android - 使用@Parcelize时如何在数据类中分割构造函数以外的成员变量

Question

我正在使用 Room 和 Kotlin 数据类。比如，

@Entity(tableName = "Person")
@Parcelize
class Test(@ColumnInfo(name = "name") var name:String) : Parcelable{
    @PrimaryKey(autoGenerate = true)
    @ColumnInfo(name = "ID")
    var id: Long? = null
}

我可以使用构造函数创建实例并插入数据。我还收到警告 “property would not be serialized into a 'parcel'”。当我试图通过包发送对象时，id 丢失了，正如警告所说，这是预期的。如何在包裹中添加该成员 ID？我没有将 ID 保留在构造函数中，因为我希望它们自动生成。

Answer 1

您可以通过 documentation 找到此信息:

@Parcelize requires all serialized properties to be declared in the primary constructor. Android Extensions will issue a warning on each property with a backing field declared in the class body. Also, @Parcelize can't be applied if some of the primary constructor parameters are not properties.

If your class requires more advanced serialization logic, you can write it inside a companion class:

@Parcelize
data class User(val firstName: String, val lastName: String, val age: Int) : Parcelable {
    private companion object : Parceler<User> {
        override fun User.write(parcel: Parcel, flags: Int) {
            // Custom write implementation
        }

        override fun create(parcel: Parcel): User {
            // Custom read implementation
        }
    }
}