Kotlin convert json string to list of object using Gson

Question

I have a problem with Kotlin to write code for conversion from JSON String to List of objects.

Normally in Java, it is like this:

  Gson gson = new Gson();
    Type type = new TypeToken<List<SomeOjbect>>() {}.getType();
    List<SomeOjbect> measurements = gson.fromJson(json, type);
    return measurements;

However in Kotlin, when i try it like this:

   val gson = Gson()
    val type: Type = TypeToken<List<SomeOjbect>>{}.type
    val measurements : List<SomeOjbect> = gson.fromJson(text, type)
    return measurements

The IDE Android Studio underlines as error the TypeToken saying:

Cannot access ' < init > ': it is public/package/ in 'TypeToken'

and also underlines as error the {} saying:

Type mismatch. Required: Type! Found: () → Unit

So is there a solution to make it work for Kotlin?

Try this, it uses object instead of Type.. measurements : List<SomeOjbect> = gson.fromJson(text, object : TypeToken<List<SomeOjbect>>() {}.type) — Purushotham
– Purushotham, Commented Dec 15, 2017 at 6:19
@Uttam Thanks, it worked. You can post it as an answer and i accept it — K.Os
– K.Os, Commented Dec 15, 2017 at 13:14

Charlie Niekirk · Accepted Answer · 2020-01-14 12:48:31Z

36

You could try doing this instead:

val objectList = gson.fromJson(json, Array<SomeObject>::class.java).asList()

EDIT [14th January 2020]: You should NOT be using GSON anymore. Jake Wharton, one of the projects maintainers, suggests using Moshi, Jackson or kotlinx.serialization.

edited Jan 14, 2020 at 12:48

answered Dec 15, 2017 at 0:46

Charlie Niekirk

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2 Comments

Charlie Niekirk Over a year ago

Link here: reddit.com/r/androiddev/comments/ejjroe/…

Akbolat SSS Over a year ago

Wow! Thats the biggest change in my android networking stack :D

Purushotham · Accepted Answer · 2017-12-18 16:00:55Z

7

Try this, it uses object instead of Type..

measurements : List<SomeOjbect> = gson.fromJson(text, object : TypeToken<List<SomeOjbect>>() {}.type)

answered Dec 18, 2017 at 16:00

Purushotham

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