How to get data from [Object] android

Question

I am getting this response from my Express API Call.

Here's the Response:

{
    "responseData": [{
        "unitNames": [
            "Matrices",
            "Complex Numbers"
        ],
        "subject": "maths",
        "unitTopics": {
            "1": [{
                    "topicName": "1.1 Introduction",
                    "topicURL": ""
                },
                {
                    "topicName": "1.2 Square Matrix",
                    "topicURL": ""
                }

            ],
            "2": [{
                    "topicName": "2.1 Numbers",
                    "topicURL": ""
                }

            ]
        }
    }]
}

I got the response by using Retrofit in Android. It works great.But it can't parse Objects

Here's my Problem in Android Side.

{
        "responseData": [{
            "unitNames": [
                "Matrices",
                "Complex Numbers"
            ],
            "subject": "maths",
            "unitTopics": {
                "1": [[Object],
                    [Object]
    
                ],
                "2": [[Object]
    
                ]
            }
        }]
    }

Its showing Object instead of my Data. How to fix this

Here's the Code:

System.out.println(response.body().getResponseData())
String received_data = response.body().getResponseData();
received_data_sub_units_topics_json = new JSONArray("["+received_data+"]");
System.out.println("MAIN2 "+received_data_sub_units_topics_json);

After converting to jsonarray, it shows like this,

{
        "responseData": [{
            "unitNames": [
                "Matrices",
                "Complex Numbers"
            ],
            "subject": "maths",
            "unitTopics": {
                "1": [["Object"],
                    ["Object"]
    
                ],
                "2": [["Object"]
    
                ]
            }
        }]
    }

Please help me with some solutions

Answer 1

For json i always use the library com.fasterxml.jackson.

You can use too org.json.JSONArray, org.json.JSONObject.

Here is an example of each one: 1- jackson

For implements this (is a bit long but you will convert it to java classes, so, you will can edit the values and obtain it more easily than if you use JSONObject), you have to create classes wich has the same structure than your json:

public class principalClass {
     ArrayList<ResponseData> responseData;  
     ...
     //Getters, setters and constructors
}

public class ResponseData {
    public ArrayList<String> unitNames;
    public String subject;
    public UnitTopics unitTopics;
    ...
    //Getters, setters and constructors
}

public class UnitTopics {
    public ArrayList<Topics> first;
    public ArrayList<Topics> second;
    ...
    //Getters, setters and constructors
}

public class Topics {
    public String topicName;
    public String topicURL;
    ...
    //Getters, setters and constructors
}

Something like that, and then you use jackson to pass your json to you class principalClass:

ObjectMapper obj= new ObjectMapper();
PrincipalClass principal= obj.readValue(json, PrincipalClass.class);

The second posibility is to convert the values to JSONArray and JSONObject:

JSONObject bodyJSON = new JSONObject(json);

JSONArray responseData = bodyJSON.getJSONArray("responseData");

JSONArray unitNames= responseData.getJSONArray(0);
JSONObject subject= responseData.getJSONObject(1);
...

And if u want, u can loop through a JSONArray:

for (int i = 0; i < unitNames.length(); i++) {     
     String element = unitNames.getString(i);     
}

Answer 2

Hey have you tried converting this JSON Object to a POJO. I'd recommend using: This website

It saves a lot of time and effort. These will be your model classes:

package com.example.app;

import java.io.Serializable;
import java.util.List;
import javax.annotation.Generated;
import com.google.gson.annotations.Expose;
import com.google.gson.annotations.SerializedName;


public class ResponseDatum implements Serializable
{

@SerializedName("unitNames")
@Expose
private List<String> unitNames = null;
@SerializedName("subject")
@Expose
private String subject;
@SerializedName("unitTopics")
@Expose
private UnitTopics unitTopics;


public ResponseDatum() {
}


public ResponseDatum(List<String> unitNames, String subject, UnitTopics unitTopics) {
super();
this.unitNames = unitNames;
this.subject = subject;
this.unitTopics = unitTopics;
}

public List<String> getUnitNames() {
return unitNames;
}

public void setUnitNames(List<String> unitNames) {
this.unitNames = unitNames;
}

public String getSubject() {
return subject;
}

public void setSubject(String subject) {
this.subject = subject;
}

public UnitTopics getUnitTopics() {
return unitTopics;
}

public void setUnitTopics(UnitTopics unitTopics) {
this.unitTopics = unitTopics;
}

}

package com.example.app;

import java.io.Serializable;
import java.util.List;
import javax.annotation.Generated;
import com.google.gson.annotations.Expose;
import com.google.gson.annotations.SerializedName;

public class ResponseObject implements Serializable
{

@SerializedName("responseData")
@Expose
private List<ResponseDatum> responseData = null;


public ResponseObject() {
}


public ResponseObject(List<ResponseDatum> responseData) {
super();
this.responseData = responseData;
}

public List<ResponseDatum> getResponseData() {
return responseData;
}

public void setResponseData(List<ResponseDatum> responseData) {
this.responseData = responseData;
}

}


package com.example.app;

import java.io.Serializable;
import java.util.List;
import javax.annotation.Generated;
import com.google.gson.annotations.Expose;
import com.google.gson.annotations.SerializedName;

public class UnitTopics implements Serializable
{

@SerializedName("1")
@Expose
private List<com.example.app._1> _1 = null;
@SerializedName("2")
@Expose
private List<com.example.app._2> _2 = null;



public UnitTopics() {
}


public UnitTopics(List<com.example.app._1> _1, List<com.example.app._2> _2) {
super();
this._1 = _1;
this._2 = _2;
}

public List<com.example.app._1> get1() {
return _1;
}

public void set1(List<com.example.app._1> _1) {
this._1 = _1;
}

public List<com.example.app._2> get2() {
return _2;
}

public void set2(List<com.example.app._2> _2) {
this._2 = _2;
}

}


package com.example.app;

import java.io.Serializable;
import javax.annotation.Generated;
import com.google.gson.annotations.Expose;
import com.google.gson.annotations.SerializedName;

public class _1 implements Serializable
{

@SerializedName("topicName")
@Expose
private String topicName;
@SerializedName("topicURL")
@Expose
private String topicURL;




public _1() {
}


public _1(String topicName, String topicURL) {
super();
this.topicName = topicName;
this.topicURL = topicURL;
}

public String getTopicName() {
return topicName;
}

public void setTopicName(String topicName) {
this.topicName = topicName;
}

public String getTopicURL() {
return topicURL;
}

public void setTopicURL(String topicURL) {
this.topicURL = topicURL;
}

}


package com.example.app;

import java.io.Serializable;
import javax.annotation.Generated;
import com.google.gson.annotations.Expose;
import com.google.gson.annotations.SerializedName;


public class _2 implements Serializable
{

@SerializedName("topicName")
@Expose
private String topicName;
@SerializedName("topicURL")
@Expose
private String topicURL;



public _2() {
}


public _2(String topicName, String topicURL) {
super();
this.topicName = topicName;
this.topicURL = topicURL;
}

public String getTopicName() {
return topicName;
}

public void setTopicName(String topicName) {
this.topicName = topicName;
}

public String getTopicURL() {
return topicURL;
}

public void setTopicURL(String topicURL) {
this.topicURL = topicURL;
}

}

Answer 3

You can use gson converter with retrofit to convert your json data to java object model class

implementation 'com.squareup.retrofit2:converter-gson:2.4.0'

Or you can convert json data to model class like

Gson gson = new Gson();
String jsonInString = "{your json data}";
ResponseModel response= gson.fromJson(jsonInString, ResponseModel.class);