简而言之，实际存储的数据相对复杂，通过 Db 浏览器手动输入可能很困难或令人沮丧。
例如考虑值是的单个条目：
data1 是 D1
数据2是A，B
data3 是 C,D,E
data4 是 F,G,H,I,J,K
data5 为 L,M,N,O
这实际上是使用 GSON 存储的，类似于（虽然不完全是）：-
但是，我认为您的代码存在问题。我相信，你不能有一个列（例如 data2）是一个列表/数组，该列必须是一个类（可能包含一个列表）。
- TypeConverters 似乎无法处理数组/列表。
你会得到一个编译器错误：-
error: Cannot figure out how to save this field into database. You can consider adding a type converter for it.
private final java.lang.String[] data2 = null;
^
所以为了演示（上面的数据来自哪里）创建了一个类来嵌入数组：-
data class StringArray(
var sa: Array<String>
)
那么你可以让数据成为：-
@Entity(tableName ="Data Table")
data class Datas(
@PrimaryKey(autoGenerate = true)
@ColumnInfo(name = "Id")
val id : Int,
@ColumnInfo(name = "Data1")
val data1 : String = "",
@ColumnInfo(name = "Data2")
var data2: StringArray,
@ColumnInfo(name = "Data3")
var data3 : StringArray,
@ColumnInfo(name = "Data4")
var data4 : StringArray,
@ColumnInfo(name = "Data5")
var data5 : StringArray
)
然后转换器类将/可能是：-
class converter {
@TypeConverter
fun fromString(value: String): List<String> {
val listType = object : TypeToken<ArrayList<String>>() {}.type
return Gson().fromJson(value, listType)
}
@TypeConverter
fun fromArrayList(list: List<String>): String {
return Gson().toJson(list)
}
/* Replacement Converters */
@TypeConverter
fun fromJSONStringToStringArray(value: String): StringArray {
val listType = object : TypeToken<StringArray>() {}.type
return Gson().fromJson(value,listType)
/* or just the single line :- that follows */
// return Gson().fromJson(value, StringArray::class.java)
}
@TypeConverter
fun fromStringArrayToJSONString(list: StringArray): String {
return Gson().toJson(list)
}
}
因此，您可以使用您的数据库（可能在不同的应用程序中纯粹用于生成数据）来实际创建数据库（这会更容易）或生成要复制并粘贴到 Db 中的数据浏览器正在做一些事情：-
对于演示，创建了一个 SourceData 类：-
/* The data to pre-populate the database */
class SourceData {
companion object {
val d1: Datas = Datas(
id = 0,
data1 = "D1",
data2 = StringArray(arrayOf("A","B")),
data3 = StringArray(arrayOf("C","D","E")),
data4 = StringArray(arrayOf("F","G","H","I","J","K")),
data5 = StringArray(arrayOf("L","M","N","O"))
)
val d2: Datas = Datas(
id = 0,
data1 = "D1",
data2 = StringArray(arrayOf("AA","AB","AC")),
data3 = StringArray(arrayOf("AD","AE")),
data4 = StringArray(arrayOf("AF","AG","AH","AI","AJ","AK")),
data5 = StringArray(arrayOf("AL","AM","AN","AO"))
)
val d3: Datas = Datas(
id = 0,
data1 = "D1",
data2 = StringArray(arrayOf("BA","BB","BC")),
data3 = StringArray(arrayOf("BD","BE")),
data4 = StringArray(arrayOf("BF","BG","BH","BI","BJ","BK")),
data5 = StringArray(arrayOf("BL","BM","BN","BO"))
)
val all: List<Datas> = listOf(d1,d2,d3)
}
}
- 不是最容易使用，但比尝试手动创建 JSON 更容易。
- 现在是 3 行数据。
插入的@Dao 类：-
@Dao
abstract class AllDao {
@Insert
abstract fun insert(datas: Datas): Long
@Insert
abstract fun insert(vararg datas: Datas): Array<Long>
@Insert
abstract fun insert(datasList: List<Datas>): Array<Long>
}
- 第一个将插入一行
- 第二个将插入 1 个或多个，例如
insert(d1,d2,d3)
- 第三个需要一个列表
您将需要一个包含 @TypeConverters 注释的 @Database 类，该注释指定转换器类，例如:-
@Database(entities = [Datas::class],version = 1)
@TypeConverters(converter::class)
abstract class TheDatabase: RoomDatabase() {
abstract fun getAllDao(): AllDao
companion object {
@Volatile
private var instance: TheDatabase? = null
fun getInstance(context: Context): TheDatabase {
if (instance == null) {
instance = Room.databaseBuilder(
context,
TheDatabase::class.java,
"my.db"
)
.allowMainThreadQueries()
.build()
}
return instance as TheDatabase
}
}
}
- 注意
allowMainThreadQueries 用于方便和简洁
最后是一个 Activity，在这种情况下，它使用 fromStringArrayToJSONString TypeConverter 输出 JSON，可以将其复制并粘贴到 DB 浏览器中，甚至可以重新调整以作为文件导入（我猜（我只是创建数据库并复制数据库文件））。
class MainActivity : AppCompatActivity() {
lateinit var db: TheDatabase
lateinit var dao: AllDao
override fun onCreate(savedInstanceState: Bundle?) {
super.onCreate(savedInstanceState)
setContentView(R.layout.activity_main)
db = TheDatabase.getInstance(this)
dao = db.getAllDao()
dao.insert(all)
logWhatConverterStores(d1)
logWhatConverterStores(d2)
logWhatConverterStores(d3)
}
}
fun logWhatConverterStores(d: Datas) {
logAD(d.data2)
logAD(d.data3)
logAD(d.data4)
logAD(d.data5)
}
private fun logAD(aD: StringArray) {
Log.d("CONVERTED","Converted/Stored as ${converter().fromStringArrayToJSONString(aD)}")
}
}
运行上述程序会生成一个数据库（通过 Android Studio 的 App Inspection）：-
日志中的一个：-
2021-09-26 21:23:40.002 Converted/Stored as {"sa":["A","B"]}
2021-09-26 21:23:40.003 Converted/Stored as {"sa":["C","D","E"]}
2021-09-26 21:23:40.007 Converted/Stored as {"sa":["F","G","H","I","J","K"]}
2021-09-26 21:23:40.008 Converted/Stored as {"sa":["L","M","N","O"]}
2021-09-26 21:23:40.010 Converted/Stored as {"sa":["AA","AB","AC"]}
2021-09-26 21:23:40.012 Converted/Stored as {"sa":["AD","AE"]}
2021-09-26 21:23:40.012 Converted/Stored as {"sa":["AF","AG","AH","AI","AJ","AK"]}
2021-09-26 21:23:40.014 Converted/Stored as {"sa":["AL","AM","AN","AO"]}
2021-09-26 21:23:40.015 Converted/Stored as {"sa":["BA","BB","BC"]}
2021-09-26 21:23:40.016 Converted/Stored as {"sa":["BD","BE"]}
2021-09-26 21:23:40.017 Converted/Stored as {"sa":["BF","BG","BH","BI","BJ","BK"]}
2021-09-26 21:23:40.017 Converted/Stored as {"sa":["BL","BM","BN","BO"]}