Is there a better way to pre-load items into a database?

Question

In my Android app I have a

1. SQLiteHelper class that extends SQLIteOpenHelper, and takes care of things like table-creation and upgrades.

2. SQLiteDatasource class that performs CRUD operations on the SQLiteHelper object.

I want to pre-load one of the tables with certain items so there is something present when the user first uses the app. These items may change so I want to make them modular.

Right now I am doing it this way:

public class MyDefaults {
    public static final ArrayList<HashMap<String, String>> MY_DEFAULTS;

    static {
        MY_DEFAULTS = new ArrayList<HashMap<String, String>>();
        HashMap<String, String> map = new HashMap<String, String>();

        //All the values below you change to whatever defaults you want
        map.clear();
        map.put(SQLiteHelper.KEY_1, "Value 1A");
        map.put(SQLiteHelper.KEY_2, "Value 2A");
        map.put(SQLiteHelper.KEY_3, "Value 3A");
        MY_DEFAULTS.add(new HashMap<String, String>(map));

        map.clear();
        map.put(SQLiteHelper.KEY_1, "Value 1B");
        map.put(SQLiteHelper.KEY_2, "Value 2B");
        map.put(SQLiteHelper.KEY_3, "Value 3B");
        MY_DEFAULTS.add(new HashMap<String, String>(map));

        map.clear();
        map.put(SQLiteHelper.KEY_1, "Value 1C");
        map.put(SQLiteHelper.KEY_2, "Value 2C");
        map.put(SQLiteHelper.KEY_3, "Value 3C");
        MY_DEFAULTS.add(new HashMap<String, String>(map));

        //and so on
    }

}

And then in my SQLiteDatasource class I have a method that performs the insert of these default values:

public void preloadDefaults() {
    mDatabase.beginTransaction();

    try {
        for (HashMap<String, String> map : MyDefaults.MY_DEFAULTS) {
            ContentValues values = new ContentValues();
            values.put(SQLiteHelper.KEY_1, map.get(SQLiteHelper.KEY_1));
            values.put(SQLiteHelper.KEY_2, map.get(SQLiteHelper.KEY_2));
            values.put(SQLiteHelper.KEY_3, map.get(SQLiteHelper.KEY_3));
            mDatabase.insert(SQLiteHelper.SOME_TABLE, null, values);
        }
    }
    finally {
        mDatabase.endTransaction();
    }
}

Is my way of doing this considered bad practice? Is there a better way to define the "defaults" that get inserted into a table after it gets created? Possibly through XML instead of a static class?

Note: I can't just copy an external DB because I'm actually inserting these fields with some other values created at runtime (the code above is a simplification of what my real code is).

Answer 1

As it is in this answer also The SQLiteAssetHelper library makes this task really simple.

It's easy to add as a gradle dependency (but a Jar is also available for Ant/Eclipse), and together with the documentation it can be found at:
https://github.com/jgilfelt/android-sqlite-asset-helper

As explained in documentation:

1. Add the dependency to your module's gradle build file:

   dependencies {
       compile 'com.readystatesoftware.sqliteasset:sqliteassethelper:+'
   }
   

2. Copy the database into the assets directory, in a subdirectory called assets/databases. For instance:
   assets/databases/my_database.db

   (Optionally, you may compress the database in a zip file such as assets/databases/my_database.zip. This isn't needed, since the APK is compressed as a whole already.)

3. Create a class, for example:

   public class MyDatabase extends SQLiteAssetHelper {
   
       private static final String DATABASE_NAME = "my_database.db";
       private static final int DATABASE_VERSION = 1;
   
       public MyDatabase(Context context) {
           super(context, DATABASE_NAME, null, DATABASE_VERSION);
       }
   }
   

Answer 2

You can memorize your data, with Serialize Objects. Read here:

How do I serialize an object and save it to a file in Android?