Enhanced Adapter

This is a RecyclerView.Adapter extension which provides the functionality:

• Item sorting; e.g. alphabetically.
• Item filtering; filtering the list based on a search query.
• Item selection; facilitates single & multi-selection of items.
• Uses DiffUtil behind the scenes. This means:
  • Changes in the list are animated (e.g. items slide up when one is removed).
  • Changes are efficient; only changed items are rebound (i.e. no notifyDataSetChanged()).
  • No UI freezes; list change calculations are done in a background thread.

Usage

The library is published to Maven Central, so ensure you have the following in your top-level build.gradle:

allprojects {
    repositories {
        mavenCentral()
    }
}

Add the dependency to your app-level build.gradle:

dependencies {
    implementation 'com.github.mrbean355:enhanced-adapter:1.1.0'
}

Finally, you can create an adapter which extends com.github.mrbean355.android.EnhancedAdapter instead of the usual RecyclerView.Adapter.

Minimal Usage

/** Maximum number of multi-selections allowed. */
private const val MAX_SELECTIONS = 3
/** Callback for calculating the diff between two items in a list. */
private val DIFF_CALLBACKS = MyDiffCallbacks()

class MyAdapter : EnhancedAdapter<MyItem, MyAdapter.MyViewHolder>(DIFF_CALLBACKS, MAX_SELECTIONS) {

    /** Normal onCreateViewHolder() stuff */
    override fun onCreateViewHolder(parent: ViewGroup, viewType: Int): ViewHolder {
        val inflater = LayoutInflater.from(parent.context)
        return ViewHolder(inflater.inflate(android.R.layout.simple_list_item_1, parent, false))
    }

    /** Normal onBindViewHolder() stuff */
    override fun onBindViewHolder(holder: ViewHolder, position: Int) {
        val item = getItemAt(position)
        holder.textView.text = item.name
    }

    /** Normal view holder stuff */
    class MyViewHolder(itemView: View) : RecyclerView.ViewHolder(itemView) {
        val textView: TextView = itemView as TextView
    }

    /**
    * Callback for calculating the diff between two items in a list.
    * 
    * See: https://developer.android.com/reference/androidx/recyclerview/widget/DiffUtil.ItemCallback
    */
    class MyDiffCallbacks : DiffUtil.ItemCallback<MyItem>() {

        override fun areItemsTheSame(oldItem: MyItem, newItem: MyItem): Boolean {
            return oldItem.id == newItem.id
        }

        override fun areContentsTheSame(oldItem: MyItem, newItem: MyItem): Boolean {
            return true
        }
    }
}

Optional Extras

Sorting

class MyAdapter : EnhancedAdapter<MyItem, MyAdapter.MyViewHolder>(MyDiffCallbacks(), 0) {
    // Minimal stuff omitted...
    
    /** Customise how items are compared. */
    override fun compareItems(lhs: MyItem, rhs: MyItem): Int {
        return lhs.name.compareTo(rhs.name)
    }
}

Filtering

class MyAdapter : EnhancedAdapter<MyItem, MyAdapter.MyViewHolder>(MyDiffCallbacks(), 0) {
    // Minimal stuff omitted...
    
    /** Customise how items are tested. */
    override fun testItem(item: MyItem, query: String): Boolean {
        return item.name.contains(query, ignoreCase = true)
    }
}

Single Selection

class MyAdapter : EnhancedAdapter<MyItem, MyAdapter.MyViewHolder>(MyDiffCallbacks(), 0) {
    // Minimal stuff omitted...
    
    override fun onBindViewHolder(holder: ViewHolder, position: Int) {
        holder.itemView.setOnClickListener {
            // Your action here.
        }
    }
}

Multi-selection

class MyAdapter : EnhancedAdapter<MyItem, MyAdapter.MyViewHolder>(MyDiffCallbacks(), 5) {
    // Pass the max number of selection in the constructor (above).
    
    // Minimal stuff omitted...
    
    override fun onBindViewHolder(holder: ViewHolder, position: Int) {
        val isSelected = isItemSelected(position)
        val context = holder.itemView.context
        // Do something to the item to indicate its selection status:
        if (isSelected) {
            holder.itemView.setBackgroundColor(ContextCompat.getColor(context, R.color.colorAccent))
        } else {
            holder.itemView.setBackgroundColor(ContextCompat.getColor(context, R.color.transparent))
        }
        holder.itemView.setOnClickListener {
            // Notify that an item has been selected/unselected:
            onItemClicked(holder.adapterPosition)
        }
    }
}