CDA: Composite Delegate Adapter in Kotlin

CDA Lib is a simple delegate-pattern to build Adapters of the recyclerview in composition instead of inheritance (which is the common way in android to build adatper by extending from Adapter classes). Also the lib includes some convenience methods to easily notify calculate and dispatch updates to the adapters by using the DiffUtils.

Using this libs you should speed up your development and reduce the changes of getting a long classes adapters. With CDA you only concernt about the fact of building the ViewHolders you want to include in the adapter and adding the data that it represents. No switches, not adapters, no need to notify updates manually.

Version 1.0.3

First release of the lib, waiting for feedback. Included:

Composite delegate Adapter CompositeDelegateAdapter
Methods to notify the adapter by using DiffUtils internally
Contract to represent UI models that the adapter will show (RecyclerViewType)

Getting stared

Setting up dependecy

    implementation 'com.github.ingjuanocampo:CompositeDelegateAdapter:XXX'

Please replace the XXX with the latest version.

Also include this into the repositories list

    maven { url 'https://jitpack.io' }

It should ended up looking like this:

allprojects {
     repositories {
         google()
         jcenter()
         maven { url 'https://jitpack.io' }
     }

Terminology

CompositeDelegateAdapter: Is the Adapter you will set to your recyclerview. It receives in the constructos the size of the viewholders your adapter will support as an integer.

        val adapter = CompositeDelegateAdapter(10)

The class extends from the RecyclerView.Adapter and it is open to extension (Please avoid it, keep your adapters easy and clean)

This adapter uses to renderize a lisf of DelegateViewHolder, and you can add them so the CompositeDelegateAdapter.

Use the method appendDelegate(...) to append a DelegateViewHolder, by also including the viewType id that it is related to.

for example;

        adapter.appendDelegate(DelegateViewTypes.COLOR_VIEW_TYPE.ordinal) { ColorItemViewHolder(it) }

RecyclerViewType is a contract interface to bind the items in the adapter to their respective DelegateViewHolder.

interface RecyclerViewType {
    fun getDelegateId(): Int
    fun getViewType(): Int
}

Implement this and provide a unique ID and a viewTypeId both as Integers.

For example;

data class ColorRecyclerViewType(val text: String, val textColor: Int, val bkg: Int):
    RecyclerViewType {
    override fun getDelegateId(): Int {
        return text.hashCode()
    }

    override fun getViewType(): Int = DelegateViewTypes.COLOR_VIEW_TYPE.ordinal
}

Please be aware that the model you will use here should represent what need to be bound into the ViewHolder.

DelegateViewHolder: This class extends from RecyclerView.ViewHolder and is the one in charge of biding the information assigned to RecyclerViewType for the given position.

For example:

data class ColorItemViewHolder( val parent: ViewGroup):
    DelegateViewHolder(LayoutInflater.from(parent.context).inflate(R.layout.delegate_color, parent, false)) {

    private val tvDelegate = itemView.findViewById<TextView>(R.id.tvDelegate)
    private val lnDelegate = itemView.findViewById<LinearLayout>(R.id.lnDelegate)

    override fun onBindViewHolder(recyclerViewType: RecyclerViewType) {
        recyclerViewType as ColorRecyclerViewType
        tvDelegate.text = recyclerViewType.text
        tvDelegate.setTextColor(itemView.resources.getColor(recyclerViewType.textColor))
        lnDelegate.setBackgroundColor(itemView.resources.getColor(recyclerViewType.bkg))
    }

}

Say goodbye to Inheritance Adapter, Say hello to CDA!

Finally, to set items into the adapter, you can just something like this

        val recyclerView = findViewById<RecyclerView>(R.id.recyclerView)
        
        val adapter = CompositeDelegateAdapter(1)

        adapter.appendDelegate(DelegateViewTypes.COLOR_VIEW_TYPE.ordinal) { ColorItemViewHolder(it) }

        recyclerView.adapter = adapter

        adapter.addNewItem(ColorRecyclerViewType(
                "Test 1",
                R.color.white,
                R.color.design_default_color_error
        ))

        adapter.addNewItem(ColorRecyclerViewType(
                "Test 2",
                R.color.black,
                R.color.white
        ))
        adapter.addNewItem(ColorRecyclerViewType(
                "Test 3",
                R.color.purple_200,
                R.color.teal_700
        ))
        adapter.addNewItem(ColorRecyclerViewType(
                "Test 4",
                R.color.design_default_color_primary,
                R.color.design_default_color_secondary
        ))
        adapter.addNewItem(ColorRecyclerViewType(
                "Test 5",
                R.color.material_on_background_disabled,
                R.color.design_default_color_on_secondary
        ))

In the above example, there is only one DelegateViewHolder as the ColorItemViewHolder which shows the info from ColorRecyclerViewType.

The ColorRecyclerViewType uses a simple interger as recycler view type, in this case DelegateViewTypes.COLOR_VIEW_TYPE.ordinal, so as you may observe, the method adapter.appendDelegate(id) { } recieves the same id of the RecyclerViewType that will represent the data. Also the method receives the DelegateViewHolder as a lambda fuction to be executed by the adapter.

Enjoy it! :) and any feedback is welcome!

ingjuanocampo / CompositeDelegateAdapter