Added possibility to get view types from the adapter to add support for GridLayoutManager.SpanSizeLookup

[meruiden]

Example usage:

private val loadingIndicatorType = adapter.getItemViewTypeFromClass(LoadingIndicator::class.java)

override fun getSpanSize(position: Int): Int {
    val itemType = adapter.getItemViewType(position)

    return if(itemType == loadingIndicatorType) {
        spanCount
    } else {
        1
    }
}

See #15

[idanatz]

Thanks for the PR!
Please see my comments

[idanatz]

What is the reason for this change?
Each item type the adapter holds must implement Diffable, it doesn't matter if its an internal holder type or external class from the user.

[meruiden]

The reason I changed this is to allow calling the function like this:

getCreatorUniqueIndex(LoadingIndicator::class.java)

When the type is < Diffable > rather then <*> the compiler complains that LoadingIndicator is not a Diffable even though it is. This does work with instances but not when using LoadingIndicator::class.java. You could do a runtime check maybe and throw if it doesn't inherit from Diffable.

[idanatz]

ViewHolderCreatorsStore is an internal class of the library, it should not be used with classes other than DIffable.

The way i see it, the function on OneAdapter.kt can be called with type < * >, but inside InternalAdapter, the function getItemViewTypeFromClass will validate the class if it is of type DIffable (using the Validator class) and throw a new exception (that will be written in the Exceptions.kt)

class UnsupportedClassException(msg: String = "Class must implement Diffable interface") : Throwable(msg)

[meruiden]

I pushed the changes, let me know what u think :)

[idanatz]

change to Class < Diffable > for the reason written in
ViewHolderCreatorsStore.kt

[idanatz]

and place it below
fun getItemViewType

[idanatz]

change to Class < Diffable > for the reason written in
ViewHolderCreatorsStore.kt

[idanatz]

and place these functions at the end of the file

[idanatz]

Looks good.

a couple of final thins:

1. Before addressing the next bullets, pull from develop branch, I've made local changes before your PR and pushed them a few hours ago, after that address the issues below.

2. I know I wrote it but on seconds thought, change
   class UnsupportedClassException(msg: String = "Class must implement Diffable interface") : Throwable(msg)
   to
   class UnsupportedClassException(msg: String = "") : Throwable(msg)
   and move the msg "Class must implement Diffable interface" to the throw site.
   it's more understandable when reading the code to see the actual message.

3. Why is
   fun getItemViewTypeFromClass(clazz: Class<*>): Int?
   returning Int? ? getCreatorUniqueIndex returns Int, it will never be nullable.

4. add this documentation below
   /**

   • Retrieves the view type of an item with a given class.
   • Note that this class must implement the Diffable interface and the adapter must contain items of that class.
   • @throws UnsupportedClassException if the class does not implement the Diffable interface.
     /
     fun getItemViewTypeFromClass(clazz: Class<>): Int?

Note that there are some validations that need to be implemented now that the getItemViewType and getCreatorUniqueIndex are publicly accessible, but I will add them after this PR will be merged.

[meruiden]

Why is
fun getItemViewTypeFromClass(clazz: Class<*>): Int?
returning Int? ? getCreatorUniqueIndex returns Int, it will never be nullable.

Whoops that shouldn't be nullable indeed. I'll remove this

[meruiden]

Looks good.

a couple of final thins:

1. Before addressing the next bullets, pull from develop branch, I've made local changes before your PR and pushed them a few hours ago, after that address the issues below.

2. I know I wrote it but on seconds thought, change
   class UnsupportedClassException(msg: String = "Class must implement Diffable interface") : Throwable(msg)
   to
   class UnsupportedClassException(msg: String = "") : Throwable(msg)
   and move the msg "Class must implement Diffable interface" to the throw site.
   it's more understandable when reading the code to see the actual message.

3. Why is
   fun getItemViewTypeFromClass(clazz: Class<*>): Int?
   returning Int? ? getCreatorUniqueIndex returns Int, it will never be nullable.

4. add this documentation below
   /**

   • Retrieves the view type of an item with a given class.
   • Note that this class must implement the Diffable interface and the adapter must contain items of that class.
   • @throws UnsupportedClassException if the class does not implement the Diffable interface.
     /
     fun getItemViewTypeFromClass(clazz: Class<>): Int?

Note that there are some validations that need to be implemented now that the getItemViewType and getCreatorUniqueIndex are publicly accessible, but I will add them after this PR will be merged.

I pulled the latest changes from develop and changed the stuff you requested, merged all in to master and pushed.

[idanatz]

merged your PR, thanks!
will be released as a minor version in a few days after il check everything is good.