I am trying to use type converters in Android (Kotlin) so i am using the type converters class but i am getting confused like inside of the clouds i am having a single variable so i have returned it but
#Entity(tableName = "WeatherDb")
data class WeatherDTO(
val base: String,
val clouds: Clouds,
val cod: Int,
val coord: Coord,
val dt: Int,
#PrimaryKey(autoGenerate = true)
val id: Int,
val main: Main,
val name: String,
val sys: Sys,
val timezone: Int,
val visibility: Int,
val weather: List<Weather>,
val wind: Wind
)
class TypeConverters {
#TypeConverter
fun fromCloudsToDouble(clouds: Clouds): Int {
return clouds.all
}
fun fromCoordToDouble(coord: Coord): Double {
}
}
In coord class here are multiple with different datatypes how to covert this?
data class Main(
val feels_like: Double,
val grnd_level: Int,
val humidity: Int,
val pressure: Int,
val sea_level: Int,
val temp: Double,
val temp_max: Double,
val temp_min: Double
)
Clouds.kt
data class Clouds(
val all: Int
)
Coord.kt
data class Coord(
val lat: Double,
val lon: Double
)
Main.kt
data class Main(
val feels_like: Double,
val grnd_level: Int,
val humidity: Int,
val pressure: Int,
val sea_level: Int,
val temp: Double,
val temp_max: Double,
val temp_min: Double
)
Sys.kt
data class Sys(
val country: String,
val id: Int,
val sunrise: Int,
val sunset: Int,
val type: Int
)
Weather.kt
data class Weather(
val description: String,
val icon: String,
val id: Int,
val main: String
)
Wind.kt
data class Wind(
val deg: Int,
val gust: Double,
val speed: Double
)
WeatherViewModel.kt
#HiltViewModel
class WeatherViewModel #Inject constructor(
private val repo:WeatherRepository,
private val application: Application,
private val WeatherDb:WeatherDB,
private val fusedLocationProviderClient: FusedLocationProviderClient
) :ViewModel(){
private val _resp = MutableLiveData<WeatherDTO>()
val weatherResp:LiveData<WeatherDTO>
get() = _resp
private val _cord = MutableLiveData<Coord>()
val cord:LiveData<Coord>
get() = _cord
var locality:String = ""
fun getWeather(latitude:Double,longitude:Double) =
viewModelScope.launch {
repo.getWeather(latitude,longitude).let { response->
if(response.isSuccessful){
Log.d("response","${response.body()}")
WeatherDb.WeatherDao().insertWeather(response.body()!!)
_resp.postValue(response.body())
}else{
Log.d("Weather Error","getWeather Error Response: ${response.message()}")
}
}
}
fun fetchLocation():Boolean{
val task = fusedLocationProviderClient.lastLocation
if(ActivityCompat.checkSelfPermission(application,android.Manifest.permission.ACCESS_FINE_LOCATION)
!=PackageManager.PERMISSION_GRANTED &&
ActivityCompat.checkSelfPermission(application,android.Manifest.permission.ACCESS_COARSE_LOCATION)
!=PackageManager.PERMISSION_GRANTED
){
return true
}
task.addOnSuccessListener {
if(it!=null){
getWeather(it.latitude,it.longitude)
getAddressName(it.latitude,it.longitude)
Log.d("localityname", locality)
}
}
return true
}
private fun fetchLocationDetails(){
}
private fun getAddressName(lat:Double,long:Double):String{
var addressName = " "
val geoCoder = Geocoder(application, Locale.getDefault())
val address = geoCoder.getFromLocation(lat,long,1)
if (address != null) {
addressName = address[0].adminArea
}
locality = addressName
Log.d("subadmin",addressName.toString())
Log.d("Address", addressName)
return addressName
}
fun getCoordinates(cord:String){
val geocoder = Geocoder(application,Locale.getDefault())
val address = geocoder.getFromLocationName(cord,2)
val result = address?.get(0)
if (result != null) {
getWeather(result.latitude,result.longitude)
getAddressName(result.latitude,result.longitude)
}
}
}
Here is my converter in the Kotlin:
class Converters {
#TypeConverter
fun valueFromDomainToStorage(value: Value): String {
return value.convertToJson()
}
#TypeConverter
fun valueFromStorageToDomain(str: String): Value {
// we can not create an empty instance of value as TypeDecoder.java should call non-empty constructor
