I'm trying to convert my Parcel Creator code from Java to Kotlin. The auto code converter fails at this and I'm not sure how to resolve it. The code I'm converting is:
public static final Creator<Save> CREATOR = new Creator<Save>() {
#Override
public Save[] newArray(int size) {
return new Save[size];
}
#Override
public Save createFromParcel(Parcel incoming) {
return new Save(incoming);
}
};
I end up with this:
val CREATOR: Parcelable.Creator<Save> = object : Parcelable.Creator<Save> {
override fun newArray(size: Int): Array<Save> {
return arrayOfNulls(size)
}
override fun createFromParcel(incoming: Parcel): Save {
return Save(incoming)
}
}
which gives an error saying 'Type inference failed' for arrayOfNulls(size). I have tried changing it to Save(size) but that doesn't work either. Any Ideas?
arrayOfNulls will return an array of nullable elements, Array<Save?> in this case. You should change your function's return type to match that.
override fun newArray(size: Int): Array<Save?> {
return arrayOfNulls(size)
}
You can try this plugin to do Parcelable, just suggestion, I never tried but come across while googling.
Related
I am learning Kotlin, and not know it properly. I have a piece of code in Java:
private static Signature[] createSignatures(String... encodedSignatures) {
return Arrays.stream(encodedSignatures)
.map(encodedSignature -> new Signature(Base64.decode(encodedSignature, Base64.DEFAULT)))
.toArray(Signature[]::new);
}
I want to convert it to Kotlin, and I have reached till here:
private static Signature[] createSignatures(String... encodedSignatures) {
return Arrays.stream(encodedSignatures)
.map(encodedSignature -> new Signature(Base64.decode(encodedSignature, Base64.DEFAULT)))
.toArray(Signature[]::new);
}
But the above doesn't work, especially the line at the end, that is, .toArray(Signature[]::new) is the problem. How do I solve it? What is the correct way to convert streams to array in kotlin?
You can achieve your goal by using following code:
private fun createSignatures(vararg encodedSignatures: String): Array<Signature> {
return encodedSignatures
.map { Signature(Base64.decode(it, Base64.DEFAULT)) }
.toTypedArray()
}
Try this:
private fun createSignatures(vararg encodedSignatures: String): Array<Signature?>? {
return Arrays.stream(encodedSignatures)
.map { encodedSignature -> Signature(Base64.decode(encodedSignature, Base64.DEFAULT)) }
.toArray { _Dummy_.__Array__() }
}
Trying to implement a custom JSONB binding that maps to an object containing a map. Generated code throws a None of the following functions can be called with the arguments supplied error caused by the following line:
val SOME_FIELD: TableField<SomeRecord, Jsonb?> = createField(DSL.name("meta"), SQLDataType.JSONB.nullable(false).defaultValue(DSL.field("'{}'::jsonb", SQLDataType.JSONB)), this, "", JsonbBinding())
Here's my configuration:
class JsonbBinding : Binding<Any, Jsonb> {
private val mapper = ObjectMapper()
override fun converter(): Converter<Any, Jsonb> {
return object : Converter<Any, Jsonb> {
override fun from(dbObject: Any?): Jsonb {
if (dbObject == null) return Jsonb()
val props = mapper.readValue<MutableMap<String, Any>>(dbObject.toString())
return Jsonb(props)
}
override fun to(userObject: Jsonb?): Any? {
return mapper.writeValueAsString(userObject)
}
override fun fromType(): Class<Any> {
return Any::class.java
}
override fun toType(): Class<Jsonb> {
return Jsonb::class.java
}
}
}
override fun sql(ctx: BindingSQLContext<Jsonb>) {
ctx.render()?.let {
if (it.paramType() == ParamType.INLINED) {
it.visit(
DSL.inline(ctx.convert(converter()).value())
).sql("::jsonb")
} else {
it.sql("?::jsonb")
}
}
}
override fun register(ctx: BindingRegisterContext<Jsonb>) {
ctx.statement().registerOutParameter(ctx.index(), Types.VARCHAR)
}
override fun set(ctx: BindingSetStatementContext<Jsonb>) {
ctx.statement().setString(
ctx.index(),
ctx.convert(converter()).value()?.toString()
)
}
override fun set(ctx: BindingSetSQLOutputContext<Jsonb>) {
throw SQLFeatureNotSupportedException()
}
override fun get(ctx: BindingGetResultSetContext<Jsonb>) {
ctx.convert(converter()).value(ctx.resultSet().getString(ctx.index()))
}
override fun get(ctx: BindingGetStatementContext<Jsonb>) {
ctx.convert(converter()).value(ctx.statement().getString(ctx.index()))
}
override fun get(ctx: BindingGetSQLInputContext<Jsonb>) {
throw SQLFeatureNotSupportedException()
}
}
<forcedType>
<userType>org.example.Jsonb</userType>
<binding>org.example.JsonbBinding</binding>
<includeExpression>.*</includeExpression>
<includeTypes>jsonb</includeTypes>
</forcedType>
Also, it seems like the line causing problems is mapping database data to JOOQ's default JSONB object. Is that what's causing the issue? Is there anything I may want to do about it? Is there some other way of doing mapping database JSONB data to a map by JOOQ?
