Unable to Loop through dynamic json string recursively in android

问题

This is my JSON String (this changes dynamically):

This is one json object from the entire json string which is an array. If the JSON object has value greater than 1 for "ChildExists" (for example 4 like below), an array called "Categories" appears and 4 objects will be shown. If the childExist value of any of those objects become greater than 1, a json array called "Categories" will appear.

This will happen over and over again if the object's value for "childExists" is greater than 0. I created 2 model classes for this with the following attributes :

public class Menu implements Serializable{

    private static final long serialVersionUID = -3407147461924698222L;

    String parentName;
    String position;
    String childExists;
    String categoryName;
    String categoryID;
    String parentID;
    List<Category> categories = new ArrayList<Category>();

       //getters and setters

}

public class Category implements Serializable{

    private static final long serialVersionUID = -3407147461924698222L;

    String parentName;
    String position;
    String childExists;
    String categoryName;
    String categoryID;
    String parentID;

        //getters and setters

}

This is how I tried to break down the json:

public static ArrayList<Menu> getMenuTreeBreakDown(JSONArray arg0) throws JSONException {

        ArrayList<Menu> menuList = new ArrayList<Menu>();
        for(int i = 0; i < arg0.length(); i++){
            JSONObject jsonCategoryObject = arg0.getJSONObject(i);
            Menu menu = new Menu();

            String parentName = jsonCategoryObject.getString("ParentName");
            String position = jsonCategoryObject.getString("Position");
            String childExists = jsonCategoryObject.getString("ChildExists");
            String categoryName = jsonCategoryObject.getString("Category_Name");
            String categoryID = jsonCategoryObject.getString("Category_ID");
            String parentID = jsonCategoryObject.getString("Parent_ID");

            menu.setParentName(parentName);
            menu.setPosition(position);
            menu.setChildExists(childExists);
            menu.setCategoryName(categoryName);
            menu.setCategoryID(categoryID);
            menu.setParentID(parentID);

            if(!childExists.equalsIgnoreCase("0")){
                //this part should happen over and over again if there is a category[]
                JSONArray categoryArray = new JSONArray(jsonCategoryObject.getString("Categories"));

                for (int x = 0; x < categoryArray.length(); x++){

                    JSONObject jsonProductObject1 = categoryArray.getJSONObject(x);
                    Category category = new Category();

                    category.setParentName(jsonProductObject1.getString("ParentName"));
                    category.setPosition(jsonProductObject1.getString("Position"));
                    category.setChildExists(jsonProductObject1.getString("ChildExists"));
                    category.setCategoryName(jsonProductObject1.getString("Category_Name"));
                    category.setCategoryID(jsonProductObject1.getString("Category_ID"));
                    category.setParentID(jsonProductObject1.getString("Parent_ID"));

                    menu.getCategories().add(category);

                }
            }
            menuList.add(menu);
        }
        return menuList;
    }

So far I could not get the correct results. Any help is greatly appreciated!

//got this working:

Used GSON, changed the model class:

public class Menu{

    @SerializedName("ParentName")
    String parentName;
    @SerializedName("Position")
    String position;
    @SerializedName("ChildExists")
    String childExists;
    @SerializedName("Category_Name")
    String categoryName;
    @SerializedName("Category_ID")
    String categoryID;
    @SerializedName("Parent_ID")
    String parentID;
    @SerializedName("Categories")
    List<Menu> categories = new ArrayList<Menu>();
//getters and setters
}

ArrayList<Menu> menuList = new ArrayList<Menu>();
    Gson gson = new Gson();
    JsonParser parser = new JsonParser();
    JsonArray jArray = parser.parse(arg0.toString()).getAsJsonArray();

    for(JsonElement obj : jArray )
    {
        Menu menu = gson.fromJson( obj , Menu.class);
        menuList.add(menu);
    }

回答1:

Did you debug and check where exactly does it break?

Use a for each loop where you can instead of for(;;)

http://docs.oracle.com/javase/1.5.0/docs/guide/language/foreach.html

How does the Java 'for each' loop work?

Also, If you have a complicated json, you may be better off using Gson to map data and your model classes. Eg.:

    Gson gson = new Gson();
    ModelClass modelClass= new ModelClass();
    modelClass= gson.fromJson(responseContent,ModelClass.class); 
//where responseContent is your jsonString
    Log.i("Web service response", ""+modelClass.toString());

https://code.google.com/p/google-gson/

For Naming discrepancies(according to the variables in webservice), can use annotations like @SerializedName. (So no need to use Serializable)

来源：https://stackoverflow.com/questions/21480634/unable-to-loop-through-dynamic-json-string-recursively-in-android