Android迁移没有正确处理(列顺序错误)

Question

我正在使用Room数据库进行迁移。我得到了这个错误：

java.lang.IllegalStateException: Migration didn't properly handle coffee_productivity(io.github.omisie11.coffeeproductivitytracker.database.entity.CoffeeProductivityData).
 Expected:
TableInfo{name='coffee_productivity', columns={date=Column{name='date', type='TEXT', affinity='2', notNull=true, primaryKeyPosition=0}, id=Column{name='id', type='INTEGER', affinity='3', notNull=false, primaryKeyPosition=1}, productivity=Column{name='productivity', type='INTEGER', affinity='3', notNull=true, primaryKeyPosition=0}, coffees_volume=Column{name='coffees_volume', type='INTEGER', affinity='3', notNull=true, primaryKeyPosition=0}, number_of_coffees=Column{name='number_of_coffees', type='INTEGER', affinity='3', notNull=true, primaryKeyPosition=0}}, foreignKeys=[], indices=[Index{name='index_coffee_productivity_date', unique=true, columns=[date]}]}
 Found:
TableInfo{name='coffee_productivity', columns={date=Column{name='date', type='TEXT', affinity='2', notNull=true, primaryKeyPosition=0}, productivity=Column{name='productivity', type='INTEGER', affinity='3', notNull=true, primaryKeyPosition=0}, coffees_volume=Column{name='coffees_volume', type='INTEGER', affinity='3', notNull=false, primaryKeyPosition=0}, number_of_coffees=Column{name='number_of_coffees', type='INTEGER', affinity='3', notNull=true, primaryKeyPosition=0}, id=Column{name='id', type='INTEGER', affinity='3', notNull=false, primaryKeyPosition=1}}, foreignKeys=[], indices=[Index{name='index_coffee_productivity_date', unique=true, columns=[date]}]}

看起来列的顺序发生了变化，但我所做的唯一的事情就是添加一个新列。实体：

@Entity(tableName = "coffee_productivity", indices = [Index(value = "date", unique = true)])
data class CoffeeProductivityData(
@PrimaryKey(autoGenerate = true) var id: Long?,
@ColumnInfo(name = "date") var date: String,
@ColumnInfo(name = "productivity") var productivity: Int,
@ColumnInfo(name = "number_of_coffees") var numberOfCoffees: Int,
@ColumnInfo(name = "coffees_volume") var coffeesVolume: Int)
{
constructor() : this(null, "00/00/0000", 0, 0, 0)
}

数据库类：

@Database(entities = [CoffeeProductivityData::class], version = 2)
abstract class CoffeeProductivityDatabase : RoomDatabase() {

    abstract fun coffeeProductivityDao(): CoffeeProductivityDao

    companion object {
        private var dbInstance: CoffeeProductivityDatabase? = null

        private val MIGRATION_1_2: Migration = object : Migration(1, 2) {
            override fun migrate(database: SupportSQLiteDatabase) {
                database.execSQL("ALTER TABLE 'coffee_productivity' ADD COLUMN 'coffees_volume' INTEGER DEFAULT 0")
            }
        }

        fun getDatabase(context: Context): CoffeeProductivityDatabase? {
            if (dbInstance == null) {

                dbInstance = Room.databaseBuilder<CoffeeProductivityDatabase>(
                        context.applicationContext,
                        CoffeeProductivityDatabase::class.java,"coffee_productivity.db")
                        .addMigrations(MIGRATION_1_2)
                        .build()
            }
            return dbInstance
        }
    }
}

Answer 1

预期：

coffees_volume=Column{name='coffees_volume', type='INTEGER', affinity='3', notNull=true, primaryKeyPosition=0}

找到：

coffees_volume=Column{name='coffees_volume', type='INTEGER', affinity='3', notNull=false, primaryKeyPosition=0}

问题在于您的notNull属性。用以下代码替换您的模型：

@Entity(tableName = "coffee_productivity", indices = [Index(value = "date", unique = true)])
data class CoffeeProductivityData(
@PrimaryKey(autoGenerate = true) var id: Long?,
@ColumnInfo(name = "date") var date: String,
@ColumnInfo(name = "productivity") var productivity: Int,
@ColumnInfo(name = "number_of_coffees") var numberOfCoffees: Int,
@ColumnInfo(name = "coffees_volume") var coffeesVolume: Int? = 0)
{
   constructor() : this(null, "00/00/0000", 0, 0, 0)
}

Answer 2

请将查询替换为

ALTER TABLE 'coffee_productivity' ADD COLUMN 'coffees_volume' INTEGER NOT NULL DEFAULT 0

Answer 3

所发生的情况是，您通过添加字段或删除或更改迁移的名称和时间来更改表，这导致了这个问题，而没有将更改放在表中。但是他希望他的桌子是正确的，所以他发现了他所期望的不同，我就这样决定：

val MIGRATION_2_3 = object: Migration (2, 3) {
    override fun migrate (database: SupportSQLiteDatabase) {
        database.execSQL ("" "
                CREATE TABLE new_Song (
                    id INTEGER PRIMARY KEY NOT NULL,
                    name TEXT,
                    TEXT NOT NULL DEFAULT tag ''
                )
                "" ".trimIndent ())
        database.execSQL ("" "
                INSERT INTO new_Song (id, name, tag)
                SELECT id, name, tag FROM Song
                "" ".trimIndent ())
        database.execSQL ("DROP TABLE Song")
        database.execSQL ("ALTER TABLE new_Song RENAME TO Song")
    }
}

在页面的末尾，说明了“房间”官方网站的原因：https://developer.android.com/training/data-storage/room/migrating-db-versions?hl=en#kotlin