SQLite PRIMARY key AutoIncrement doesn't work

Question

I'm trying to a have a table with an auto incremented primary key. The SQL query for table creation is included.
Problem is the auto-increment does not work. Meaning when I insert a row with NULL as the value of conversation_id it just inserts null. I have this problem on multiple tables.

-- Table: conversations
CREATE TABLE conversations (
    conversation_id INTEGER (64) PRIMARY KEY
                                 UNIQUE,
    target_id       BIGINT (64),
    sender_id       BIGINT (64),
    status          STRING (16)  NOT NULL
                                 DEFAULT unseen,
    is_group        INTEGER (1)  NOT NULL
                                 DEFAULT (0),
    last_update     INTEGER (32) DEFAULT (0),
    target_name     STRING (64),
    target_photo    STRING (256),
    unread_count    INTEGER (10) DEFAULT (0),
    last_message    STRING (256) 
);

The following is the method I use to insert into table:

public Conversation addConversation(Conversation conversation) {
        SQLiteDatabase db = getWritableDatabase();
        ContentValues row = new ContentValues();

        row.put("target_id", conversation.getTargetID());
        row.put("sender_id", conversation.getSenderID());
        row.put("target_name", conversation.getTargetName());
        row.put("target_photo", conversation.getTargetPhoto());
        row.put("status", conversation.getStatus());
        row.put("unread_count", conversation.getUnreadCount());
        row.put("last_message", conversation.getLastMessage());

        conversation.setConversationID(db.insert(TBL_CONVERSATIONS, null, row));
        Log.d(TAG, "conversation added: "+conversation.getConversationID());

        db.close();

        return conversation;
    }

The curious thing here is when I retrieve the insert id from insert method it returns the correct value, but the actual database field is null.

If I understand correctly A column declared INTEGER PRIMARY KEY will autoincrement. [Cite]

Answer 1

From documentation:

A table created using CREATE TABLE AS has no PRIMARY KEY and no constraints of any kind. The default value of each column is NULL.

You don't have to add UNIQUE constraint on a COLUMN that has PRIMARY KEY constraint.
Explanation:

A UNIQUE constraint is similar to a PRIMARY KEY constraint, except that a single table may have any number of UNIQUE constraints.

Instead add NOT NULL. This is why:

According to the SQL standard, PRIMARY KEY should always imply NOT NULL. Unfortunately, due to a bug in some early versions, this is not the case in SQLite. Unless the column is an INTEGER PRIMARY KEY or the table is a WITHOUT ROWID table or the column is declared NOT NULL, SQLite allows NULL values in a PRIMARY KEY column. SQLite could be fixed to conform to the standard, but doing so might break legacy applications. Hence, it has been decided to merely document the fact that SQLite allowing NULLs in most PRIMARY KEY columns.

I recommend using this Column definition:

CREATE TABLE conversations (
    conversation_id INTEGER PRIMARY KEY NOT NULL AUTOINCREMENT,
...
}