由于 属性 id 已成为必需,因此需要迁移

Migration is required due to Property id has been made required

如果我将 Payment.kt 和 CartPayment.kt 中的 lateinit var id: String 更改为 var id: String? = "",它工作正常,但问题是我想要 id 是必需的,如何我能做到吗?

错误:

java.lang.RuntimeException: Unable to create application: io.realm.exceptions.RealmMigrationNeededException: Migration is required due to the following errors:
    - Property 'CartPayment.id' has been made required.
    - Property 'Payment.id' has been made required.

型号:

open class Payment() : RealmObject() {

    @PrimaryKey
    lateinit var id: String
    var typeValue: Int = 0
    var statusValue: Int = 0
    var value: Double = 0.0
    var referenceNumber: String? = null

注意:除了 class 名称

之外,付款和购物车付款模式完全相同

Migration.kt

class Migration : RealmMigration {

    override fun migrate(realm: DynamicRealm, oldVersion: Long, newVersion: Long) {
        var oldVersion = oldVersion
        val schema = realm.schema

        if (oldVersion == 0L) {
            schema.create("Payment")
                .addField("id", String::class.java, FieldAttribute.PRIMARY_KEY)
                .addField("typeValue", Int::class.java)
                .addField("statusValue", Int::class.java)
                .addField("value", Double::class.java)
                .addField("referenceNumber", String::class.java)
            schema.get("Order")!!
                .addRealmListField("payments", schema.get("Payment")!!)
            oldVersion++
        }

        if (oldVersion == 1L) {
            schema.create("CartPayment")
                .addField("id", String::class.java, FieldAttribute.PRIMARY_KEY)
                .addField("typeValue", Int::class.java)
                .addField("statusValue", Int::class.java)
                .addField("value", Double::class.java)
                .addField("referenceNumber", String::class.java)
            schema.get("Order")!!
                .addField("cashPaymentAmount", Float::class.java)
                .addField("change", Float::class.java)
            oldVersion++
        }

    }
}

App.kt

class App: Application() {

    override fun onCreate() {
        super.onCreate()

        Realm.init(this)

        val realmConfig = RealmConfiguration.Builder()
            .schemaVersion(2)
            .migration(Migration())
            .build()
        Realm.getInstance(realmConfig)
        Realm.setDefaultConfiguration(realmConfig)

        Fresco.initialize(this)
    }
}

基本上,您要添加一个新字段 "id",它是主键(因此是必填键)。 如果在初始化(lateinit)时没有指定任何值,领域将如何迁移所有没有 id 但在迁移后需要的早期记录?因此错误。

以下解决方案可能有效

  1. 要么预填充 id(不使用 lateinit)
  2. 将您之前的记录转换为具有 ID(如果它们没有)

查看官方示例here

.addField("id", String::class.java, FieldAttribute.PRIMARY_KEY, FieldAttribute.REQUIRED) 成功了。

如果声明变量为lateinit,请务必添加FieldAttribute.REQUIRED.