Руководство Android SQLite Database

1- Что такое SQLite?

SQLite это реляционная база данных с открытым исходным кодом, построена на операционной системе  Android, поэтому вы можете ее использовать в любое время без дополнительных конфигураций.
Обычно, с такими базами данных как  Oracle, MySQL,.. вам нужна библиотека драйвера (Driver Libary), и подключить к JDBC, но с  SQLite в этом нет необходимости.

2- Содержание примера

Допустим вы создали приложение работающее на вашем  Android, это приложение сохраняет ваши заметки за день (Note). Вам нужна структура таблицы для хранения заметок.
  • Название таблицы: Note
Column Name Data Type Constraint Description
Note_Id int Primary Key Primary Key
Note_Title text   Note title
Note_Content text   Content
Пример:

3- Шаги для работы с SQLite Database

Вам нужно создать утилитерный класс для работы с базой данных  SQLite, этот класс расширен из класса  SQLiteOpenHelper. Существует 2 важных метода, которые вам нужно переопределить (override) это  onCreate() и onUpgrade().
  1. Создать class MyDatabaseHelper расширенный из SQLiteOpenHelper.
  2. После расширения class из SQLiteOpenHelper вам нужно переписать два метода onCreate() и onUpgrage()
    • onCreate() - Место где вы создаете таблицу. Вызывается (called) при создании базы данных.
    • onUpgrade() - Этот метод вызывается когда обновляется база данных, как как изменение структуры таблицы, добавление ограничений в базу данных и т.д.
MyDatabaseHelper.java
public class MyDatabaseHelper extends SQLiteOpenHelper {

// ....

public MyDatabaseHelper(Context context)  {
    super(context, DATABASE_NAME, null, DATABASE_VERSION);
}


@Override
public void onCreate(SQLiteDatabase db) {
    
    // Script to create table.
    String script = "CREATE TABLE " + TABLE_NOTE + "("
            + COLUMN_NOTE_ID + " INTEGER PRIMARY KEY," + COLUMN_NOTE_TITLE + " TEXT,"
            + COLUMN_NOTE_CONTENT + " TEXT" + ")";
    // Execute script.
    db.execSQL(script);
}


@Override
public void onUpgrade(SQLiteDatabase db, int oldVersion, int newVersion) {

    // Drop table
    db.execSQL("DROP TABLE IF EXISTS " + TABLE_NOTE);


    // Recreate
    onCreate(db);
}
// ...
}

4- Создать project & сделать дизайн интерфейса

Создайте  "Empty Activity" project с названием  SQLiteDemo для выполнения следующих примеров.
  • Name: SQLiteDemo
  • Package name: org.o7planning.sqlitedemo
Создать пустой  Activity.
  • File/New/Activity/Empty Activity
Ввoд:
  • Activity Name: AddEditNoteActivity
    • (Check Generate Layout File)
  • Layout: activity_add_edit_note
  • Package name: org.o7planning.sqlitedemo

activity_main.xml

activity_main.xml
<?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:layout_width="match_parent"
    android:layout_height="match_parent"
    tools:context=".MainActivity">

    <ListView
        android:id="@+id/listView"
        android:layout_width="0dp"
        android:layout_height="0dp"
        android:layout_marginStart="16dp"
        android:layout_marginLeft="16dp"
        android:layout_marginTop="16dp"
        android:layout_marginEnd="16dp"
        android:layout_marginRight="16dp"
        android:layout_marginBottom="16dp"
        app:layout_constraintBottom_toBottomOf="parent"
        app:layout_constraintEnd_toEndOf="parent"
        app:layout_constraintStart_toStartOf="parent"
        app:layout_constraintTop_toTopOf="parent" />
</androidx.constraintlayout.widget.ConstraintLayout>

activity_add_edit_note.xml

Настроить  ID, Text для компонентов на интерфейсе:
activity_add_edit_note.xml
<?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:layout_width="match_parent"
    android:layout_height="match_parent"
    tools:context=".AddEditNoteActivity">

