LibGDX: Reading from json file to ArrayList

Question

I need help with reading json file to ArrayList.

I have json file:

[
    {
        "name": "Wall",
        "symbol": "#",      
    },
    {
        "name": "Floor",
        "symbol": ".",
    }
]

I have a class:

public class Tile {

    public String name;
    public String symbol;

}

And I have another class with ArrayList:

public class Data {

    public static ArrayList<Tile> tilesData;

    public static void loadData() {
        tilesData = new ArrayList<Tile>();
        Json json = new Json();
        json.fromJson(Tile.class, Gdx.files.internal("data/tiles.json"));
    }

}

I need to fill this ArrayList with data from json file, but I have some problems. I guess the line

json.fromJson(Tile.class, Gdx.files.internal("data/tiles.json"));

is wrong.

When I try to run it there is

Exception in thread "LWJGL Application" com.badlogic.gdx.utils.SerializationException: Error reading file: data/tiles.json

Caused by: com.badlogic.gdx.utils.SerializationException: Unable to convert value to required type: [
{
    name: Wall,
    symbol: #
},
{
    name: Floor,
    symbol: .
}

I have read the libgdx article about json files, but I found it unclear... I don't understand how to fill array. Please, help me with this case!

Answer 1

Your json file has ArrayList<Tile> stored in it and you are trying to read it as a Tile.

There are two ways to rectify this.

1) You can encapsulate collection of tiles in another class to simplify serialization.

2) Read as ArrayList and convert type later.

ArrayList<JsonValue> list = json.fromJson(ArrayList.class,
                                          Gdx.files.internal("data/tiles.json"));
for (JsonValue v : list) {
    tilesData.add(json.readValue(Tile.class, v));
}

Hope this helps.