How to handle JSON arrays using GSON in Kotlin Android

How to handle JSON arrays using GSON in Kotlin Android.

Here's a step-by-step tutorial on how to handle JSON arrays using GSON in Kotlin for Android:

1. Add GSON dependency to your project:

   • Open your app-level build.gradle file.
   • Inside the dependencies block, add the following line:

     implementation 'com.google.code.gson:gson:2.8.8'
   • Sync your project to download the GSON library.

2. Create a data class to represent the JSON object:

   • Define a Kotlin data class that matches the structure of your JSON object.
   • Each property of the data class should correspond to a key-value pair in the JSON object.
   • For example, if your JSON object has properties like name, age, and email, your data class would look like this:

     data class Person(val name: String, val age: Int, val email: String)

3. Parse JSON array using GSON:

   • Use GSON to convert the JSON array into a list of objects.
   • Create a Gson object:

     val gson = Gson()
   • Use the fromJson method to parse the JSON array into a list of objects:

     val jsonArray = "[{\"name\":\"John\", \"age\":30, \"email\":\"[email protected]\"}, {\"name\":\"Jane\", \"age\":25, \"email\":\"[email protected]\"}]"
     val personList = gson.fromJson(jsonArray, Array<Person>::class.java).toList()

4. Access the data from the parsed JSON array:

   • Iterate over the list of objects to access individual items.
   • For example, to print the name and email of each person in the list:

     for (person in personList) {
         println("Name: ${person.name}")
         println("Email: ${person.email}")
     }

5. Convert a list of objects to JSON array:

   • If you have a list of objects and want to convert it to a JSON array, use GSON.
   • Create a Gson object:

     val gson = Gson()
   • Use the toJson method to convert the list of objects to a JSON array:

     val personList = listOf(Person("John", 30, "[email protected]"), Person("Jane", 25, "[email protected]"))
     val jsonArray = gson.toJson(personList)

6. Handle nested JSON arrays:

   • If your JSON array contains nested arrays, you can use GSON to parse them as well.
   • Define nested data classes to represent the structure of the nested arrays.
   • For example, if your JSON structure is like this:

     [
       {
         "name": "John",
         "friends": [
           {
             "name": "Jane",
             "age": 25,
             "email": "[email protected]"
           },
           {
             "name": "Tom",
             "age": 27,
             "email": "[email protected]"
           }
         ]
       },
       {
         "name": "Mary",
         "friends": [
           {
             "name": "Alex",
             "age": 29,
             "email": "[email protected]"
           }
         ]
       }
     ]
   • Create nested data classes to represent the structure:

     data class Friend(val name: String, val age: Int, val email: String)
     data class PersonWithFriends(val name: String, val friends: List<Friend>)

That's it! You now know how to handle JSON arrays using GSON in Kotlin for Android. You can use these steps to parse and manipulate JSON arrays in your own projects.