn_update);
        deleteBtn = (Button) findViewById(R.id.btn_delete);

        Intent intent = getIntent();
        String id = intent.getStringExtra("id");
        String name = intent.getStringExtra("title");
        String desc = intent.getStringExtra("desc");

        _id = Long.parseLong(id);

        titleText.setText(name);
        descText.setText(desc);

        updateBtn.setOnClickListener(this);
        deleteBtn.setOnClickListener(this);
    }

    @Override
    public void onClick(View v) {
        switch (v.getId()) {
            case R.id.btn_update:
                String title = titleText.getText().toString();
                String desc = descText.getText().toString();

                dbManager.update(_id, title, desc);
                this.returnHome();
                break;

            case R.id.btn_delete:
                dbManager.delete(_id);
                this.returnHome();
                break;
        }
    }

    public void returnHome() {
        Intent home_intent = new Intent(getApplicationContext(), CountryListActivity.class)
                .setFlags(Intent.FLAG_ACTIVITY_CLEAR_TOP);
        startActivity(home_intent);
    }
}

The CRUD operations performed here which can be updating and deleting a record.
The below images are the screenshots of the final output of our android app.
The first image is the result seen when the app is launched for the first time.

Here in the second image is the output of clicking the menu option from the ActionBar to add a new record as shown below.

Here third image shows an output when 3 records are added :

Learn Android

Sqlite Database