makeJSONObject is returning JSONObject

Your code should be

saveCompo.setOnClickListener(new View.OnClickListener() {
        @Override
        public void onClick(View v) {
            setName();
            createJSONFolder();
            CompositionJso obj = new CompositionJso();
            JSONObject  jsonObject = obj.makeJSONObject(compoTitle, compoDesc, imgPaths, imageViewPaths);
            MyCompositionsListActivity.buildList();

            try {
                Writer output = null;
                File file = new File("storage/sdcard/MyIdea/MyCompositions/" + compoTitle + ".json");
                output = new BufferedWriter(new FileWriter(file));
                output.write(jsonObject.toString());
                output.close();
                Toast.makeText(getApplicationContext(), "Composition saved", Toast.LENGTH_LONG).show();

            } catch (Exception e) {
                Toast.makeText(getBaseContext(), e.getMessage(), Toast.LENGTH_LONG).show();
            }
            finish();
        }
    });

Place your json file under assets folder and read this as a String.

First, we need to create an extension to read the file. This extension takes file name as input.

fun AssetManager.readFile(fileName: String) = open(fileName)
    .bufferedReader()
    .use { it.readText() }

Now, use the extension to read the file as a String.

val jsonString = context.assets.readFile("file_name.json")

For more details you can look at this: https://github.com/ArtemBotnev/TelegramCharts/blob/master/app/src/main/java/ru/artembotnev/telegramcompetition/Repository.kt

Anything that you package into the APK will be read-only, as the APK is a binary file, and is not expanded on installation. So just moving your assets to a new package will not help. And the 'src' directory does not appear in the APK.

You'll have to copy your assets to Android's file system at runtime, and make any modifications to that copy.

Android now has a lot of restrictions about where and how you can read and write files, so you'll probably want to read this very carefully: https://developer.android.com/training/data-storage

In 2019 no-one is really parsing JSON manually. It's much easier to use Gson library. It takes as an input your object and spits out JSON string and vice-versa.

Example:

data class MyClass(@SerializedName("s1") val s1: Int)

val myClass: MyClass = Gson().fromJson(data, MyClass::class.java)
val outputJson: String = Gson().toJson(myClass)

This way you're not working with JSON string directly but rather with Kotlin object which is type-safe and more convenient. Look at the docs. It's pretty big and easy to understand

Here is some tutorials:

• https://www.youtube.com/watch?v=f-kcvxYZrB4
• http://www.studytrails.com/java/json/java-google-json-introduction/
• https://www.tutorialspoint.com/gson/index.htm

UPDATE: If you really want to use JSONObject then use its constructor with a string parameter which parses your JSON string automatically.

val jsonObject = JSONObject(data)