I think you're confusing the type variables on Binding<T, U> here:
T is the database / JDBC type (in this case org.jooq.JSONB)
U is the user type (in this case Any)
You have to implement the binding the other way round: Binding<JSONB?, Any?>. Since jOOQ already takes care of properly binding the JSONB type to JDBC, you can probably do with your Converter<JSONB?, Any?> implementation alone, and attach that to your generated code instead:
class JsonbConverter : Converter<JSONB?, Any?> { ... }
Also, you don't have to use your own Jsonb type to wrap JSON data here.
I'm quite new to Kotlin and I'd like to see if using high-order functions can help in my case.
My use-case is that I need to call the methods of an IInterface derived class to send events to one or more components. And I'd like to make this generic, and I want to check if a high-order funtion can help. A sample of code will help to understand (well, I hope so!).
private val eventListeners = mutableListOf<IEventInterface>() // List filled somewhere else!
private fun sendConnectionEvent(dummyString: String) {
val deadListeners = mutableListOf<IEventInterface>()
eventListeners.forEach {
try {
it.onConnectionEvent(dummyString)
} catch (e: DeadObjectException) {
Log.d(TAG, "Removing listener - Exception ${e.message}")
deadListeners.add(it)
}
}
deadListeners.forEach { it ->
eventListeners.remove(it)
}
}
private fun sendWonderfulEvent(dummyString: String, dummyInt: Int) {
val deadListeners = mutableListOf<IEventInterface>()
eventListeners.forEach {
try {
it.onWonderfulEvent(dummyString, dummyInt)
} catch (e: DeadObjectException) {
Log.d(TAG, "Removing listener - Exception ${e.message}")
deadListeners.add(it)
}
}
deadListeners.forEach { it ->
eventListeners.remove(it)
}
}
I added 2 similar methods (I will have many more in the real use case) and I think (I hope!) that something could be done but I can't make high-order function works in this case because:
I want to call the same method on several instances, and not 'just' a basic function
To make things even worse, the methods I need to call don't have the same prototype (that would have been too easy!).
Hope this is clear enough.
Thanks for your help!
VR
Here is how it can be done
fun onEvent(body: (IEventInterface) -> Unit) {
val deadListeners = mutableListOf<IEventInterface>()
eventListeners.forEach {
try {
body(it)
} catch (ex: DeadObjectException) {
Log.d(TAG, "Removing listener - Exception ${e.message}")
deadListeners.add(it)
}
}
deadListeners.forEach { it ->
eventListeners.remove(it)
}
}
Supposing an interface like this:
interface IEventInterface {
fun onConnectionEvent(dummyString: String)
fun onWonderfulEvent(dummyString: String, dummyInt: Int)
}
Define an generic type that implements your defined interface ( <T : IEventInterface>)
Define an mutable list of this type to receive your implementation (MutableList<T>.removeIfThrows)
Expect an extension function for you type that will do your specific validation (and custom parameters if you want)
Using an apply and returning the instance you can run your code like a pipeline
Executing the custom validation when you want
private fun <T : IEventInterface> MutableList<T>.removeIfThrows(validation: T.() -> Unit, customLogMessage: String? = null): MutableList<T> {
return apply {
removeIf {
it.runCatching {
validation()
}.onFailure { error ->
print(customLogMessage ?: "Removing listener - Exception ${error.message}")
}.isFailure
}
}
}
Define your specific implementation passing just the function with custom validation as an parameter
private fun <T : IEventInterface> MutableList<T>.sendConnectionEvent(dummyString: String) = removeIfThrows({
onConnectionEvent(dummyString)
})
private fun <T : IEventInterface> MutableList<T>.sendWonderfulEvent(dummyString: String, dummyInt: Int) = removeIfThrows({
onWonderfulEvent(dummyString, dummyInt)
})
Now you can run your code like an pipeline modifying your original object like this
private fun nowYouCanDoSomethingLikeThis() {
eventListeners
.sendConnectionEvent("some dummy string")
.sendWonderfulEvent("some another dummy string", 123)
}
First, I would like to ask you, if you think that this question deserves -1, be honest enough and please explain why.
