Fragments en Kotlin

Uso de fragments en Kotlin

Repositorio en Github

Ejercicio: Fragments con Recyclerview

Crear el proyecto

Añadir dependencias en build.gradle

implementation("androidx.navigation:navigation-fragment:2.7.5")
implementation("androidx.navigation:navigation-ui:2.7.5")
implementation("androidx.recyclerview:recyclerview:1.3.2")

colors.xml

<?xml version="1.0" encoding="utf-8"?>
<resources>
    <color name="black">#FF000000</color>
    <color name="white">#FFFFFFFF</color>
</resources>

dimens.xml

<resources>
    <dimen name="fab_margin">16dp</dimen>
    <dimen name="text_margin">16dp</dimen>
</resources>

strings.xml

<resources>
    <string name="app_name">Cars</string>
    <!-- TODO: Remove or change this placeholder text -->
    <string name="hello_blank_fragment">Hello blank fragment</string>
    <string name="title_activity_main2">MainActivity</string>
    <!-- Strings used for fragments for navigation -->
    <string name="first_fragment_label">First Fragment</string>
    <string name="second_fragment_label">Second Fragment</string>
    <string name="next">Next</string>
    <string name="previous">Previous</string>

    <string name="hello_first_fragment">Hello first fragment</string>
    <string name="hello_second_fragment">Hello second fragment. Arg: %1$s</string>
</resources>

data class DataModel.kt

data class DataModel (
    var title : String
)

fragment_main.xml

<?xml version="1.0" encoding="utf-8"?>
<FrameLayout xmlns:android="http://schemas.android.com/apk/res/android"
    xmlns:tools="http://schemas.android.com/tools"
    android:layout_width="match_parent"
    android:layout_height="match_parent"
    tools:context=".MainFragment">

    <!-- TODO: Update blank fragment layout -->
    <androidx.recyclerview.widget.RecyclerView
        android:id="@+id/recyclerView"
        android:layout_width="match_parent"
        android:layout_height="wrap_content"
         />

</FrameLayout>

MainFragment.kt

/**
 * A simple [Fragment] subclass.
 * Use the [MainFragment.newInstance] factory method to
 * create an instance of this fragment.
 */
class MainFragment : Fragment(), ItemClickListener {

    private lateinit var adapter : RecyclerViewAdapter
    private val list = ArrayList<DataModel>()

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

    override fun onCreateView(
        inflater: LayoutInflater, container: ViewGroup?,
        savedInstanceState: Bundle?
    ): View? {
        // Inflate the layout for this fragment
        val view = inflater.inflate(R.layout.fragment_main, container, false)
        buildListData()
        initRecyclerView(view)
        return view
    }

    private fun initRecyclerView(view: View) {
        val recyclerView = view.findViewById<RecyclerView>(R.id.recyclerView)
        val layoutManager = LinearLayoutManager(activity)
        recyclerView.layoutManager = layoutManager
        adapter = RecyclerViewAdapter(list, this)
        recyclerView.adapter = adapter

        //right swipe on recyclerview
        val itemSwipe =  object : ItemTouchHelper.SimpleCallback(0, ItemTouchHelper.RIGHT) {
            override fun onMove(
                recyclerView: RecyclerView,
                viewHolder: RecyclerView.ViewHolder,
                target: RecyclerView.ViewHolder
            ): Boolean {
                //TODO("Not yet implemented")
                return false
            }

            override fun onSwiped(viewHolder: RecyclerView.ViewHolder, direction: Int) {
                showDialog(viewHolder)
            }
        }

        val swap = ItemTouchHelper(itemSwipe)
        swap.attachToRecyclerView(recyclerView)
    }

    private fun showDialog(viewHolder: RecyclerView.ViewHolder) {
        val builder = AlertDialog.Builder(activity)
        builder.setTitle("Delete Item")
        builder.setMessage("Are you sure to delete the item?")
        builder.setPositiveButton("Confirm") {dialog, which ->
            val position = viewHolder.adapterPosition
            list.removeAt(position)
            adapter.notifyItemRemoved(position)
        }
        builder.setNegativeButton("Cancel") {dialog, which ->
            val position = viewHolder.adapterPosition
            adapter.notifyItemChanged(position)
        }
        builder.show()

    }

    private fun buildListData() {
        list.add(DataModel("BMW"))
        list.add(DataModel("Audi"))
        list.add(DataModel("Chevrolet"))
        list.add(DataModel("Ford"))
        list.add(DataModel("Honda"))
        list.add(DataModel("Ferrari"))
    }

    override fun onItemClick(dataModel: DataModel) {
        val fragment: Fragment = DetailFragment.newInstance(dataModel.title)
        val transaction = activity?.supportFragmentManager!!.beginTransaction()

