當存儲對象類中使用了除String、Int 妻顶、Long等類型以外的復雜類型時候酸员，objectBox的處理方法：
實現(xiàn)一個objectBox的PropertyConverter接口的類，將復雜類型處轉(zhuǎn)換為基礎類型

實體類

import android.net.Uri
import com.zbb.mine.em.SourceFrom
import com.zbb.mine.em.SourceFromConverter
import io.objectbox.annotation.Convert
import io.objectbox.annotation.Entity
import io.objectbox.annotation.Id
import io.objectbox.relation.ToMany

@Entity
class MusicEntity() {
    //    @assignable 手動管理id
    @Id
    var id: Long = 0
    var name: String = ""
    var singer: String = "未知"
    var avatarUrl: String? = null
    var avatarPath: String? = null
    var url: String? = null
    var path: String? = null
    @Convert(converter = UriConverter::class, dbType = String::class)
    var uri: Uri? = null
    var lrcUrl: String? = null
    var lrcPath: String? = null
    var duration: Int = 0
    var fileSize: Long = 0
    var album: String? = null
    @Convert(converter = SourceFromConverter::class, dbType = Int::class)
    var from: SourceFrom = SourceFrom.UNKMOWN
    //    @Transient 不存放到數(shù)據(jù)庫
//    var xx
    lateinit var groups: ToMany<GroupEntity>
    override fun toString(): String {
        return "MusicEntity(id=$id, name='$name', singer='$singer', avatarUrl=$avatarUrl, avatarPath=$avatarPath, url=$url, path=$path, uri=$uri, lrcUrl=$lrcUrl, lrcPath=$lrcPath, duration=$duration, fileSize=$fileSize, album=$album, from=$from)"
    }
}

轉(zhuǎn)換處理類

import android.net.Uri
import io.objectbox.converter.PropertyConverter

class UriConverter : PropertyConverter<Uri, String> {
    override fun convertToDatabaseValue(entityProperty: Uri?): String {
        return entityProperty?.toString() ?: ""
    }

    override fun convertToEntityProperty(databaseValue: String?): Uri? {
        if (databaseValue == null) {
            return null
        } else {
            return Uri.parse(databaseValue)
        }
    }
}