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Android and GSON throwing No-Args Constructor not found exception

I am having a problem with GSON in my Android app.

JSON Input

[
    {"id":"1202","parent_id":"0","agrpcount":"0","disp_order":"1","code":"PROD-NEW","name":"New Products","active":"1"},
    {"id":"1119","parent_id":"0","agrpcount":"0","disp_order":"2","code":"PROD-VID","name":"\\\"How To\\\" Videos","active":"1"},
    {"id":"1685","parent_id":"0","agrpcount":"0","disp_order":"3","code":"SUPP-RESOUR","name":"Support Resources","active":"1"},
    {"id":"49","parent_id":"0","agrpcount":"0","disp_order":"109","code":"EQ","name":"Equipment for Sign Making","active":"1"},
    {"id":"22","parent_id":"0","agrpcount":"0","disp_order":"110","code":"application-tape","name":"Application Tapes","active":"1"}
]

Container class for each array item

public class Category {
    public int id;
    public int parent_id;
    public int agrpcount;
    public int disp_order;
    public String code;
    public String name;
    public int active;
}

Class to load category array

public static List<Category> getCategories(){
    Category[] cats;

    Gson gson = new Gson();

    cats = gson.fromJson(strJSON, Category[].class);

    List<Category> CatsList = Arrays.asList(cats);
    return CatsList;
}

When I run this code I get the following in the Log

02-28 15:15:42.471: ERROR/AndroidRuntime(777): Caused by: java.lang.RuntimeException: No-args constructor for class com.signwarehouse.catalog.SWService$Category does not exist. Register an InstanceCreator with Gson for this type to fix this problem.
02-28 15:15:42.471: ERROR/AndroidRuntime(777):     at com.google.gson.MappedObjectConstructor.constructWithNoArgConstructor(MappedObjectConstructor.java:64)
02-28 15:15:42.471: ERROR/AndroidRuntime(777):     at com.google.gson.MappedObjectConstructor.construct(MappedObjectConstructor.java:53)
02-28 15:15:42.471: ERROR/AndroidRuntime(777):     at com.google.gson.JsonObjectDeserializationVisitor.constructTarget(JsonObjectDeserializationVisitor.java:40)
02-28 15:15:42.471: ERROR/AndroidRuntime(777):     at com.google.gson.JsonDeserializationVisitor.getTarget(JsonDeserializationVisitor.java:56)
02-28 15:15:42.471: ERROR/AndroidRuntime(777):     at com.google.gson.ObjectNavigator.accept(ObjectNavigator.java:109)
02-28 15:15:42.471: ERROR/AndroidRuntime(777):     at com.google.gson.JsonDeserializationVisitor.visitChild(JsonDeserializationVisitor.java:107)
02-28 15:15:42.471: ERROR/AndroidRuntime(777):     at com.google.gson.JsonDeserializationVisitor.visitChildAsObject(JsonDeserializationVisitor.java:95)
02-28 15:15:42.471: ERROR/AndroidRuntime(777):     at com.google.gson.JsonArrayDeserializationVisitor.visitArray(JsonArrayDeserializationVisitor.java:72)
02-28 15:15:42.471: ERROR/AndroidRuntime(777):     at com.google.gson.ObjectNavigator.accept(ObjectNavigator.java:117)
02-28 15:15:42.471: ERROR/AndroidRuntime(777):     at com.goo开发者_如何转开发gle.gson.JsonDeserializationContextDefault.fromJsonArray(JsonDeserializationContextDefault.java:64)
02-28 15:15:42.471: ERROR/AndroidRuntime(777):     at com.google.gson.JsonDeserializationContextDefault.deserialize(JsonDeserializationContextDefault.java:49)
02-28 15:15:42.471: ERROR/AndroidRuntime(777):     at com.google.gson.Gson.fromJson(Gson.java:568)
02-28 15:15:42.471: ERROR/AndroidRuntime(777):     at com.google.gson.Gson.fromJson(Gson.java:515)
02-28 15:15:42.471: ERROR/AndroidRuntime(777):     at com.google.gson.Gson.fromJson(Gson.java:484)
02-28 15:15:42.471: ERROR/AndroidRuntime(777):     at com.google.gson.Gson.fromJson(Gson.java:434)
02-28 15:15:42.471: ERROR/AndroidRuntime(777):     at com.google.gson.Gson.fromJson(Gson.java:406)

I tried adding a no-args constructor to the Category class, but this didn't help. No surprise since Java creates it automatically.

Does anyone have any idea how to fix this?

Thanks.


Trying making the Category class a public static class...

public static class Category {/* fields */}

I bet what's happening is since you didn't make the class static it is trying to create your parent/outer class (com.signwarehouse.catalog.SWService) first which probably doesn't have a no-arg constructor.

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