return Value(
"just a stub",
BigInteger.valueOf(0),
BigInteger.valueOf(0),
false,
BigInteger.valueOf(0)
)
.fromJson(str)
}
}
where .convertToJson() and .fromJson(str) implemented as extensions within Value class:
fun Value.convertToJson(): String {
val result = JSONObject()
result.put(ValueConst.OFFER_FIELD, offer)
result.put(ValueConst.AVAILABLE_SINCE, availableSince.toLong())
result.put(ValueConst.AVAILABLE_END, availabilityEnd.toLong())
result.put(ValueConst.IS_CONSUMED, isConsumed)
result.put(ValueConst.LOCKED_UNTIL, lockedUntil)
return result.toString()
}
fun Value.fromJson(json: String): Value {
val subj = JSONObject(json)
return Value(
subj.optString(ValueConst.OFFER_FIELD),
BigInteger.valueOf(subj.optLong(ValueConst.AVAILABLE_SINCE)),
BigInteger.valueOf(subj.optLong(ValueConst.AVAILABLE_END)),
subj.optBoolean(ValueConst.IS_CONSUMED),
BigInteger.valueOf(subj.optLong(ValueConst.LOCKED_UNTIL))
)
}
You should implement Converter class for each non-native class type. Do not forget to register your converters on database:
#Database(entities = [ChainTransaction::class], version = 1, exportSchema = false)
#TypeConverters(Converters::class)
abstract class AppDatabase: RoomDatabase() {
When you have compile the code and later introduce new changes, you have to increase version parameter too to make changes to take effect:
#Database(entities = [ChainTransaction::class], version = 2, exportSchema = false)
#TypeConverters(Converters::class)
abstract class AppDatabase: RoomDatabase() {
Here is official documentation and even training on this topic:
https://developer.android.com/training/data-storage/room
so i am using the type converters class but i am getting confused
SQLite (the database around which Room is an object orientated wrapper) is not an object orientated (or aware) database. It is a database that can store primitive types of data which are one of
INTEGER (such as Int or Long), REAL
REAL (such as Float or Double)
TEXT (such as String)
BLOB (such as ByteArray)
NULL
Therefore to store a type of Coord, Cloud or Weather .... you have three options:-
to embed the class, in which case the fields are copied from the embedded class (would be complicated if the embedded classes contained unsupported types). not covered in the answer
to have the class as a table in it's own right with a relationship between it and the parent (WeatherDTO). not covered in the answer
to convert the class to one of the SQLite types (of which either TEXT or BLOB would probably only be practical).
Considering option 3 (TyepConverters) converting the data is of little, if any, use just storing the data as you would not be able to retrieve the data.
As such type converters should always be paired.
One of the pair will be to convert from the class to a type that can be stored.
The other will be to convert from the stored type to the class.
As such you will need quite a few type Converters, that is 2 each for fields:-
clouds (class Clouds)
coord (class Coord)
main (class Main)
sys (class Sys)
weather (class List)
wind (class Wind)
It is the Class of the field that Room looks at to locate the respective type converter.
One of the simplest ways to convert objects (aka classes) is to convert the object to a JSON representation. Although a complexity with this is that there are many JSON libraries and they will often have differences.
For the examples that follow Googles JSON library has been used. However, use of this library with Room doesn't appear to directly support the use of List<the_class> e.g. List.
The dependency for this being (as an example) implementation 'com.google.code.gson:gson:2.10'
As a get around a new class WeatherList has ben used as per:-
data class WeatherList(
val weatherList: List<Weather>
)
and the WeatherDTO class has been changed to use it as per :-
....
//val weather: List<Weather>,
val weather: WeatherList,
....
