Base/Core class for Android Developement

activity_dashboard.xml

<?xml version="1.0" encoding="utf-8"?>
<layout xmlns:tools="http://schemas.android.com/tools"
        xmlns:android="http://schemas.android.com/apk/res/android"
        xmlns:app="http://schemas.android.com/apk/res-auto"
        xmlns:bind="http://schemas.android.com/apk/res-auto">

    <data>
            <variable
                name="viewModel"
                type="package_name.DashboardViewModel" />

    </data>
    
               <androidx.recyclerview.widget.RecyclerView
                    android:id="@+id/recycler_dashboard"
                    android:layout_width="match_parent"
                    android:layout_height="match_parent"
                    app:adapter="@{viewModel.adapter}"
                    app:layoutManager="androidx.recyclerview.widget.LinearLayoutManager" />

    </layout>

BaseRecyclerViewAdapter.kt

/**
 * Created By: Rakshit Nawani
 * Date:  January 18 2020
 *
 * BaseRecyclerViewAdapter can be used as a base class for all the Recycler View's Adapter, it contains all the basic functions needed by the user, like
 * 1. Add Item
 * 2. Update Item
 * 3. Add List
 * 4. Remove Item
 * and many more according to needs.
 * 
 */
 
abstract class BaseRecyclerViewAdapter<BD : ViewDataBinding, T>(
    @LayoutRes private var layoutId: Int, var mList: ArrayList<T> = ArrayList()
) :
    RecyclerView.Adapter<BaseRecyclerViewAdapter<BD, T>.BaseRecyclerViewHolder>() {


    override fun onCreateViewHolder(parent: ViewGroup, viewType: Int): BaseRecyclerViewHolder =
        BaseRecyclerViewHolder(
            DataBindingUtil.inflate(
                LayoutInflater.from(parent.context),
                layoutId,
                parent,
                false
            )
        )

    private var baseRecyclerViewItemListener: BaseRecyclerViewItemListener? = null

    fun addItem(t: T, position: Int? = null) {
        when (position) {
            null -> mList.add(t)
            else -> mList.add(position, t)
        }
        notifyItemInserted(position ?: mList.size - 1)
        baseRecyclerViewItemListener?.addItem(position ?: mList.size - 1)
    }

    open fun addItemAtBeginning(t: T) {
        mList.add(0, t)
        notifyItemInserted(0)
    }

    open fun getItem(position: Int): T = mList[position]

    fun findItem(predicate: (T) -> Boolean): T? = mList.find(predicate)

    fun itemPosition(t: T): Int = mList.indexOf(t)

    open fun removeItem(position: Int) {
        if (position < 0) return
        mList.removeAt(position)
        notifyItemRemoved(position)
        baseRecyclerViewItemListener?.removeItem(position)
    }

    fun updateItem(position: Int, t: T) {
        mList[position] = t
        notifyItemChanged(position)
        baseRecyclerViewItemListener?.changeItem(position)
    }

    fun addItems(t: List<T>) {
        mList.addAll(t)
        notifyDataSetChanged()
        baseRecyclerViewItemListener?.addAllItems()
    }

    override fun getItemCount(): Int = mList.size

    fun getAllItems(): ArrayList<T> = mList

    open fun clear() {
        mList.clear()
        notifyDataSetChanged()
    }

    operator fun contains(item: T): Boolean = mList.contains(item)
    fun getPositionForItem(item: T) = when {
        mList.size > 0 -> mList.indexOf(item)
        else -> -1
    }

    fun moveItems(fromPosition: Int, toPosition: Int): Boolean {
        if (fromPosition < toPosition) {
            for (i in fromPosition until toPosition) {
                Collections.swap(mList, i, i + 1)
            }
        } else {
            for (i in fromPosition downTo toPosition + 1) {
                Collections.swap(mList, i, i - 1)
            }
        }
        notifyItemMoved(fromPosition, toPosition)
        return true
    }

    inner class BaseRecyclerViewHolder(var binding: BD) : RecyclerView.ViewHolder(binding.root)
}