    <EditText
        android:id="@+id/editText_note_title"
        android:layout_width="0dp"
        android:layout_height="wrap_content"
        android:layout_marginStart="16dp"
        android:layout_marginLeft="16dp"
        android:layout_marginTop="16dp"
        android:layout_marginEnd="16dp"
        android:layout_marginRight="16dp"
        android:ems="10"
        android:inputType="textPersonName"
        app:layout_constraintEnd_toEndOf="parent"
        app:layout_constraintStart_toStartOf="parent"
        app:layout_constraintTop_toTopOf="parent" />

    <EditText
        android:id="@+id/editText_note_content"
        android:layout_width="0dp"
        android:layout_height="0dp"
        android:layout_marginStart="16dp"
        android:layout_marginLeft="16dp"
        android:layout_marginTop="16dp"
        android:layout_marginEnd="16dp"
        android:layout_marginRight="16dp"
        android:layout_marginBottom="16dp"
        android:ems="10"
        android:inputType="textMultiLine"
        app:layout_constraintBottom_toTopOf="@+id/linearLayout3"
        app:layout_constraintEnd_toEndOf="parent"
        app:layout_constraintStart_toStartOf="parent"
        app:layout_constraintTop_toBottomOf="@+id/editText_note_title" />

    <LinearLayout
        android:id="@+id/linearLayout3"
        android:layout_width="0dp"
        android:layout_height="wrap_content"
        android:layout_marginStart="16dp"
        android:layout_marginLeft="16dp"
        android:layout_marginEnd="16dp"
        android:layout_marginRight="16dp"
        android:layout_marginBottom="16dp"
        android:orientation="horizontal"
        app:layout_constraintBottom_toBottomOf="parent"
        app:layout_constraintEnd_toEndOf="parent"
        app:layout_constraintStart_toStartOf="parent">

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

        <Button
            android:id="@+id/button_cancel"
            android:layout_width="wrap_content"
            android:layout_height="wrap_content"
            android:layout_weight="1"
            android:text="Cancel" />
    </LinearLayout>
</androidx.constraintlayout.widget.ConstraintLayout>

5- Java Code

Note.java
package org.o7planning.sqlitedemo.bean;

import java.io.Serializable;

public class Note implements Serializable {

    private int noteId;
    private String noteTitle;
    private String noteContent;

    public Note()  {

    }

    public Note(String noteTitle, String noteContent) {
        this.noteTitle= noteTitle;
        this.noteContent= noteContent;
    }

    public Note(int noteId, String noteTitle, String noteContent) {
        this.noteId= noteId;
        this.noteTitle= noteTitle;
        this.noteContent= noteContent;
    }

    public int getNoteId() {
        return noteId;
    }

    public void setNoteId(int noteId) {
        this.noteId = noteId;
    }
    public String getNoteTitle() {
        return noteTitle;
    }

    public void setNoteTitle(String noteTitle) {
        this.noteTitle = noteTitle;
    }


    public String getNoteContent() {
        return noteContent;
    }

    public void setNoteContent(String noteContent) {
        this.noteContent = noteContent;
    }


    @Override
    public String toString()  {
        return this.noteTitle;
    }

}
MyDatabaseHelper.java
package org.o7planning.sqlitedemo;

import android.content.ContentValues;
import android.content.Context;
import android.database.Cursor;
import android.database.sqlite.SQLiteDatabase;
import android.database.sqlite.SQLiteOpenHelper;
import android.util.Log;

import org.o7planning.sqlitedemo.bean.Note;

import java.util.ArrayList;
import java.util.List;


public class MyDatabaseHelper extends SQLiteOpenHelper {

    private static final String TAG = "SQLite";

    // Database Version
    private static final int DATABASE_VERSION = 1;

    // Database Name
    private static final String DATABASE_NAME = "Note_Manager";

    // Table name: Note.
    private static final String TABLE_NOTE = "Note";

    private static final String COLUMN_NOTE_ID ="Note_Id";
    private static final String COLUMN_NOTE_TITLE ="Note_Title";
    private static final String COLUMN_NOTE_CONTENT = "Note_Content";

    public MyDatabaseHelper(Context context)  {
        super(context, DATABASE_NAME, null, DATABASE_VERSION);
    }

