Back4App，如何更新关系数据数组

Posted 2023-04-19

【中文标题】Back4App，如何更新关系数据数组

【英文标题】：Back4App, how to update a relational data array

【发布时间】：2021-08-11 04:49:56

【问题描述】：

每当我尝试将评论类数据保存到我的 Post 类时，终端都会输出此消息，我不确定如何正确更新 back4app 中的关系数据这是错误消息。 com.parse.ParseException: java.lang.IllegalStateException: 无法编码与未保存 ParseObject 的关联

package com.example.rentahome.fragments;

import android.os.Bundle;

import androidx.annotation.NonNull;
import androidx.annotation.Nullable;
import androidx.fragment.app.Fragment;
import androidx.recyclerview.widget.LinearLayoutManager;

import android.provider.ContactsContract;
import android.util.Log;
import android.view.LayoutInflater;
import android.view.View;
import android.view.ViewGroup;
import android.widget.Button;
import android.widget.EditText;
import android.widget.RatingBar;
import android.widget.Toast;

import com.example.rentahome.Post;
import com.example.rentahome.R;
import com.example.rentahome.ReviewAdapter;
import com.example.rentahome.Reviews;
import com.parse.FindCallback;
import com.parse.ParseException;
import com.parse.ParseObject;
import com.parse.ParseQuery;
import com.parse.ParseRelation;
import com.parse.ParseUser;
import com.parse.SaveCallback;

import java.util.ArrayList;
import java.util.List;

/**
 * A simple @link Fragment subclass.
 * Use the @link ReviewFragment#newInstance factory method to
 * create an instance of this fragment.
 */
public class ReviewFragment extends Fragment 

    // TODO: Rename parameter arguments, choose names that match
    // the fragment initialization parameters, e.g. ARG_ITEM_NUMBER
    private static final String ARG_PARAM1 = "param1";
    private static final String ARG_PARAM2 = "param2";

    public Post loadpost;
    public EditText description;
    public RatingBar ratingBar;
    public Button submit;

    public void updatePost(Post post)
        loadpost = post;
    

    // TODO: Rename and change types of parameters
    private String mParam1;
    private String mParam2;

    public ReviewFragment() 
        // Required empty public constructor
    

    /**
     * Use this factory method to create a new instance of
     * this fragment using the provided parameters.
     *
     * @param param1 Parameter 1.
     * @param param2 Parameter 2.
     * @return A new instance of fragment ReviewFragment.
     */
    // TODO: Rename and change types and number of parameters
    public static ReviewFragment newInstance(String param1, String param2) 
        ReviewFragment fragment = new ReviewFragment();
        Bundle args = new Bundle();
        args.putString(ARG_PARAM1, param1);
        args.putString(ARG_PARAM2, param2);
        fragment.setArguments(args);
        return fragment;
    

    @Override
    public void onCreate(Bundle savedInstanceState) 
        super.onCreate(savedInstanceState);
        if (getArguments() != null) 
            mParam1 = getArguments().getString(ARG_PARAM1);
            mParam2 = getArguments().getString(ARG_PARAM2);
        
    

    @Override
    public View onCreateView(LayoutInflater inflater, ViewGroup container,
                             Bundle savedInstanceState) 
        // Inflate the layout for this fragment
        return inflater.inflate(R.layout.fragment_review, container, false);
    

    @Override
    public void onViewCreated(@NonNull View view, @Nullable Bundle savedInstanceState)
        super.onViewCreated(view, savedInstanceState);




        description = view.findViewById(R.id.submitReview_description);
        ratingBar = view.findViewById(R.id.submitReview_ratingbar);
        submit = view.findViewById(R.id.submitReview_submitbtn);

        submit.setOnClickListener(new View.OnClickListener() 
            @Override
            public void onClick(View v) 

                ParseRelation<ParseObject> relation = loadpost.getRelation("Reviews");

                if(ratingBar.getNumStars() == 0)
                    Toast.makeText(getContext(), "Rate the house!",Toast.LENGTH_SHORT).show();
                else if(description.getText().toString().isEmpty())
                    Toast.makeText(getContext(),"Describe the house!", Toast.LENGTH_SHORT).show();
                else
                    ParseObject temp = ParseObject.create("Reviews");
                    temp.put("Description",description.getText().toString());
                    temp.put("author", ParseUser.getCurrentUser());
                    temp.put("likesCount",0);
                    temp.put("dislikesCount",0);
                    temp.put("rating", (float)ratingBar.getNumStars());


                    temp.saveInBackground(new SaveCallback() 
                        @Override
                        public void done(ParseException e) 

                        
                    );


                    relation.add(temp);


                    loadpost.saveInBackground(new SaveCallback() 
                        @Override
                        public void done(ParseException e) 
                            if(e!=null)
                                Log.e("ReviewFragment","Issue with saving posts..", e);
                                Toast.makeText(getContext(), "Error while saving", Toast.LENGTH_SHORT).show();
                                return;
                            

                        
                    );

                    Homefragment nextFrag= new Homefragment();

                    getActivity().getSupportFragmentManager().beginTransaction()
                            .replace(R.id.flContainer, nextFrag)
                            .addToBackStack(null)
                            .commit();
                

            
        );

    

基本思想是从现有帖子数据中获取加载帖子并创建评论对象，然后将其附加到加载帖子并保存。 我使用此文档试图找出我的解决方案 https://docs.parseplatform.org/android/guide/#relational-data

【参考方案1】：

Reviews temp2 = new Reviews();
                    temp2.setAuthor(ParseUser.getCurrentUser());
                    temp2.setDescription(description.getText().toString());
                    temp2.setRating((float)ratingBar.getNumStars());
                    temp2.setdislikesCount(0);
                    temp2.setlikesCount(0);
                    temp2.saveInBackground(new SaveCallback() 
                        @Override
                        public void done(ParseException e) 
                            if(e!=null)
                                Log.e("ReviewFragment","Issue with saving posts..", e);
                                Toast.makeText(getContext(), "Error while saving", Toast.LENGTH_SHORT).show();
                                return;
                            

                            relation.add(temp2);
                            loadpost.saveInBackground(new SaveCallback() 
                                @Override
                                public void done(ParseException e) 
                                    if(e!=null)
                                        Log.e("ReviewFragment","Issue with saving posts..", e);
                                        Toast.makeText(getContext(), "Error while saving", Toast.LENGTH_SHORT).show();
                                        return;
                                    

                                
                            );

                        
                    );

我所要做的就是调用一个对象并将其保存在后台保存函数中。