BindingActivity.kt

/**
 * Created By: Rakshit Nawani
 * Date:  January 18 2020
 *
 * Binding Activity can be used as a base class for all the activity, it contains all the basic functions needed by the user, like
 * 1. Printing log
 * 2. Displaying Toast
 * 3. Show/Hide Loading
 * and many more according to needs.
 *
 * In an Activity extend it with BindingActivity<Data Binding Class of that class>
 * After extending Activity we need to override methods which is getLayoutResId, implement it like below
 *
 * @LayoutRes
 * override fun getLayoutResId() = R.layout.your_layout_name_here
 *
 *
 */
abstract class BindingActivity<T : ViewDataBinding> : AppCompatActivity() {
    @LayoutRes
    abstract fun getLayoutResId(): Int

    private var loadingDialog: AlertDialog? = null

    protected lateinit var binding: T private set

    override fun onCreate(savedInstanceState: Bundle?) {
        super.onCreate(savedInstanceState)

        //Printling the Class name in logs
        printLog(javaClass.simpleName)

        binding = DataBindingUtil.setContentView(this, getLayoutResId())
    }

    private var toast: Toast? = null
    /**
     * showToast with message
     *  @view: for custom toast provide view perform inflater and other task at your end
     *  @gravity: provide gravity
     */
    fun showToast(
        message: String?,
        view: View? = null,
        duration: Int = Toast.LENGTH_LONG,
        gravity: Int = Gravity.BOTTOM or Gravity.CENTER_VERTICAL, @DimenRes x: Int = 0, @DimenRes y: Int = 0,
        cancelPrevious: Boolean = false
    ) {

        if (cancelPrevious) toast?.cancel()

        // set custom view
        when {
            view != null -> {
                toast = Toast(context)
                toast?.view = view
            }
            else -> toast = Toast.makeText(context, message, duration)
        }
        // set duration
        toast?.duration = duration
        // set position
        var marginY = 0
        var marginX = 0
        if (y != 0) marginY = resources.getDimensionPixelSize(y)
        if (x != 0) marginX = resources.getDimensionPixelSize(x)
        if (marginX > 0 || marginY > 0) toast?.setGravity(gravity, marginX, marginY)
        // show toast
        toast?.show()
    }

    /**
     * For Displaying the loading when an API is hit
     */
    fun showLoading(context: Context) {

        try {
            if (loadingDialog == null) {
                val factory: LayoutInflater = LayoutInflater.from(context)
                val deleteDialogView: View = factory.inflate(R.layout.loading_screen, null)
                loadingDialog =
                    AlertDialog.Builder(context, R.style.AppCompatAlertDialogStyle).create()
                loadingDialog!!.setView(deleteDialogView)
                loadingDialog!!.setCanceledOnTouchOutside(false)
                loadingDialog!!.setCancelable(false)

                hideKeyboard()
            }

            loadingDialog!!.show()
        } catch (e: Exception) {
            e.printStackTrace()
        }
    }

    /**
     * For hiding the loading
     */
   open fun hideLoading() {
        try {
            loadingDialog?.dismiss()
            hideKeyboard()
        } catch (e: Exception) {
            e.printStackTrace()
        }
    }

    /**
     * For Hiding the keyboard
     */
    open fun hideKeyboard() {
        val view = this.currentFocus
        if (view != null) {
            val imm =
                (getSystemService(Context.INPUT_METHOD_SERVICE) as InputMethodManager)
            imm.hideSoftInputFromWindow(view.windowToken, 0)
        }
    }

    /**
     * function to check if internet connection is active or not.
     *
     * @return true if connected to internet else false
     */
    open fun isConnectedToInternet(): Boolean {
        val cm =
            (getSystemService(Context.CONNECTIVITY_SERVICE) as ConnectivityManager)
        val activeNetwork = cm.activeNetworkInfo
        return activeNetwork != null
    }

    open fun printLog(message: String) {
        Log.d(getString(R.string.app_name), message)
    }
}

BindingFragment.kt

/**
 * Created By: Rakshit Nawani
 * Date:  January 18 2020
 *
 * BindingFragment can be used as a base class for all the Fragments, it contains all the basic functions needed by the user 
 * which will be connected with the BindingActivity
 *
 * In a Fragment extend it with BindingFragment<Data Binding Class of that class>
 * After extending Fragment we need to override methods which is getLayoutResId, implement it like below
 *
 * @LayoutRes
 * override fun getLayoutResId() = R.layout.your_layout_name_here
 */
 
abstract class BindingFragment<T : ViewDataBinding> : Fragment() {
    @LayoutRes
    abstract fun getLayoutResId(): Int

    private var loadingDialog: AlertDialog? = null

    protected lateinit var binding: T private set

    override fun onCreateView(
        inflater: LayoutInflater,
        container: ViewGroup?,
        savedInstanceState: Bundle?
    ): View? {

