I have a cart which stores data in Room Database. ...

# android

[Arslan Mushtaq]

I have a cart which stores data in Room Database. How is it possible for me to automatically update my Grand Total when an item Sub Total is changed within the Cart? I’m using the following SQLite functions:

@Query("SELECT * FROM cart_table")
fun getAllItemsFromCart(): LiveData<List<Cart>>

@Insert(onConflict = OnConflictStrategy.REPLACE)
suspend fun insert(cart: Cart)

@Query("DELETE FROM cart_table")
suspend fun deleteAllItemsFromCart()

@Delete
suspend fun deleteItemFromCart(cart: Cart)

@Query("SELECT COUNT(*) FROM cart_table")
suspend fun itemCount(): Int

@Query("SELECT SUM(total) FROM cart_table")
fun getGrandTotal(): LiveData<Double>

@Query("UPDATE cart_table SET quantity = quantity + 1 WHERE id = :id")
suspend fun increaseQuantity(id: Int)

@Query("UPDATE cart_table SET quantity = quantity - 1 WHERE id = :id")
suspend fun decreaseQuantity(id: Int)

[Ahmed Ibrahim]

I think you've already achieved that in this method

@Query("SELECT SUM(total) FROM cart_table")
fun getGrandTotal(): LiveData<Double>

Once the cart_table gets updated the LiveData will emit a new grand total.

[Arslan Mushtaq]

But it isn’t being called when I update the quantity from my RecyclerView Adapter

[Ahmed Ibrahim]

Your Dao looks fine to me, so I'd advice you to put break points inside the Dao's generated code and see if they behave correctly.

[Arslan Mushtaq]

Yes, they work fine. Initially when I call getGrandTotal() in my Fragment. It works but when I try to call it from my adapter. It’s not updating the result.

[Ahmed Ibrahim]

How are your listening to the livedata inside the adapter?

[Arslan Mushtaq]

Solved it using the @Update Annotation.