试图从后端检索对象，但出现致命异常

Question

我想从后端数据库 table 中检索一个对象。调用 "Category" 与此建立关系。这是一个一对多的关系，在 Users table 中称为 "categories"。我真的什么都试过了...我不知道问题出在哪里..请帮帮我！我遇到了这个致命异常：

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

类别class：

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 );
  }
}

类别活动：

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

现在可以使用了！我只需要使用异步方法。

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) {

                        }


                    });




                }

试图从后端检索对象，但出现致命异常

Trying to retrieve object from backendless, but i get fatal exception

database

data-retrieval

relationship

android-studio

backendless