        (activity as BindingActivity<*>).printLog(javaClass.simpleName)

        setHasOptionsMenu(true)

        return DataBindingUtil.inflate<T>(inflater, getLayoutResId(), container, false)
            .apply { binding = this }.root
    }

    private var toast: Toast? = null
    /**
     * showToast with message
     *  @view: for custom toast provide view perform inflater and other task at your end
     *  @gravity: provide gravity
     */
    open fun showToast(
        message: String?,
        view: View? = null,
        duration: Int = Toast.LENGTH_LONG,
        gravity: Int = Gravity.BOTTOM or Gravity.CENTER_VERTICAL, @DimenRes x: Int = 0, @DimenRes y: Int = 0,
        cancelPrevious: Boolean = false
    ) {

        (activity as BindingActivity<*>).showToast(
            message = message,
            view = view,
            duration = duration,
            gravity = gravity,
            cancelPrevious = cancelPrevious
        )
    }

    /**
     * For Displaying the loader
     */
    fun showLoading(context: Context) {

        try {

            (activity as BindingActivity<*>).hideLoading()
            (activity as BindingActivity<*>).showLoading(context)

        } catch (e: Exception) {
            e.printStackTrace()
        }
    }

    /**
     * For hiding the loading
     */
    fun hideLoading() {
        (activity as BindingActivity<*>).hideLoading()
    }
}

dashboard_list_item.xml

<?xml version="1.0" encoding="utf-8"?>
<layout xmlns:android="http://schemas.android.com/apk/res/android"
        xmlns:app="http://schemas.android.com/apk/res-auto">

    <data>
        <variable
                name="data"
                type="String" />
    </data>
    
            <TextView
                    android:text="@{data}"
                    android:id="@+id/tv_hospital_name"
                    android:layout_width="match_parent"
                    android:layout_height="wrap_content"
                    android:textColor="@color/divider_dark" />
    </layout>

DashboardActivity.kt

/**
 * Created By: Rakshit Nawani
 * Date:  January 18 2020
 * 
 * Sample Activity, displays how to use the Base Classes
 *
 */
class DashboardActivity : BindingActivity<ActivityDashboardBinding>() {

@LayoutRes
    override fun getLayoutResId() = R.layout.activity_dashboard
    lateinit var viewModel: DashboardViewModel

 override fun onCreate(savedInstanceState: Bundle?) {
        super.onCreate(savedInstanceState)
     
       //Attaching View Model
        viewModel = DashboardViewModel()
        binding.viewModel = viewModel
        binding.lifecycleOwner = this
     
        //Adding click Listeners for the adapter's item
        viewModel.adapter.listener = object : DashboardAdapter.DataListListener {
            override fun itemClick(data: String) {

              //Calling a function from Base Class
                printlog(data)
            }
         }
   }
}

DashboardAdapter

/**
 * Created By: Rakshit Nawani
 * Date:  January 18 2020
 *
 * Recycler View's Adapter class extending BaseRecyclerViewAdapter<Data_Binding_Class, Model_Type>
 *
 */
class DashboardAdapter: BaseRecyclerViewAdapter<DashboardListItemBinding, String>(R.layout.dashboard_list_item) {

    override fun onBindViewHolder(holder: BaseRecyclerViewHolder, position: Int) {
        holder.binding.data = getItem(position)
        holder.binding.root.setOnClickListener {
            listener?.itemClick(getItem(holder.adapterPosition))
        }
    }

    var listener: DataListListener? = null

    interface DataListListener {
        fun itemClick(data: String)
    }
}

DashboardViewModel.kt

/**
 * Created By: Rakshit Nawani
 * Date:  January 18 2020
 *
 * View Model class for DashboardActivity.kt extending BaseViewModel a core class
 *
 * Displaying how to Add a recycler View Adapter in a View model
 */
 
class DashboardViewModel: BaseViewModel() {
 
 val adapter = DashboardAdapter()
 
 init{
  // Add data in your Adapter
  
   val list = arrayListOf<String>()
      list.add("A")
      list.add("B")
      list.add("C")
      list.add("D")
      list.add("E")
  
  adapter.addItems(list)
  }
}