As such the TypeConverters class could then be:-
class TypeConverters {
#TypeConverter
fun fromCloudsToJSONString(clouds: Clouds): String = Gson().toJson(clouds)
#TypeConverter
fun toCloudsFromJSONString(jsonString: String): Clouds = Gson().fromJson(jsonString,Clouds::class.java)
#TypeConverter
fun fromCoordToJSONString(coord: Coord): String = Gson().toJson(coord)
#TypeConverter
fun toCoordFromJSONString(jsonString: String): Coord = Gson().fromJson(jsonString,Coord::class.java)
#TypeConverter
fun fromMaintoJSONString(main: Main): String = Gson().toJson(main)
#TypeConverter
fun toMainFromJSONString(jsonString: String): Main = Gson().fromJson(jsonString,Main::class.java)
#TypeConverter
fun fromSysToJSONString(sys: Sys): String = Gson().toJson(sys)
#TypeConverter
fun toSysFromJSONString(jsonString: String): Sys = Gson().fromJson(jsonString,Sys::class.java)
#TypeConverter
fun fromWeatherListFromJSONString(weatherList: WeatherList): String = Gson().toJson(weatherList)
#TypeConverter
fun toWeatherListFromJSOnString(jsonString: String): WeatherList = Gson().fromJson(jsonString,WeatherList::class.java)
#TypeConverter
fun fromWindToJSONString(wind: Wind): String = Gson().toJson(wind)
#TypeConverter
fun toWindFromJSONString(jsonString: String): Wind = Gson().fromJson(jsonString,Wind::class.java)
}
As such the all the types/classes/objects that are not directly supported are converted to/from a JSON string representation of the type/class/object.
Note that you need to add the #TypeConverters(#TypeConverters( value = [<????>.TypeConverters::class]). Where has to distinguish between your projects TypeConverters class from Room's (TypeConverters is probably not the best name for the class, renaming it, would overcome the need to distinguish)
Working Example
The following puts the above into action.
As the question does not include the underlying classes, the following have been used:-
data class Coord(
val longitude: Double,
val latitude: Double
)
data class Clouds(
val cover: Double,
val type: String
)
data class Main(
val main: Double
)
data class Sys(
val sys: Double
)
data class WeatherList(
val weatherList: List<Weather>
)
data class Weather(
val weather: Double
)
data class Wind(
val wind: Double
)
The #Dao annotated interface was also made up and is simply:-
#Dao
interface AllDao {
#Insert(onConflict = OnConflictStrategy.IGNORE)
fun insert(weatherDTO: WeatherDTO)
#Query("SELECT * FROM weatherdb")
fun getAllFromWeatherDB(): List<WeatherDTO>
}
Also the #Database annotated abstract class was made up it being:-
#TypeConverters( value = [a.a.so74384736typeconverterconfusion.TypeConverters::class])
#Database(entities = [WeatherDTO::class], exportSchema = false, version = 1)
abstract class TheDatabase: RoomDatabase() {
abstract fun getAllDao(): AllDao
companion object {
private var instance: TheDatabase? = null
fun getInstance(context: Context): TheDatabase {
if (instance==null) {
instance = Room.databaseBuilder(context,TheDatabase::class.java,"the_database.db")
.allowMainThreadQueries()
.build()
}
return instance as TheDatabase
}
}
}
Note the package name used to distinguish the TypeConverters class from Room's TypeConverters class
the package name cannot be used elsewhere, so if the above is copied then it would have to be changed. There is no expectation that the code in it's entirety would be copied and used. The code is designed solely to demonstrate the TypeConverters.
Last some activity code to actually do something (store and retrieve some data):-
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(
WeatherDTO(
"base001",
Clouds(25.5,"cumulus"),10,
Coord(10.567,30.345),
11,
12,
Main(12345.67890),
"thename",
Sys(9.87654321),
14,
1000,
WeatherList(listOf(Weather(5.1234),Weather(6.5432), Weather(7.6543))),
Wind(23.12)
)
)
for (wdto in dao.getAllFromWeatherDB()) {
Log.d("DBINFO","base = ${wdto.base} longitude = ${wdto.coord.longitude} latitude = ${wdto.coord.latitude} etc ....")
}
}
}
RESULT
When run the log contains, as expected:-
D/DBINFO: base = base001 longitude = 10.567 latitude = 30.345 etc ....
Using App Inspection then the database looks like:-
The fields converted to a JSON string have been highlighted.
Obviously the data will very likely not exactly be as you would expect due to the made up classes.
Follow on from the previous answer #Embedded versus Type Converters
As can be seen from the previous answer, there are some issues in regard to using TypeConverters. From a database perspective the TypeConverters will inevitably contain bloat/unecessary data which is contrary to normalisation (not needlessly storing repetitive data).
