Android Room迁移-java.lang.IllegalArgumentException：指定为非null的参数为null

Question

I am trying to add a column to an existing table in the database. The column is type ArrayList<Date> I wrote a migration step, increased database version number, and added the migration. When I run the migration (run the app), I get the error:

java.lang.IllegalArgumentException: Parameter specified as non-null is null: method kotlin.jvm.internal.Intrinsics.checkParameterIsNotNull, parameter value

when attempting to read data from that table.

I have tried following the steps here: https://medium.com/androiddevelopers/understanding-migrations-with-room-f01e04b07929

I have also tested with other data types, and it has migrated successfully. Seems like the issue is adding Lists or ArrayList s.

val MIGRATION_2_3 = object : Migration(2, 3) {
    override fun migrate(database: SupportSQLiteDatabase) {
        database.execSQL(
            "ALTER TABLE product ADD COLUMN ingredients TEXT"
        )
    }
}

Answer 1

You're altering a table without setting a default value. Therefore the default is null for all rows already present within the table. Since you require the Kotlin property to be non-null, you receive the IllegalArgumentException .

To resolve the issue, you'd have to alter the table to contain a default value for ingredients and declare it non-null as well.

val MIGRATION_2_3 = object : Migration(2, 3) {
    override fun migrate(database: SupportSQLiteDatabase) {
        database.execSQL(
            "ALTER TABLE product ADD COLUMN ingredients TEXT NOT NULL DEFAULT ''"
        )
    }
}

Alternatively you could make the ingredients Kotlin property nullable.