    // Create table
    @Override
    public void onCreate(SQLiteDatabase db) {
        Log.i(TAG, "MyDatabaseHelper.onCreate ... ");
        // Script.
        String script = "CREATE TABLE " + TABLE_NOTE + "("
                + COLUMN_NOTE_ID + " INTEGER PRIMARY KEY," + COLUMN_NOTE_TITLE + " TEXT,"
                + COLUMN_NOTE_CONTENT + " TEXT" + ")";
        // Execute Script.
        db.execSQL(script);
    }


    @Override
    public void onUpgrade(SQLiteDatabase db, int oldVersion, int newVersion) {

        Log.i(TAG, "MyDatabaseHelper.onUpgrade ... ");
        // Drop older table if existed
        db.execSQL("DROP TABLE IF EXISTS " + TABLE_NOTE);

        // Create tables again
        onCreate(db);
    }


    // If Note table has no data
    // default, Insert 2 records.
    public void createDefaultNotesIfNeed()  {
        int count = this.getNotesCount();
        if(count ==0 ) {
            Note note1 = new Note("Firstly see Android ListView",
                    "See Android ListView Example in o7planning.org");
            Note note2 = new Note("Learning Android SQLite",
                    "See Android SQLite Example in o7planning.org");
            this.addNote(note1);
            this.addNote(note2);
        }
    }


    public void addNote(Note note) {
        Log.i(TAG, "MyDatabaseHelper.addNote ... " + note.getNoteTitle());

        SQLiteDatabase db = this.getWritableDatabase();

        ContentValues values = new ContentValues();
        values.put(COLUMN_NOTE_TITLE, note.getNoteTitle());
        values.put(COLUMN_NOTE_CONTENT, note.getNoteContent());

        // Inserting Row
        db.insert(TABLE_NOTE, null, values);

        // Closing database connection
        db.close();
    }


    public Note getNote(int id) {
        Log.i(TAG, "MyDatabaseHelper.getNote ... " + id);

        SQLiteDatabase db = this.getReadableDatabase();

        Cursor cursor = db.query(TABLE_NOTE, new String[] { COLUMN_NOTE_ID,
                        COLUMN_NOTE_TITLE, COLUMN_NOTE_CONTENT }, COLUMN_NOTE_ID + "=?",
                new String[] { String.valueOf(id) }, null, null, null, null);
        if (cursor != null)
            cursor.moveToFirst();

        Note note = new Note(Integer.parseInt(cursor.getString(0)),
                cursor.getString(1), cursor.getString(2));
        // return note
        return note;
    }


    public List<Note> getAllNotes() {
        Log.i(TAG, "MyDatabaseHelper.getAllNotes ... " );

        List<Note> noteList = new ArrayList<Note>();
        // Select All Query
        String selectQuery = "SELECT  * FROM " + TABLE_NOTE;

        SQLiteDatabase db = this.getWritableDatabase();
        Cursor cursor = db.rawQuery(selectQuery, null);

        // looping through all rows and adding to list
        if (cursor.moveToFirst()) {
            do {
                Note note = new Note();
                note.setNoteId(Integer.parseInt(cursor.getString(0)));
                note.setNoteTitle(cursor.getString(1));
                note.setNoteContent(cursor.getString(2));
                // Adding note to list
                noteList.add(note);
            } while (cursor.moveToNext());
        }

        // return note list
        return noteList;
    }

    public int getNotesCount() {
        Log.i(TAG, "MyDatabaseHelper.getNotesCount ... " );

        String countQuery = "SELECT  * FROM " + TABLE_NOTE;
        SQLiteDatabase db = this.getReadableDatabase();
        Cursor cursor = db.rawQuery(countQuery, null);

        int count = cursor.getCount();

        cursor.close();

        // return count
        return count;
    }


    public int updateNote(Note note) {
        Log.i(TAG, "MyDatabaseHelper.updateNote ... "  + note.getNoteTitle());

        SQLiteDatabase db = this.getWritableDatabase();

        ContentValues values = new ContentValues();
        values.put(COLUMN_NOTE_TITLE, note.getNoteTitle());
        values.put(COLUMN_NOTE_CONTENT, note.getNoteContent());

        // updating row
        return db.update(TABLE_NOTE, values, COLUMN_NOTE_ID + " = ?",
                new String[]{String.valueOf(note.getNoteId())});
    }

    public void deleteNote(Note note) {
        Log.i(TAG, "MyDatabaseHelper.updateNote ... " + note.getNoteTitle() );