As an example the JSON representation will for every row contain exactly the same the field names wasting storage, all rows will have the additional overhead of storing the delimiters ([s and ]s, {s and }s, :s ,s). Furthermore actually using the stored data can become complex due to the bloat and also due to multiple values being stored in a single column and as such can be restrictive.
It would be more efficient to not store the bloat and it could eliminate complexities and enhance the usability of the stored data from a database perspective (querying the data for retrieval) to not store multiple values in a single column.
Using the #Embedded annotation can very easily eliminate the bloat. Consider the following (an alternative version of the WeatherDTO class/entity):-
#Entity(tableName = "WeatherDbAlternative1")
data class WeatherDTOAlternative1(
val base: String,
#Embedded
val clouds: Clouds,
val cod: Int,
#Embedded
val coord: Coord,
val dt: Int,
#PrimaryKey(autoGenerate = true)
val id: Int,
#Embedded
val main: Main,
val name: String,
#Embedded
val sys: Sys,
val timezone: Int,
val visibility: Int,
//val weather: List<Weather>,
/* Unable to embed directly so not embedding */
val weather: WeatherList,
#Embedded
val wind: Wind
)
Bar the weather field all that has been done is add the #Embedded annotation. Noting that the classes of the fields all have fields of types directly supported by Room.
Adding this entity to the #Database annotation and adding a couple of additional functions in the #Dao annotated class as per:-
#Query("SELECT * FROM weatherdbalternative1")
fun getAllFromWeatherDBAlternative1(): List<WeatherDTOAlternative1>
#Insert(onConflict = OnConflictStrategy.IGNORE)
fun insert(weatherDTOAlternative1: WeatherDTOAlternative1)
And then amending the Activity code to include :-
/*ALTERNATIVE 1 All but WeatherList embedded */
dao.insert(
WeatherDTOAlternative1(
"base001A",
Clouds(25.5, "cumulus"),
10,
Coord(10.567, 30.345),
11,
12,
Main(12345.67890),
"thenameA1",
Sys(9.87654321),
14,
1000,
WeatherList(listOf(Weather(5.1234), Weather(6.5432), Weather(7.6543))),
Wind(23.12)
)
)
for (wdto in dao.getAllFromWeatherDBAlternative1()) {
Log.d(
"DBINFO",
"base = ${wdto.base} longitude = ${wdto.coord.longitude} latitude = ${wdto.coord.latitude} etc ...."
)
}
Now results in the Log including:-
D/DBINFO: base = base001 longitude = 10.567 latitude = 30.345 etc ....
D/DBINFO: base = base001A longitude = 10.567 latitude = 30.345 etc ....
i.e. effectively the same data is stored and retrievable
However the data is now stored in the database as (ignoring the weather field) as :-
i.e. the data stored is much cleaner but at the expense of additional columns (which can be advantageous).
additionally although not apparent, the fields that have the #Embedded annotation do not need the TypeConverters.
error: Cannot find getter for field.
private final com.kbb.webviewolacakmi.model.content icerik = null;
I didn't manage to add the subparts of the json to the room.
Thanks to everyone who helped.
I would be very happy if you could write a clear code example.
Json File :
{
"date": "xxx",
"title": {
"rendered": "Title"
},
"content": {
"rendered": "content",
"protected": false
},
}
Data Class :
#Entity
data class Icerik(
#ColumnInfo(name="title")
#SerializedName("title")
val baslik:title?,
#ColumnInfo(name="content")
#SerializedName("content")
public val icerik:content?,
#ColumnInfo(name="date")
#SerializedName("date")
val tarih:String?,
#ColumnInfo(name="jetpack_featured_media_url")
#SerializedName("jetpack_featured_media_url")
val gorsel:String?,) {
#PrimaryKey(autoGenerate = true)
var uuid:Int=0
fun getIcerik(){
}
}
data class content(
#ColumnInfo(name="rendered")
#SerializedName("rendered")
public val content: String?,
#ColumnInfo(name="protected")
#SerializedName("protected")
val bool: Boolean?,
){
#PrimaryKey(autoGenerate = true)
var uuid:Int=0
}
data class title(
#ColumnInfo(name="rendered")
#SerializedName("rendered")
val ytitle:String?
