Android Room迁移：通过创建新表来更新属性名称

Question

Issue

In my project I a have a room table named ' content ' with a Double attribute ' archivedCount '. In the latest version of the app the attribute archivedCount attribute is re-named to dismissCount , still as type Double.

Android API Level / SQL Version

28 / 3.19

Original Content model

@Entity(tableName = "content")
data class Content(@PrimaryKey var id: String, var archiveCount: Double) : Parcelable {...}

New Content model

@Entity(tableName = "content")
data class Content(@PrimaryKey var id: String, var dismissCount: Double) : Parcelable {...}

Runtime error

java.lang.IllegalStateException: Migration didn't properly handle content(app.coinverse.content.models.Content).

I've inspected the Expected and Found tables the log prints and they appear to be identical.

Attempted Solution

I attempted the complex schema change as outlined by a Google Developer Advocate unsuccessfully in order to modify the name of one attribute / column. Here is a basic version of what I attempted.

val MIGRATION_1_2: Migration = object : Migration(1, 2) {
override fun migrate(database: SupportSQLiteDatabase) {
    // Create the new table
    database.execSQL("CREATE TABLE content_new (id TEXT, dismissCount REAL, PRIMARY KEY(id))")
    // Copy the data
    database.execSQL("INSERT INTO content_new (id, dismissCount) SELECT id, archiveCount FROM content")
    // Remove the old table
    database.execSQL("DROP TABLE content")
    // Change the table name to the correct one
    database.execSQL("ALTER TABLE content_new RENAME TO content")
}

}

Answer 1

看不到您的实现有什么问题，我建议您使用另一个未命名为Content（）的@Entity类，然后重试。