        SQLiteDatabase db = this.getWritableDatabase();
        db.delete(TABLE_NOTE, COLUMN_NOTE_ID + " = ?",
                new String[] { String.valueOf(note.getNoteId()) });
        db.close();
    }

}
MainActivity.java
package org.o7planning.sqlitedemo;

import androidx.appcompat.app.AppCompatActivity;

import android.os.Bundle;
import android.app.Activity;
import android.app.AlertDialog;
import android.content.DialogInterface;
import android.content.Intent;
import android.view.ContextMenu;
import android.view.MenuItem;
import android.view.View;
import android.widget.AdapterView;
import android.widget.ArrayAdapter;
import android.widget.ListView;
import android.widget.Toast;

import org.o7planning.sqlitedemo.bean.Note;

import java.util.ArrayList;
import java.util.List;

public class MainActivity extends AppCompatActivity {

    private ListView listView;
    private static final int MENU_ITEM_VIEW = 111;
    private static final int MENU_ITEM_EDIT = 222;
    private static final int MENU_ITEM_CREATE = 333;
    private static final int MENU_ITEM_DELETE = 444;

    private static final int MY_REQUEST_CODE = 1000;

    private final List<Note> noteList = new ArrayList<Note>();
    private ArrayAdapter<Note> listViewAdapter;

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

        // Get ListView object from xml
        this.listView = (ListView) findViewById(R.id.listView);

        MyDatabaseHelper db = new MyDatabaseHelper(this);
        db.createDefaultNotesIfNeed();

        List<Note> list=  db.getAllNotes();
        this.noteList.addAll(list);


        // Define a new Adapter
        // 1 - Context
        // 2 - Layout for the row
        // 3 - ID of the TextView to which the data is written
        // 4 - the List of data

        this.listViewAdapter = new ArrayAdapter<Note>(this,
                android.R.layout.simple_list_item_1, android.R.id.text1, this.noteList);

        // Assign adapter to ListView
        this.listView.setAdapter(this.listViewAdapter);

        // Register the ListView for Context menu
        registerForContextMenu(this.listView);
    }


    @Override
    public void onCreateContextMenu(ContextMenu menu, View view,
                                    ContextMenu.ContextMenuInfo menuInfo)    {

        super.onCreateContextMenu(menu, view, menuInfo);
        menu.setHeaderTitle("Select The Action");

        // groupId, itemId, order, title
        menu.add(0, MENU_ITEM_VIEW , 0, "View Note");
        menu.add(0, MENU_ITEM_CREATE , 1, "Create Note");
        menu.add(0, MENU_ITEM_EDIT , 2, "Edit Note");
        menu.add(0, MENU_ITEM_DELETE, 4, "Delete Note");
    }

    @Override
    public boolean onContextItemSelected(MenuItem item){
        AdapterView.AdapterContextMenuInfo
                info = (AdapterView.AdapterContextMenuInfo) item.getMenuInfo();

        final Note selectedNote = (Note) this.listView.getItemAtPosition(info.position);

        if(item.getItemId() == MENU_ITEM_VIEW){
            Toast.makeText(getApplicationContext(),selectedNote.getNoteContent(),Toast.LENGTH_LONG).show();
        }
        else if(item.getItemId() == MENU_ITEM_CREATE){
            Intent intent = new Intent(this, AddEditNoteActivity.class);

            // Start AddEditNoteActivity, (with feedback).
            this.startActivityForResult(intent, MY_REQUEST_CODE);
        }
        else if(item.getItemId() == MENU_ITEM_EDIT ){
            Intent intent = new Intent(this, AddEditNoteActivity.class);
            intent.putExtra("note", selectedNote);

            // Start AddEditNoteActivity, (with feedback).
            this.startActivityForResult(intent,MY_REQUEST_CODE);
        }
        else if(item.getItemId() == MENU_ITEM_DELETE){
            // Ask before deleting.
            new AlertDialog.Builder(this)
                    .setMessage(selectedNote.getNoteTitle()+". Are you sure you want to delete?")
                    .setCancelable(false)
                    .setPositiveButton("Yes", new DialogInterface.OnClickListener() {
                        public void onClick(DialogInterface dialog, int id) {
                            deleteNote(selectedNote);
                        }
                    })
                    .setNegativeButton("No", null)
                    .show();
        }
        else {
            return false;
        }
        return true;
    }

