Databases In Android - Part 1

Android provides an easy way to connect to SQLite databases. It’s so easy, assuming you know how to query a database and follow some guides. But if you need to do anything more complicated than a few tables with low record counts you’ll find that there’s a lot more to it. Welcome to ContentProviders, CursorLoaders, and CursorAdapters. The good news is that a lot of these concepts translate into different environments besides Android.

In this post (this might end up being a multi-part series), I want to dive into how all these things work together, explore some alternatives, and go into some specific examples while keeping it relatively simple. I want this to be an overview of the concepts that can be referenced later on.

Getting Started With SQLite

If you know a little bit about writing queries, the SQLite part should be pretty easy. Generally you set up a contract class that models the schema of your database. The outer class defines the database, and the inner classes define each table. BaseColumns by the way is used to include _ID as a column name, so that your datababase plays nicely with certain Android classes like CursorAdapter.

If you’re starting out with a new app, you’ll need to insert a new class and call it something like databaseNameContract, or in my case ProductContract. Here’s an example from a sample database app I made:

public final class ProductContract {
    // private constructor prevents accidental instantiation of the contract class
    private ProductContract() {}

    // inner class defines the table
    public static class ProductEntry implements BaseColumns {
        public static final String TABLE_NAME = "product";
        public static final String COLUMN_NAME_NAME = "name";
    }
}

public class ProductHelper extends SQLiteOpenHelper {
    public static final int DATABASE_VERSION = 1;
    public static final String DATABASE_NAME = "products.db";
    private static final String SQL_CREATE_ENTRIES = "CREATE TABLE " + ProductEntry.TABLE_NAME + " (" +
            ProductEntry._ID + " INTEGER PRIMARY KEY," +
            ProductEntry.COLUMN_NAME_NAME + " TEXT)";

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

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

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