凌空响应Android后如何返回值

Question

我是Android新手。我试图通过截击请求从数据库中收集数据。但是，该计划在价值进入之前继续进行。任何人都有解决方案来解决这个问题吗？我用断点来检查程序的顺序。在调用onSuccess函数之前，它将在DatabaseCategory中运行return categoryList。

这是调用DatabaseCategory

的类

public class DatabaseFacade implements Database {

private DatabaseCategory databaseCategory;

public DatabaseFacade(Context context) {
    databaseCategory = new DatabaseCategory(context);
}

@Override
public List<Category> readCategory() {
    return (List<Category>) databaseCategory.loadData(DatabaseUrl.getCategoryReadUrl(), null);
}

}

这是加载数据的类

public class DatabaseCategory extends DatabaseAbstract{

private Context context;
private List<?> categoryList;

public DatabaseCategory(Context context) {
    this.context = context;
}

@Override
public List<?> loadData(String url, Object object) {
    databaseLoad = new DatabaseLoad(context, ObjectType.CATEGORY, url);
    databaseLoad.execute(new CallBack() {
        @Override
        public void onSuccess(List<?> list) {
            categoryList = list;
        }

        @Override
        public void onFail(String msg) {
            // Do Stuff
        }
    });
    return categoryList;
}

这是处理截击请求的类

public class DatabaseLoad {

private static final String FAIL_MESSAGE = "Some error occur. Please try later.";
private static final String STATUS_CODE = "success";
private static final int SUCCESS = 1;
private Context context;
private ObjectType objectType;
private String url;
private JSONObject json;
private List<?> loadList;

public DatabaseLoad(Context context, ObjectType type, String url) {
    this.context = context;
    this.objectType = type;
    this.url = url;
}

public void execute(final CallBack onCallBack) {

    StringRequest stringRequest = new StringRequest(Request.Method.POST, url,
            new Response.Listener<String>() {
                @Override
                public void onResponse(String s) {

                    JSONObject obj;
                    try {
                        obj = new JSONObject(s);
                        if(obj.getInt(STATUS_CODE)==SUCCESS){
                            Log.d("logindatabase","success");
                            switch (objectType) {
                                case CATEGORY:
                                    loadList = loadCategory(obj);
                                    break;

                                default:
                                    break;
                            }
                            onCallBack.onSuccess(loadList);
                        }else{
                            Log.d("logindatabase","fail");
                            Toast.makeText(context, FAIL_MESSAGE , Toast.LENGTH_LONG).show();
                        }
                    } catch (JSONException e) {
                        e.printStackTrace();
                        Toast.makeText(context, FAIL_MESSAGE , Toast.LENGTH_LONG).show();
                        onCallBack.onFail(e.toString());
                    }
                }
            },
            new Response.ErrorListener() {
                @Override
                public void onErrorResponse(VolleyError volleyError) {

                    //Showing toast
                    Toast.makeText(context, volleyError.getMessage().toString(), Toast.LENGTH_LONG).show();
                }
            }){
        @Override
        protected Map<String, String> getParams() throws AuthFailureError {
            //Creating parameters
            Map<String,String> params;
            //Adding parameters
            switch (objectType) {
                case CATEGORY:
                    params = loadCategoryParameter();
                    break;

                default:
                    params = new Hashtable<String, String>();
                    break;
            }

            //returning parameters
            return params;
        }
    };

    //Creating a Request Queue
    RequestQueue requestQueue = Volley.newRequestQueue(context.getApplicationContext());

    //Adding request to the queue
    requestQueue.add(stringRequest);



}

private Map<String,String> loadCategoryParameter() {
    Map<String,String> params = new Hashtable<String, String>();
    return params;
}

private List<Category> loadCategory(JSONObject obj) throws JSONException {
    List<Category> categoryList = new ArrayList<>();
    JSONArray categoryArray ;
    categoryArray = obj.getJSONArray("posts");

    for (int i = 0; i < categoryArray.length(); i++) {
        JSONObject c = categoryArray.getJSONObject(i);
        int id = c.getInt("id");
        String name = c.getString("name");
        String type = c.getString("type");
        String image = c.getString("image");
        Category category = new Category(id,name,type,"",image);
        categoryList.add(category);
    }
    //Log.d("categorylist",obj.toString());
    return categoryList;
}
}