Android - sqllite

Finally into sqllite, i've been wondering where they put the database.

SQLiteDatabase is the base class for working with a SQLite database in Android and provides methods to open, query, update and close the database. More specifically SQLiteDatabase provides the insert(), update() and delete() methods. In addition it provides the execSQL() method, which allows to execute an SQL statement directly. The object ContentValues allows to define key/values. The "key" represents the table column identifier and the "value" represents the content for the table record in this column. ContentValues can be used for inserts and updates of database entries. Queries can be created via the rawQuery() and query() methods or via the SQLiteQueryBuilder class . rawQuery() directly accepts an SQL select statement as input. query() provides a structured interface for specifying the SQL query. SQLiteQueryBuilder is a convenience class that helps to build SQL queries.
MySQLiteHelper

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

public class MySQLiteHelper extends SQLiteOpenHelper {

public static final String TABLE_COMMENTS = "comments";
public static final String COLUMN_ID = "_id";
public static final String COLUMN_COMMENT = "comment";

private static final String DATABASE_NAME = "commments.db";
private static final int DATABASE_VERSION = 1;

// Database creation sql statement
private static final String DATABASE_CREATE = "create table "

  • TABLE_COMMENTS + "(" + COLUMN_ID
  • " integer primary key autoincrement, " + COLUMN_COMMENT
  • " text not null);";

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

@Override
public void onCreate(SQLiteDatabase database) {
database.execSQL(DATABASE_CREATE);
}

@Override
public void onUpgrade(SQLiteDatabase db, int oldVersion, int newVersion) {
Log.w(MySQLiteHelper.class.getName(),
"Upgrading database from version " + oldVersion + " to "

  • newVersion + ", which will destroy all old data");
    db.execSQL("DROP TABLE IF EXISTS " + TABLE_COMMENTS);
    onCreate(db);
    }

}

comment.java

public class Comment {
private long id;
private String comment;

public long getId() {
return id;
}

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

public String getComment() {
return comment;
}

public void setComment(String comment) {
this.comment = comment;
}

// Will be used by the ArrayAdapter in the ListView
@Override
public String toString() {
return comment;
}
} 

commentDataSource.java

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

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

public class CommentsDataSource {

// Database fields
private SQLiteDatabase database;
private MySQLiteHelper dbHelper;
private String[] allColumns = { MySQLiteHelper.COLUMN_ID,
MySQLiteHelper.COLUMN_COMMENT };

public CommentsDataSource(Context context) {
dbHelper = new MySQLiteHelper(context);
}

public void open() throws SQLException {
database = dbHelper.getWritableDatabase();
}

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

public Comment createComment(String comment) {
ContentValues values = new ContentValues();
values.put(MySQLiteHelper.COLUMN_COMMENT, comment);
long insertId = database.insert(MySQLiteHelper.TABLE_COMMENTS, null,
values);
Cursor cursor = database.query(MySQLiteHelper.TABLE_COMMENTS,
allColumns, MySQLiteHelper.COLUMN_ID + " = " + insertId, null,
null, null, null);
cursor.moveToFirst();
Comment newComment = cursorToComment(cursor);
cursor.close();
return newComment;
}

public void deleteComment(Comment comment) {
long id = comment.getId();
System.out.println("Comment deleted with id: " + id);
database.delete(MySQLiteHelper.TABLE_COMMENTS, MySQLiteHelper.COLUMN_ID
+ " = " + id, null);
}

public List getAllComments() {
List comments = new ArrayList();

Cursor cursor = database.query(MySQLiteHelper.TABLE_COMMENTS,
allColumns, null, null, null, null, null);

cursor.moveToFirst();
while (!cursor.isAfterLast()) {
Comment comment = cursorToComment(cursor);
comments.add(comment);
cursor.moveToNext();
}
// Make sure to close the cursor
cursor.close();
return comments;
}

private Comment cursorToComment(Cursor cursor) {
Comment comment = new Comment();
comment.setId(cursor.getLong(0));
comment.setComment(cursor.getString(1));
return comment;
}
} 

activity_main.xml