Migrate to the new kotlin-parcelize

Question

Can anyone please explain how to migrate to the new kotlin-parcelize?

I tried:

1. Replace apply plugin: 'kotlin-android-extensions' with apply plugin: 'kotlin-parcelize' in app build.gradle
2. Replace import kotlinx.android.parcel.Parcelize with import kotlinx.parcelize.Parcelize

The latter one leads to

Class 'ParcelZonedDateTime' is not abstract and does not implement abstract member public abstract fun describeContents(): Int defined in android.os.Parcelable

on e.g. this code:

import androidx.annotation.Keep
import kotlinx.parcelize.Parcelize
import org.threeten.bp.ZonedDateTime

@Keep
@Parcelize
data class ParcelZonedDateTime(var value: ZonedDateTime?) :Parcelable {
    override fun toString(): String {
        return value.toString()
    }
}

So, how to migrate to the new kotlin-parcelize?

Update:

Based on comments: Yes, I am on Kotlin 1.4.20 (which is newer than 1.4.20-M2).Kyzer is right that the error in the IDE (is not abstract and does not implement abstract member public abstract fun describeContents()) can and has to be ignored. Yet I have an issue where I use Generics:

import android.os.Parcelable
import kotlinx.parcelize.Parcelize

sealed class MyDialogEvent {
    @Parcelize
    data class Confirmed<T: Parcelable>(val identity: String, val data: T) : Parcelable
}

The generated code for this is

@kotlin.Metadata(mv = {1, 4, 1}, bv = {1, 0, 3}, k = 3)
public static final class Creator implements android.os.Parcelable.Creator<com.example.stackoverflow.MyDialogEvent.Confirmed> {
    
    public Creator() {
        super();
    }
    
    @org.jetbrains.annotations.NotNull()
    @java.lang.Override()
    public final com.example.stackoverflow.MyDialogEvent.Confirmed<T>[] newArray(int size) {
        return null;
    }
    
    @org.jetbrains.annotations.NotNull()
    @java.lang.Override()
    public final com.example.stackoverflow.MyDialogEvent.Confirmed<T> createFromParcel(@org.jetbrains.annotations.NotNull()
    android.os.Parcel in) {
        return null;
    }
}

and during compilation I get this error for it (line numbers won't match the sample code, but you can easily identify the matching lines by comparing the method names):

MyDialogEvent.java:167: error: non-static type variable T cannot be referenced from a static context
            public final com.example.stackoverflow.MyDialogEvent.Confirmed<T>[] newArray(int size) {
                                                                                       
MyDialogEvent.java:173: error: non-static type variable T cannot be referenced from a static context
            public final com.example.stackoverflow.MyDialogEvent.Confirmed<T> createFromParcel(@org.jetbrains.annotations.NotNull()

Answer 1

That's a bug in kapt and it's reported here. Actually the java code you posted is a stub class which generated by kapt to run annotation processors on it (as you can see, there is no real implementation, just the structure and annotations). So as a workaround you can move the code with @Parcelize annotations to a separate module where you don't have kapt enabled. kotlin-parcelize itself does not use annotation processors to generate code, it uses a compiler plugin to emit the IR directly I believe.

Update: the issue is fixed in kotlin 1.5

Answer 2

After further checking, I think Parcelable generic type with Parcel constructing fails to compile because T class can not be determined generically based from this reference.

Perhaps an enum could be the last resort.

Answer 3

This is work for me, please check the order of lines carefully

plugins {
    id 'kotlin-android'
    id 'kotlin-parcelize'
    id 'kotlin-kapt'    
   }