Android's Architecture Components Version 0.4 by Mark L. Murphy

Author:Mark L. Murphy
Language: eng
Format: mobi, epub, pdf
Publisher: CommonsWare
Published: 2017-09-28T16:26:35+00:00

Creating a Database for a Schema Version

There are two main methods on MigrationTestHelper that we will use in testing. One is createDatabase(). This creates the database, as a specific database file, for a specific schema version… including any of our historical ones found in those schema JSON files. Here, we ask the helper to create a database named DB_NAME for schema version 1:

SupportSQLiteDatabase db=helper.createDatabase(DB_NAME, 1);

(from Trips/RoomMigrations/app/src/androidTest/java/com/commonsware/android/room/MigrationTests.java)

That SupportSQLiteDatabase object has an API reminiscent of a trimmed-down SQLiteDatabase. query() replaces rawQuery() and is used for executing arbitrary SQL SELECT statements. We also have execSQL(), insert(), update(), and delete(), for other operations.

As part of testing a migration, you will need to add some sample data to the database, using whatever schema you asked to be used, so that you can confirm that the migration worked as expected and did not wreck the existing data. This code will not be very Room-ish, but more like classic SQLite Android programming:

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