試圖從後端檢索對象，但我得到致命的異常

Question

我想從後端數據庫表中檢索一個對象。其中稱「類別」與此有關係。 這是一對多關係，在用戶表中稱爲「類別」。 我真的嘗試了一切......我不知道問題出在哪裏..請幫助我！ 我得到這個致命異常：

FATAL EXCEPTION:main 
BackendlessException{ code: 'Internal client exception', message: 'null' } 

分類等級：

package com.backendless.celkituzes_app.data; 

import com.backendless.Backendless; 
import com.backendless.BackendlessCollection; 
import com.backendless.BackendlessUser; 
import com.backendless.async.callback.AsyncCallback; 
import com.backendless.geo.GeoPoint; 
import com.backendless.persistence.BackendlessDataQuery; 

public class Category 
{ 
    private String objectId; 
    private java.util.Date created; 
    private String categoryTitle; 
    private Boolean bonus; 
    private String ownerId; 
    private java.util.Date updated; 
    private java.util.List<BackendlessUser> subscribers; 
    public String getObjectId() 
    { 
    return objectId; 
    } 

    public java.util.Date getCreated() 
    { 
    return created; 
    } 

    public String getCategoryTitle() 
    { 
    return categoryTitle; 
    } 

    public void setCategoryTitle(String categoryTitle) 
    { 
    this.categoryTitle = categoryTitle; 
    } 

    public Boolean getBonus() 
    { 
    return bonus; 
    } 

    public void setBonus(Boolean bonus) 
    { 
    this.bonus = bonus; 
    } 

    public String getOwnerId() 
    { 
    return ownerId; 
    } 

    public java.util.Date getUpdated() 
    { 
    return updated; 
    } 

    public java.util.List<BackendlessUser> getSubscribers() 
    { 
    return subscribers; 
    } 

    public void setSubscribers(java.util.List<BackendlessUser> subscribers) 
    { 
    this.subscribers = subscribers; 
    } 


    public Category save() 
    { 
    return Backendless.Data.of(Category.class).save(this); 
    } 

    public Future<Category> saveAsync() 
    { 
    if(Backendless.isAndroid()) 
    { 
     throw new UnsupportedOperationException("Using this method is restricted in Android"); 
    } 
    else 
    { 
     Future<Category> future = new Future<Category>(); 
     Backendless.Data.of(Category.class).save(this, future); 

     return future; 
    } 
    } 

    public void saveAsync(AsyncCallback<Category> callback) 
    { 
    Backendless.Data.of(Category.class).save(this, callback); 
    } 

    public Long remove() 
    { 
    return Backendless.Data.of(Category.class).remove(this); 
    } 

    public Future<Long> removeAsync() 
    { 
    if(Backendless.isAndroid()) 
    { 
     throw new UnsupportedOperationException("Using this method is restricted in Android"); 
    } 
    else 
    { 
     Future<Long> future = new Future<Long>(); 
     Backendless.Data.of(Category.class).remove(this, future); 

     return future; 
    } 
    } 

    public void removeAsync(AsyncCallback<Long> callback) 
    { 
    Backendless.Data.of(Category.class).remove(this, callback); 
    } 

    public static Category findById(String id) 
    { 
    return Backendless.Data.of(Category.class).findById(id); 
    } 

    public static Future<Category> findByIdAsync(String id) 
    { 
    if(Backendless.isAndroid()) 
    { 
     throw new UnsupportedOperationException("Using this method is restricted in Android"); 
    } 
    else 
    { 
     Future<Category> future = new Future<Category>(); 
     Backendless.Data.of(Category.class).findById(id, future); 

     return future; 
    } 
    } 

    public static void findByIdAsync(String id, AsyncCallback<Category> callback) 
    { 
    Backendless.Data.of(Category.class).findById(id, callback); 
    } 

    public static Category findFirst() 
    { 
    return Backendless.Data.of(Category.class).findFirst(); 
    } 

    public static Future<Category> findFirstAsync() 
    { 
    if(Backendless.isAndroid()) 
    { 
     throw new UnsupportedOperationException("Using this method is restricted in Android"); 
    } 
    else 
    { 
     Future<Category> future = new Future<Category>(); 
     Backendless.Data.of(Category.class).findFirst(future); 

     return future; 
    } 
    } 

    public static void findFirstAsync(AsyncCallback<Category> callback) 
    { 
    Backendless.Data.of(Category.class).findFirst(callback); 
    } 

    public static Category findLast() 
    { 
    return Backendless.Data.of(Category.class).findLast(); 
    } 

    public static Future<Category> findLastAsync() 
    { 
    if(Backendless.isAndroid()) 
    { 
     throw new UnsupportedOperationException("Using this method is restricted in Android"); 
    } 
    else 
    { 
     Future<Category> future = new Future<Category>(); 
     Backendless.Data.of(Category.class).findLast(future); 

     return future; 
    } 
    } 

    public static void findLastAsync(AsyncCallback<Category> callback) 
    { 
    Backendless.Data.of(Category.class).findLast(callback); 
    } 

    public static BackendlessCollection<Category> find(BackendlessDataQuery query) 
    { 
    return Backendless.Data.of(Category.class).find(query); 
    } 

    public static Future<BackendlessCollection<Category>> findAsync(BackendlessDataQuery query) 
    { 
    if(Backendless.isAndroid()) 
    { 
     throw new UnsupportedOperationException("Using this method is restricted in Android"); 
    } 
    else 
    { 
     Future<BackendlessCollection<Category>> future = new Future<BackendlessCollection<Category>>(); 
     Backendless.Data.of(Category.class).find(query, future); 

     return future; 
    } 
    } 

    public static void findAsync(BackendlessDataQuery query, AsyncCallback<BackendlessCollection<Category>> callback) 
    { 
    Backendless.Data.of(Category.class).find(query, callback); 
    } 
} 