){
#PrimaryKey(autoGenerate = true)
var uuid:Int=0
}
IcerikDatabase Class
#TypeConverters(value = [RoomTypeConverters::class])
#Database(entities = arrayOf(Icerik::class), version = 1)
abstract class IcerikDatabase:RoomDatabase() {
abstract fun icerikDao(): IcerikDAO
companion object {
#Volatile private var instance:IcerikDatabase? = null
private val lock=Any()
operator fun invoke(context: Context)= instance?: synchronized(lock){
instance?: databaseOlustur(context).also {
instance=it
}
}
private fun databaseOlustur(context: Context) = Room.databaseBuilder(
context.applicationContext, IcerikDatabase::class.java,
"icerikdatabase"
).build()
}
}
IcerikDao
interface IcerikDAO {
#Insert
suspend fun instertAll(vararg icerik:Icerik):List<Long>
#Query("SELECT * FROM icerik")
suspend fun getAllIcerik():List<Icerik>
#Query("SELECT * FROM icerik WHERE uuid=:icerikId ")
suspend fun getIcerik(icerikId:Int):Icerik
#Query("DELETE FROM icerik")
suspend fun deleteAllIcerik()
}
TypeConverter
class RoomTypeConverters {
#TypeConverter
fun fromTitleToJSONString(title: title?): String? {
return Gson().toJson(title)
}
#TypeConverter
fun toTitleFromJSONString(jsonString: String?): title? {
return Gson().fromJson(jsonString, title::class.java)
}
#TypeConverter
fun fromIcerikToJSONString(content: content?): String? {
return Gson().toJson(content)
}
#TypeConverter
fun toIcrerikFromJSONString(jsonString: String?): content? {
return Gson().fromJson(jsonString, content::class.java)
}
}
I believe that your issue is in regard, not to room, but with the JSON handling.
The JSON file that you have shown cannot directly build an Icerik object.
Rather you need to have an intermediate class that can be built with the JSON and then use that intermediate class to then build the IceRik object.
So you want an intermediate class something along the lines of:-
data class JsonIceRik(
val content: content,
val title: title,
val date: String
)
If the JSON is then amended to be:-
val myjson = "{\"date\": \"xxx\",\"title\": {\"rendered\": \"Title\"},\"content\": {\"rendered\": \"content\",\"protected\": false}}"
note the omission of the comma between the two closing braces
Then you could use:-
val m5 = Gson().fromJson(myjson,JsonIceRik::class.java)
To build the intermediate JsonIceRik object.
And then you could use:-
val i5 = Icerik(baslik = m5.title, icerik = m5.content, tarih = m5.date,gorsel = "whatever")
To build the Icerik from the intermediate JsonIceRik.
The result in the database would be:-
uuid in the title and content serve no purpose and will always be 0 if obtaining the data from JSON
the #PrimaryKey annotation only serves to introduce warnings -
A Table can only have 1 Primary Key ( a composite Primary Key can include multiple columns though (but you cannot use the #PrimaryKey annotation, you have to instead use the primarykeys parameter of the #Entity annotation) )
You might as well have :-
data class content(
#ColumnInfo(name="rendered")
#SerializedName("rendered")
val content: String?,
#ColumnInfo(name="protected")
#SerializedName("protected")
val bool: Boolean?,
)
data class title(
#ColumnInfo(name="rendered")
#SerializedName("rendered")
val ytitle:String?
)
Otherwise, as you can see, the data according to the JSON has been correctly stored.
I've got a TypeConverter class linked to my database, but it doesn't seem to be getting called and therefore i'm getting the following error
ForecastAQSpecified.java:9: error: Cannot figure out how to read this field from a cursor.
