Saving ArrayLists in SQLite databases

In my case it was ArrayList of POJO classes Note

private String mNoteTitle;
private int mFingerIndex;
private Point mNoteCoordinates;

public Note(String noteTitle, int fingerIndex, Point noteCoordinates) {
    this.mNoteTitle = noteTitle;
    this.mFingerIndex = fingerIndex;
    this.mNoteCoordinates = noteCoordinates;
}

As manual says JSONObject supports only following types: Object: a JSONObject, JSONArray, String, Boolean, Integer, Long, Double, NULL, or null. May not be NaNs or infinities. So, I should break my Note class into supported objects.

 JSONObject json = new JSONObject();
    JSONArray jsonArray = new JSONArray();

    for(Note note: chordShape.getNotes()){
        JSONObject singleNoteJsonObject = new JSONObject();

        try {
            singleNoteJsonObject.put(SHAPE_NOTE_TITLE, note.getNoteTitle());
            singleNoteJsonObject.put(SHAPE_NOTE_FINGER_INDEX, note.getFingerIndex());
            singleNoteJsonObject.put(SHAPE_NOTE_X, note.getNoteCoordinates().x);
            singleNoteJsonObject.put(SHAPE_NOTE_Y, note.getNoteCoordinates().y);
        } catch (JSONException e){
            e.printStackTrace();
        }

        jsonArray.put(singleNoteJsonObject);

    }

Pack created array into JSONObject.

try {
        json.put(SHAPE_NOTES, jsonArray);
        Log.i(TAG, json.toString());
    } catch (JSONException e){
        e.printStackTrace();
    }

Create String.

String notesList = json.toString();

Put created String in ContentValues, cause in my case it's Android app

if(notesList.length() > 0){
        contentValues.put(DatabaseHelper.SHAPE_NOTES_LIST, notesList);
    }

And when i should read values from SQLite database.

ArrayList<Note> notes = new ArrayList<>();
    while(cursor.moveToNext()){
        JSONObject jsonNotes = null;
        try {
           jsonNotes = new JSONObject(cursor.getString(cursor.getColumnIndex(DatabaseHelper.SHAPE_NOTES_LIST)));
        } catch (JSONException e){
            e.printStackTrace();
        }

        if(jsonNotes != null){
            Log.i(TAG, jsonNotes.toString());
            JSONArray jsonArray = jsonNotes.optJSONArray(SHAPE_NOTES);
            for(int i = 0; i < jsonArray.length(); i++){
                Note note = null;
                JSONObject arrayObject = null;

                try {
                    arrayObject = jsonArray.getJSONObject(i);
                } catch (JSONException e){
                    e.printStackTrace();
                }

                if(arrayObject != null){
                    try {
                        note = new Note(
                            arrayObject.getString(SHAPE_NOTE_TITLE),
                                arrayObject.getInt(SHAPE_NOTE_FINGER_INDEX),
                                new Point(
                                        arrayObject.getInt(SHAPE_NOTE_X),
                                        arrayObject.getInt(SHAPE_NOTE_Y)
                                )
                        );
                    } catch (JSONException e){
                        e.printStackTrace();
                    }
                }


                if(note != null){
                    notes.add(note);
                }
            }
        }
    }
    cursor.close();

You cannot insert ArrayList directly into Sqlite. Instead, you could use JSONObject (org.json.JSONObject) to insert the ArrayList. Please check below snippet, you can try something like below....

To insert,

JSONObject json = new JSONObject();
json.put("uniqueArrays", new JSONArray(items));
String arrayList = json.toString();

Insert the string into db.

To Read, Read the string from db as String,

 JSONObject json = new JSONObject(stringreadfromsqlite);
  ArrayList items = json.optJSONArray("uniqueArrays");

To Insert :

ArrayList<String> inputArray=new ArrayList<String>();

Add Values to inputArray

Gson gson = new Gson();

String inputString= gson.toJson(inputArray);

System.out.println("inputString= " + inputString);

Use "inputString" to save the value of ArrayList<String> in SQLite Database

To retreive:

Get the String from the SQLiteDatabse what you saved and changed into ArrayList type like below:

outputarray is a String which is get from SQLiteDatabase for this example.

Type type = new TypeToken<ArrayList<String>>() {}.getType();

ArrayList<String>  finalOutputString = gson.fromJson(outputarray, type);