转换ArrayList <Object> 使用Gson进入Json

Question

To start off, i'm reasonable new to programming in general. For school i'm working on an android project in which i would like to be able to save data using SharedPreferences, using Gson to turn an ArrayList into Json. However, whenever I try to run it (emulator) I get the following messages in logcat:

Do full code cache collection, code=125KB, data=66KB
After code cache collection, code=104KB, data=41KB
Background concurrent copying GC freed 36221(1156KB) AllocSpace objects, 3(60KB) LOS objects, 49% free, 1708KB/3MB, paused 5.863ms total 115.252ms
Do partial code cache collection, code=123KB, data=56KB
After code cache collection, code=123KB, data=56KB
Increasing code cache capacity to 512KB

This will go on for a while untill my app crashes. I do not run into this problem when saving other data the same way I'm trying to do here.

Code:

adding objects to array

for(int x = 0; x < board.getWidth(); x++ ) {
                for( int y = 0; y < board.getHeight(); y++ ) {

                    Field field = (Field) MainActivity.game.getGameBoard().getObject(x, y);
                    fieldArray.add(field);
                }
            }

converting and saving

SharedPreferences prefs = PreferenceManager.getDefaultSharedPreferences(getApplicationContext());
SharedPreferences.Editor editor = prefs.edit();
Gson objectGson = new Gson();
String objectJson = objectGson.toJson(fieldArray);
edits.putString("gameobjects", objectJson);
editor.apply();

What could be the problem here?

Answer 1

Try this

Type listType = new TypeToken<ArrayList<YourObject>>(){}.getType();

listGalerias = new Gson().fromJson(json, listType);

Answer 2

Ok, I tried here something like this, I have an object Post with some fields, I used Gson to populate this object

val url = "http://www.projectconnect.com.br/make/api/post/list/list.php"

val json = URL(url).readText()

val gson = Gson()

val retorno = gson.fromJson(json, Retorno::class.java)

val posts : List<Post> = retorno.list

the result was this Post object

later I made this

val arrayPosts = arrayOfNulls<Post>(posts.size)
arrayPosts.set(0, posts[0])

for (i in 0 until posts.size) {
    arrayPosts[i] = posts[i]
}

val objectJson = gson.toJson(arrayPosts)

and the result was this my objectJson populated

here is the objectJson value