private final java.time.LocalDate dt = null;
dt is the datetime I get in my JSON response in the form of an epoch Int. I'm looking to convert this to a LocalDate. My Entity class is as follows
#Entity(tableName = "future_AQ", indices = [Index(value = ["dt"], unique = true)])
data class ForecastAQ(
#PrimaryKey(autoGenerate = true)
val id: Int? = null,
#Embedded
val components: Components,
val dt: Int,
#Embedded
val main: Main
)
val dt: Int is the what I am looking to convert. My TypeConverter class is as follows
object DateConverter {
#TypeConverter
#JvmStatic
fun stringToDate(str: String?) = str?.let {
LocalDate.parse(it, DateTimeFormatter.ISO_LOCAL_DATE)
}
#TypeConverter
#JvmStatic
fun dateToString(localDate: LocalDate?) = localDate?.format(
DateTimeFormatter.ISO_LOCAL_DATE
)
#TypeConverter
#JvmStatic
fun timestampToDateTime(dt : Int?): LocalDate? {
try {
val sdf = SimpleDateFormat("yyyy-MM-dd'T'hh:mm:ss")
val netDate = dt?.times(1000L)?.let { Date(it) }
val sdf2 = sdf.format(netDate)
return LocalDate.parse(sdf2, DateTimeFormatter.ISO_LOCAL_DATE_TIME)
Log.d("TAG", "date " + LocalDate.parse(sdf2, DateTimeFormatter.ISO_LOCAL_DATE_TIME).toString());
} catch (e : Exception) {
return null
e.printStackTrace()
}
}
The first two are required in another part of the database where I receive the date response as a String. They are getting called just fine. My The final one is not however - and this is the one I need to convert the Int to a DateTime object
The database class is as follows for reference
#Database(
entities = [CurrentConditions::class, ConditionsLocation::class, ForecastWeather::class, ForecastAQ::class],
version = 1
)
#TypeConverters(DateConverter::class)
abstract class ConditionsDatabase : RoomDatabase() {
abstract fun getCurrentConditionsDAO() : CurrentConditionsDAO
abstract fun getConditionsLocationDAO() : ConditionsLocationDAO
abstract fun getForecastWeatherDAO() : ForecastWeatherDAO
abstract fun getForecastAirQualDAO() : ForecastAqDAO
companion object{
#Volatile private var instance: ConditionsDatabase? = null
private val LOCK = Any()
operator fun invoke(context: Context) = instance ?: synchronized(LOCK) {
instance ?: buildDatabase(context).also {
instance = it
}
}
private fun buildDatabase(context: Context) =
Room.databaseBuilder(context.applicationContext,
ConditionsDatabase::class.java, CURRENT_CONDITIONS_DATABASE_NAME)
.build()
}
}
Many thanks
You should create a class instead of object
replace
object DateConverter {
to
class DateConverter {
remove JvmStatic annotation
I have POJO data classes from API.
#Entity(tableName = "pokemon")
class Pokemon(
#PrimaryKey(autoGenerate = true)
var id: Int? = null,
#SerializedName("count")
#Expose
val count: Int?,
#SerializedName("next")
#Expose
val next: String?,
#SerializedName("results")
#Expose
val results: List<Result>? = null
)
And class List:
class Result(
#SerializedName("name")
#Expose
val name: String?,
#SerializedName("url")
#Expose
val url: String?
)
My database class:
#Database(entities = [Pokemon::class], version = 1, exportSchema = false)
#TypeConverters(Converters::class)
abstract class AppDatabase : RoomDatabase() {
companion object {
private var db: AppDatabase? = null
private const val DB_NAME = "main.db"
private val LOCK = Any()
fun getInstance(context: Context): AppDatabase {
synchronized(LOCK) {
db?.let { return it }
val instance = Room.databaseBuilder(
context,
AppDatabase::class.java,
DB_NAME
)
.fallbackToDestructiveMigration()
.build()
db = instance
return instance
}
}
}
abstract fun PokemonDao(): PokemonDao
}
My class Converters:
class Converters {
#TypeConverters
fun fromResultToString(result: slode.elsloude.pokemonapi.pojo.Result?): String? {
return Gson().toJson(result)
}
#TypeConverters
fun fromStringToResult(value: String?): slode.elsloude.pokemonapi.pojo.Result? {
return Gson().fromJson(value, Result::class.java)
}
}
The error I get when attempting this is:
error: Class is referenced as a converter but it does not have any converter methods. - androidx.databinding.adapters.ConvertersC:\Users\elslode\.AndroidStudio3.6\PokemonApi\app\build\tmp\kapt3\stubs\debug\slode\elsloude\pokemonapi\pojo\Pokemon.java:22: error: Cannot figure out how to save this field into database. You can consider adding a type converter for it.
private final java.util.List<slode.elsloude.pokemonapi.pojo.Result> results = null;
^C:\Users\elslode\.AndroidStudio3.6\PokemonApi\app\build\tmp\kapt3\stubs\debug\slode\elsloude\pokemonapi\pojo\SinglePokemon.java:14: error: Cannot figure out how to read this field from a cursor.