CategoryActivity：

package sgtt.celtkituzes_0_1; 

import... 


public class CategoryActivity extends AppCompatActivity { 

    String[] category = {"Általános jó közérzet","Táplálkozás és egészség","Fittség","Család","Kapcsolatok","Szabadidő","Karrier","Személyes fejlődés","Saját kihívások"}; 

    SharedPreferences msgPreferences; 
    SharedPreferences.Editor msgPreferencesEditor; 
    private Boolean fclick; 

    public SharedPreferences loginPreferences; 
    public SharedPreferences.Editor loginPrefsEditor; 

    String password; 

    BackendlessUser backendlessUser= Backendless.UserService.CurrentUser(); 

    @Override 
    protected void onCreate(Bundle savedInstanceState) { 
     super.onCreate(savedInstanceState); 
     setContentView(R.layout.activity_category); 
     Backendless.initApp(this,"19F954A6-2211-7ED0-FF1B-BD05FFD80200", "F445C642-63BF-0D19-FFBB-B06809011C00","v1"); 
//  BackendlessCollection<Category> collection = Backendless.Data.of(Category.class).find(); 




     final ListView CategorylistView = (ListView) findViewById(R.id.CategorylistView); 

     msgPreferences = getSharedPreferences("msgPref", MODE_PRIVATE); 
     msgPreferencesEditor = msgPreferences.edit(); 

     fclick = msgPreferences.getBoolean("msgPref", false); 


     loginPreferences = getSharedPreferences("LoginPrefs", MODE_PRIVATE); 
     loginPrefsEditor = loginPreferences.edit(); 

     ArrayAdapter adapter = new ArrayAdapter(this,android.R.layout.simple_list_item_1,category); 
     CategorylistView.setAdapter(adapter); 


     CategorylistView.setAdapter(new ArrayAdapter<String>(this,android.R.layout.simple_list_item_1,category){ 
      @Override 
      public View getView(int position, View convertView, ViewGroup parent) { 
       TextView textView = (TextView) super.getView(position, convertView, parent); 
       if (position > 1) { 
        textView.setTextColor(0xffcccccc); 
       } 
       if(position <2){ 
        textView.setTextSize(24); 
        textView.setTypeface(null, Typeface.BOLD); 
       } 

       return textView; 
      } 
     }); 


     CategorylistView.setOnItemClickListener(new AdapterView.OnItemClickListener() { 
      @Override 
      public void onItemClick(AdapterView<?> adapterView,View view, int i, long l) { 

       final String category = (String) adapterView.getItemAtPosition(i); 


       BackendlessDataQuery query = new BackendlessDataQuery(); 
       query.setWhereClause("objectId = '8A2BC69E-0894-965F-FF45-B82C60BBEB00'"); 
       //the problem is here i think.. 
       BackendlessCollection<Category> cat1 = Backendless.Persistence.of(Category.class).find(query); 

       if(i==0){ 
        backendlessUser.setProperty("categories",cat1); 
       } 

       if(i==1){ 
       } 
       if(i==2){ 
       } 
       if(i==3){ 
       } 
       if(i==4){ 
       } 
       if(i==5){ 
       } 
       if(i==6){ 
       } 
       if(i==7){ 
       } 
       if(i==8) { 
       } 

      } 
     }); 

    } 

} 

Answer 1

現在，它的工作！我只需要使用異步方法。

if(i==0){ 
        Backendless.Persistence.of(Category.class).findById("8A2BC69E-0894-965F-FF45-B82C60BBEB00", new AsyncCallback<Category>() { 
         @Override 
         public void handleResponse(Category response) { 

          final Category cat1 = response; 

          Toast.makeText(getApplicationContext(),"Done",Toast.LENGTH_SHORT).show(); 

          Backendless.UserService.login(email, password, new AsyncCallback<BackendlessUser>() 
          { 
           @Override 
           public void handleResponse(BackendlessUser backendlessUser) 
           { 
            backendlessUser.setProperty("categories",cat1); 
            Backendless.UserService.update(backendlessUser, new AsyncCallback<BackendlessUser>() { 
             @Override 
             public void handleResponse(BackendlessUser response) { 
              System.out.println("User has been updated"); 
             } 

             @Override 
             public void handleFault(BackendlessFault fault) { 

             } 
            }); 
            Toast.makeText(getApplicationContext(), "Done!", Toast.LENGTH_SHORT).show(); 
           } 

           @Override 
           public void handleFault(BackendlessFault backendlessFault) 
           { 
            System.out.println("Server reported an error - " + backendlessFault.getMessage()); 
           } 
          }); 
         } 

         @Override 
         public void handleFault(BackendlessFault fault) { 

         } 


        }); 




       }