    // Delete a record
    private void deleteNote(Note note)  {
        MyDatabaseHelper db = new MyDatabaseHelper(this);
        db.deleteNote(note);
        this.noteList.remove(note);
        // Refresh ListView.
        this.listViewAdapter.notifyDataSetChanged();
    }

    // When AddEditNoteActivity completed, it sends feedback.
    // (If you start it using startActivityForResult ())
    @Override
    protected void onActivityResult(int requestCode, int resultCode, Intent data) {
        super.onActivityResult(requestCode, resultCode, data);

        if (resultCode == Activity.RESULT_OK && requestCode == MY_REQUEST_CODE) {
            boolean needRefresh = data.getBooleanExtra("needRefresh", true);
            // Refresh ListView
            if (needRefresh) {
                this.noteList.clear();
                MyDatabaseHelper db = new MyDatabaseHelper(this);
                List<Note> list = db.getAllNotes();
                this.noteList.addAll(list);


                // Notify the data change (To refresh the ListView).
                this.listViewAdapter.notifyDataSetChanged();
            }
        }
    }

}

 
AddEditNoteActivity.java
package org.o7planning.sqlitedemo;

import androidx.appcompat.app.AppCompatActivity;
import android.os.Bundle;
import android.content.Intent;
import android.view.View;
import android.widget.Button;
import android.widget.EditText;
import android.widget.Toast;
import android.app.Activity;

import org.o7planning.sqlitedemo.bean.Note;

public class AddEditNoteActivity extends AppCompatActivity {

    private static final int MODE_CREATE = 1;
    private static final int MODE_EDIT = 2;

    private EditText textTitle;
    private EditText textContent;
    private Button buttonSave;
    private Button buttonCancel;

    private Note note;
    private boolean needRefresh;
    private int mode;

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

        this.textTitle = (EditText)this.findViewById(R.id.editText_note_title);
        this.textContent = (EditText)this.findViewById(R.id.editText_note_content);

        this.buttonSave = (Button)findViewById(R.id.button_save);
        this.buttonCancel = (Button)findViewById(R.id.button_cancel);

        this.buttonSave.setOnClickListener(new View.OnClickListener() {
            public void onClick(View v)  {
                 buttonSaveClicked();
            }
        });

        this.buttonCancel.setOnClickListener(new View.OnClickListener() {
            public void onClick(View v)  {
                buttonCancelClicked();
            }
        });

        Intent intent = this.getIntent();
        this.note = (Note) intent.getSerializableExtra("note");
        if(note== null)  {
            this.mode = MODE_CREATE;
        } else  {
            this.mode = MODE_EDIT;
            this.textTitle.setText(note.getNoteTitle());
            this.textContent.setText(note.getNoteContent());
        }
    }

    // User Click on the Save button.
    public void buttonSaveClicked()  {
        MyDatabaseHelper db = new MyDatabaseHelper(this);

        String title = this.textTitle.getText().toString();
        String content = this.textContent.getText().toString();

        if(title.equals("") || content.equals("")) {
            Toast.makeText(getApplicationContext(),
                    "Please enter title & content", Toast.LENGTH_LONG).show();
            return;
        }

        if(mode == MODE_CREATE ) {
            this.note= new Note(title,content);
            db.addNote(note);
        } else  {
            this.note.setNoteTitle(title);
            this.note.setNoteContent(content);
            db.updateNote(note);
        }

        this.needRefresh = true;

        // Back to MainActivity.
        this.onBackPressed();
    }

    // User Click on the Cancel button.
    public void buttonCancelClicked()  {
        // Do nothing, back MainActivity.
        this.onBackPressed();
    }

    // When completed this Activity,
    // Send feedback to the Activity called it.
    @Override
    public void finish() {

        // Create Intent
        Intent data = new Intent();

        // Request MainActivity refresh its ListView (or not).
        data.putExtra("needRefresh", needRefresh);

        // Set Result
        this.setResult(Activity.RESULT_OK, data);
        super.finish();
    }

}

6- Запуск приложения