Wsrtjtyk

I have one JSON file in my app's data folder.

 {

  "user": [

    {

      "identifier": "1",

      "name": "xyz",

      "contact": [

        {

          "contact": "123"

        },

        {

          "contact": "456"

        }

      ]

    }

  ]

}

Now I want to add a new user at runtime like this.

{

  "user": [

    {

      "identifier": "1",

      "name": "xyz",

      "contact": [

        {

          "contact": "123"

        },

        {

          "contact": "456"

        }

      ]

    }

  ],

  "user": [

    {

      "identifier": "2",

      "name": "abc",

      "contact": [

        {

          "contact": "445"

        },

        {

          "contact": "789"

        }

      ]

    }

  ]

}

For that, I have this code but it simply overrides the existing user.

String lastObject = getStringFronFile(new FileInputStream(file));

        try {

            JSONObject prevJSONObj = new JSONObject(lastObject);

            prevJSONObj.put("sticker_packs",newUserArray);

            writeJsonFile(file,prevJSONObj);

        }

        catch (Exception e) {

            Log.d("Json Error", e.toString());

        }

writeJsonFile is a method for writing in the file.

Any help will be appreciated.

The structure you defined above is wrong, you cannot define two node with the same name user in a JSONObject.

If you want to store a list of user in to a file, you may store it like:

[

    {

        "name":"Jack",

        "age" :20

    },

    {

        "name":"Tom",

        "age" :20

    }

]

By the way, why not use SQLite database?

Gson simplifies this work. Add the gson dependency https://github.com/google/gson or retrofit's gson (both are same)
implementation 'com.squareup.retrofit2:converter-gson:2.4.0'. From your details constructed the following pojo classes :

public class Example {

@SerializedName("user")

@Expose

private List<User> user = null;



public List<User> getUser() {

return user;

}



public void setUser(List<User> user) {

this.user = user;

}

}



public class User {

@SerializedName("identifier")

@Expose

private String identifier;

@SerializedName("name")

@Expose

private String name;

@SerializedName("contact")

@Expose

private List<Contact> contact = null;



public String getIdentifier() {

return identifier;

}



public void setIdentifier(String identifier) {

this.identifier = identifier;

}



public String getName() {

return name;

}



public void setName(String name) {

this.name = name;

}



public List<Contact> getContact() {

return contact;

}



public void setContact(List<Contact> contact) {

this.contact = contact;

}

}



public class Contact {

@SerializedName("contact")

@Expose

private String contact;



public String getContact() {

return contact;

}



public void setContact(String contact) {

this.contact = contact;

}

}

You can use the following snippet to get details from string and append your dynamic data and update the file.

String lastObject = getStringFromFile(new FileInputStream(file));

Example newJsonToReplace = new Example();

List<User> usersList = new ArrayList();

try{

    Type typeOfObject = new TypeToken<Example>() {

    }.getType(); // type you will be getting from string

    Example example = new Gson().fromJson(lastObject, typeOfObject); // converting string to pojo using gson

    if(example != null){

        usersList.addAll(example.getUser());

    }

    usersList.add(yourYourToAdd); // add your user object

    newJsonToReplace.setUser(usersList);

    String updatedList = new Gson().toJson(newJsonToReplace, typeOfObject); // again converting to json to string

    writeJsonFile(updatedList); // will replace the existing content

}catch(Exception exception){

    Log.d("Json Error", e.toString());

}