ROOM无法弄清楚如何将该字段保存到数据库中 [英] ROOM Cannot figure out how to save this field into database

问题描述

我需要你的帮助. 我尝试在不进行反序列化的情况下找到解决方案，但没有发现任何问题. 如果您能帮助我，那就太好了... 所以我有这个以下JSON文件

I need your help. I try to find the solution without deserialize but I didn't find nothing. It would be nice if you can help me... So I have this following JSON file

"resources": [{
    "id": 441988,
    "name": "TVA",
    "parent": {
      "id": 159
    },
  },
  {
    "id": 441900,
    "name": "Marketing",
    "parent": {
      "id": 166
    },
}]

我用ROOM创建了一个数据库，它可以工作，但是我有一个问题， 无法保存父对象的ID"

I used ROOM to create a database, it works but I have one problem, its impossible to save "id of Parent object"

这是我的以下代码:

    @Entity(tableName = "resources")
    class CategoryBean {

    @PrimaryKey
    @ColumnInfo(name = "resource_id")
    @SerializedName("id")
    private var mId: Int = 0

    @ColumnInfo(name = "name")
    @SerializedName("name")
    private var mName: String? = null

    @ColumnInfo(name = "parent")
    @SerializedName("parent")
    private var mParent: ParentBean? = null

    fun getId(): Int {
        return mId
    }

    fun getName(): String? {
        return mName
    }

    fun getParent(): ParentBean? {
        return mParent
    }

    fun setParent(parent: ParentBean) {
        mParent = parent
    }

    fun setId(id: Int) {
        mId = id
    }

    fun setName(name: String) {
        mName = name
    }

在这里您可以找到我的ParentBean文件

Here you can find my ParentBean file

class ParentBean {

    @SerializedName("id")
    private var mId: Int = 0

    fun getId(): Int? {
        return mId
    }

}

我找到了一些列表的解决方案，但没有找到子对象的解决方案.

I found some solution for a list, but not for sub object.

感谢您的时间和帮助.

有我以下错误:

Cannot figure out how to save this field into database. You can consider adding a type converter for it.

推荐答案

Room在SQLite数据库上运行，当您将类注释为@Entity时，您正在创建一个表，该表的列根据类，因此您不能直接存储ParentBean之类的自定义类型，为此，您需要将mParent属性注释为@Embedded:

Room works on top of a SQLite database, when you annotate a class as @Entity you are creating a table whose columns are defined according to the properties of the class, so you can't store directly a custom type like ParentBean, to do that, you need to annotate mParent property as @Embedded:

@Entity(tableName = "resources")
class CategoryBean constructor(
    @PrimaryKey
    @ColumnInfo(name = "resource_id")
    @SerializedName("id")
    var mId: Int,
    @ColumnInfo(name = "name")
    @SerializedName("name")
    var mName: String?,
    @SerializedName("parent")
    @Embedded
    var mParent: ParentBean?
)

然后在ParentBean中为属性定义列名:

Then you define a column name for the property in ParentBean:

data class ParentBean constructor(@SerializedName("id") @ColumnInfo(name = "parent_id")var mId: Int)

资源表将包含以下列:resource_id，name，parent_id

resources table will have the following columns: resource_id, name, parent_id

来源: https://developer.android.com/training/data-storage/room/defining-data

注意:您无需在Kotlin中手动定义getter和setter.

Note: You don't need to manually define getter and setters in Kotlin.

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