This is the code for Application class:
class WeatherApp: Application() {
override fun onCreate() {
super.onCreate()
Realm.init(this)
Realm.setDefaultConfiguration(
RealmConfiguration.Builder()
.deleteRealmIfMigrationNeeded()
.initialData(DatabaseInitTransaction(applicationContext))
.build()
)
}
}
This is the transaction class:
class DatabaseInitTransaction(private val applicationContext: Context): Realm.Transaction {
override fun execute(realm: Realm) {
Log.d("DatabaseInitTransaction", "execute called.")
val cityDao = CityDao(realm)
realm.deleteAll()
var stream :InputStream? = null
try {
stream = applicationContext.assets.open("city.list.json")
cityDao.createAllFromJson(CityEntity::class.java, stream)
} catch (thr: Throwable) {
} finally {
stream?.close()
}
}
}
So, on cold start method execute() of DatabaseInitTransaction class is never get called. I could not figure out why, please, help!
You must check first your Custom Applicatiom Class name is written in Manifest file.
in
<Application>
tag with Class name
When implementing a twitter4j.StatusListner in Kotlin, I get the following IllegalAccessError and associated stack trace:
Exception in thread "main" java.lang.IllegalAccessError: tried to access class twitter4j.StreamListener from class rxkotlin.rxextensions.TwitterExampleKt$observe$1
at rxkotlin.rxextensions.TwitterExampleKt$observe$1.subscribe(TwitterExample.kt:50)
at io.reactivex.internal.operators.observable.ObservableCreate.subscribeActual(ObservableCreate.java:40)
at io.reactivex.Observable.subscribe(Observable.java:10700)
at io.reactivex.Observable.subscribe(Observable.java:10686)
at io.reactivex.Observable.subscribe(Observable.java:10615)
at rxkotlin.rxextensions.TwitterExampleKt.main(TwitterExample.kt:8)
Produced by the following code:
val twitterStream = TwitterStreamFactory().instance
// See https://stackoverflow.com/questions/37672023/how-to-create-an-instance-of-anonymous-interface-in-kotlin/37672334
twitterStream.addListener(object : StatusListener {
override fun onStatus(status: Status?) {
if (emitter.isDisposed) {
twitterStream.shutdown()
} else {
emitter.onNext(status)
}
}
override fun onException(e: Exception?) {
if (emitter.isDisposed) {
twitterStream.shutdown()
} else {
emitter.onError(e)
}
}
// Other overrides.
})
emitter.setCancellable { twitterStream::shutdown }
If I don't use Rx, it makes the exception a bit simpler:
twitterStream.addListener(object: twitter4j.StatusListener {
override fun onStatus(status: Status) { println("Status: {$status}") }
override fun onException(ex: Exception) { println("Error callback: $ex") }
// Other overrides.
})
Exception in thread "main" java.lang.IllegalAccessError: tried to access class twitter4j.StreamListener from class rxkotlin.rxextensions.TwitterExampleKt
at rxkotlin.rxextensions.TwitterExampleKt.main(TwitterExample.kt:14)
However, if I implement a Java wrapper function, no error is thrown and the behaviour is as expected:
Wrapper -
public class Twitter4JHelper {
public static void addStatusListner(TwitterStream stream, StatusListener listner) {
stream.addListener(listner);
}
}
Revised implementation -
val twitterStream = TwitterStreamFactory().instance
val listner = object: StatusListener {
override fun onStatus(status: Status?) {
if (emitter.isDisposed) {
twitterStream.shutdown()
} else {
emitter.onNext(status)
}
}
override fun onException(e: Exception?) {
if (emitter.isDisposed) {
twitterStream.shutdown()
} else {
emitter.onError(e)
}
}
// Other overrides.
}
Twitter4JHelper.addStatusListner(twitterStream, listner)
emitter.setCancellable { twitterStream::shutdown }
This revised solution comes from a blog post, which I think tries to explain the cause but Google translate is not being my friend. What is causing the IllegalAccessError? Is there a purely Kotlin based solution, or will I have to live with this workaround?
Yep that's not going to work.
addListener method takes a StreamListener param and StreamListener is non-public (package private). I would definitely raise a bug against Kotlin compiler for this.
The code Kotlin compiler generates is:
TwitterStream twitterStream = (new TwitterStreamFactory()).getInstance();
twitterStream.addListener((StreamListener)(new StatusListener() {
// ..overrides ...
}));
StatusListener already implements StreamListener so I don't see why the cast is required.
I worked around this by using a java utility class:
public class T4JCompat {
public static void addStatusListener(TwitterStream stream, StatusListener listener) {
stream.addListener(listener);
}
public static void removeStatusListener(TwitterStream stream, StatusListener listener) {
stream.removeListener(listener);
}
}
You can call these methods from Kotlin and things work as expected.