The #TypeConverters annotation is used to link your converters with the database, as yuo have done here:
#TypeConverters(Converters::class)
However when declaring a converter method you should be using the #TypeConverter annotation:
class Converters {
#TypeConverter
fun fromResultToString(result: slode.elsloude.pokemonapi.pojo.Result?): String? {
return Gson().toJson(result)
}
#TypeConverter
fun fromStringToResult(value: String?): slode.elsloude.pokemonapi.pojo.Result? {
return Gson().fromJson(value, Result::class.java)
}
}
Note the plural on #TypeConverters vs #TypeConverter.
Secondly Room cannot automatically infer a list conversion for you, so the type converter functions will have to map the full List<Result> to a String and vice versa.
I am using okhttp to fetch Json data from an API, casting it into Gson for some other purposes, and at the same time, storing of the API data into a Room Database. (It can be storing of the API json data itself, or the casted Gson version) However, I am unsuccessful in this, and hope you could point me to the direction where I am going wrong.
I think i'm missing a typeConverter to convert the data retrieved from API and casted into GSON, to be stored in the Room database. But i'm not sure if i'm correct in this, or if my approach is correct in the first place.
Or could it be an issue with the fact that I have an Entities data class, but gsonData is casted into SampleData data class?
DataGetter
...
...
...
// this suspend function is run within a coroutine.
private suspend fun APICall(url: String, pageNumber: Int, context: Context){
val urlRequest = Request.Builder().url(url).build() // Building of the URL to fetch data
httpClient.newCall(urlRequest).enqueue(object : Callback {
// onFailure -> cutting this out to shorten code
// onResponse is where I am fetching the data and calling put to DB
override fun onResponse(call: Call, response: Response) {
val dataString = response.body!!.string()
val gsonData = gsonResult.fromJson(dataString, SampleData::class.java)
// Do some other stuffs with gsonData separately. This doesn't return anything to gsonData.
putToRoomDb(gsonData, context) // This will eventually be done via another coroutine.
}
}
}
private suspend fun putToRoomDb(sampleData: SampleData, context: Context) {
val db = MyOnlyDatabase.getInstance(context)
db.MyOnlyDao().updateOrInsert(sampleData)
}
Entity
#Entity(tableName = "sample_data_code_names")
data class SampleDataEntities(
#PrimaryKey
var Code: Int,
val Name: String,
val Description: String,
val Item1: String,
val Item2: String
)
Dao
#Dao
interface SampleDataDao {
#Insert(onConflict = OnConflictStrategy.REPLACE)
suspend fun updateOrInsert(sampleDataEntities: SampleDataEntities)
}
Database
#Database(entities = [SampleDataEntities::class], version = 1, exportSchema = false)
abstract class MyOnlyDatabase: RoomDatabase() {
abstract fun sampleDataDao(): SampleDataDao
companion object {
#Volatile
private var instance: MyOnlyDatabase? = null
fun getInstance(context: Context): MyOnlyDatabase{
return instance ?: synchronized(this) {
instance ?: buildDatabase(context).also { instance = it }
}
}
private fun buildDatabase(context: Context): MyOnlyDatabase{
return Room.databaseBuilder(context, MyOnlyDatabase::class.java, "MyOnlyDatabase.db")
.fallbackToDestructiveMigration()
.build()
}
}
}
Note: Below is the data class for which gsonData is casted into.
data class SampleData(val value: List<SampleDataInfoItems>)
data class SampleDataInfoItems(
val Code: String,
val Name: String,
val Description: String,
val Item1: BigDecimal,
val Item2: BigDecimal
)
You are not annotating your fields according to the JSON response that is coming from the server.
data class SampleDataInfoItems(
#SerializedName("name_this_field_on_json")
val Code: String,
#SerializedName("and_so_on_for_all_fields")
val Name: String,
val Description: String,
val Item1: BigDecimal,
val Item2: BigDecimal
)
Also I think you need the GsonConververFactory for Retrofit.