        // transaction.replace(R.id.frame_container, fragment, "detail_fragment");
        transaction.hide(activity?.supportFragmentManager?.findFragmentByTag("main_fragment")!!)
        transaction.add(R.id.frame_container, fragment)
        transaction.addToBackStack(null)
        transaction.commit()
    }

    companion object {
        /**
         * Use this factory method to create a new instance of
         * this fragment using the provided parameters.
         *
         * @return A new instance of fragment MainFragment.
         */
        // TODO: Rename and change types and number of parameters
        fun newInstance(): MainFragment {
            return MainFragment()
        }
    }
}

recycler_row.xml

<?xml version="1.0" encoding="utf-8"?>
<androidx.constraintlayout.widget.ConstraintLayout xmlns:android="http://schemas.android.com/apk/res/android"
    android:layout_width="match_parent"
    android:layout_height="wrap_content"
    xmlns:app="http://schemas.android.com/apk/res-auto">


    <TextView android:id="@+id/titleTextView"
        android:layout_width="wrap_content"
        android:layout_height="wrap_content"
        app:layout_constraintStart_toStartOf="parent"
        app:layout_constraintTop_toTopOf="parent"
        android:layout_margin="20dp"
        android:textSize="30sp"
        android:textStyle="bold"
        android:textColor="#000000"
        />

</androidx.constraintlayout.widget.ConstraintLayout>

RecyclerViewAdapter.kt

class RecyclerViewAdapter(
    private val list: List<DataModel>,
    private val clickListener: ItemClickListener
) : RecyclerView.Adapter<MyViewHolder>() {
    override fun onCreateViewHolder(parent: ViewGroup, viewType: Int): MyViewHolder {
        val view = LayoutInflater.from(parent.context).inflate(R.layout.recycler_row, parent, false)
        return MyViewHolder(view)
    }

    override fun onBindViewHolder(holder: MyViewHolder, position: Int) {
        holder.titleTextView.text = list.get(position).title
        holder.itemView.setOnClickListener(View.OnClickListener {
            clickListener.onItemClick(
                list[position]
            )
        })
    }

    override fun getItemCount(): Int {
        return list.size
    }

    inner class MyViewHolder(view: View) : RecyclerView.ViewHolder(view) {
        var titleTextView: TextView

        init {
            titleTextView = view.findViewById(R.id.titleTextView)
        }
    }

    interface ItemClickListener {
        fun onItemClick(dataModel: DataModel)
    }
}

fragment_detail.xml

<?xml version="1.0" encoding="utf-8"?>
<androidx.constraintlayout.widget.ConstraintLayout xmlns:android="http://schemas.android.com/apk/res/android"
    xmlns:tools="http://schemas.android.com/tools"
    android:layout_width="match_parent"
    android:layout_height="match_parent"
    xmlns:app="http://schemas.android.com/apk/res-auto"
    tools:context=".DetailFragment">

    <!-- TODO: Update blank fragment layout -->
    <TextView android:id="@+id/titleTV"
        android:layout_width="wrap_content"
        android:layout_height="wrap_content"
        app:layout_constraintStart_toStartOf="parent"
        android:textStyle="bold"
        android:textSize="45sp"
        app:layout_constraintEnd_toEndOf="parent"
        app:layout_constraintTop_toTopOf="parent"
        app:layout_constraintBottom_toBottomOf="parent"
        android:text="@string/hello_blank_fragment" />

</androidx.constraintlayout.widget.ConstraintLayout>

DetailFragment.kt

class DetailFragment : Fragment() {
    // TODO: Rename and change types of parameters
    private var mParam1: String? = null
    override fun onCreate(savedInstanceState: Bundle?) {
        super.onCreate(savedInstanceState)
        if (arguments != null) {
            mParam1 = arguments?.getString(ARG_PARAM1)
        }
    }

    override fun onCreateView(
        inflater: LayoutInflater, container: ViewGroup?,
        savedInstanceState: Bundle?
    ): View? {
        // Inflate the layout for this fragment
        val view = inflater.inflate(R.layout.fragment_detail, container, false)
        val titleTV = view.findViewById<TextView>(R.id.titleTV)
        titleTV.text = mParam1
        return view
    }

    companion object {
        // TODO: Rename parameter arguments, choose names that match
        // the fragment initialization parameters, e.g. ARG_ITEM_NUMBER
        private const val ARG_PARAM1 = "param1"

        /**
         * Use this factory method to create a new instance of
         * this fragment using the provided parameters.
         *
         * @param param1 Parameter 1.
         * @return A new instance of fragment DetailFragment.
         */
        // TODO: Rename and change types and number of parameters
        fun newInstance(param1: String?): DetailFragment {
            val fragment = DetailFragment()
            val args = Bundle()
            args.putString(ARG_PARAM1, param1)
            fragment.arguments = args
            return fragment
        }
    }
}

activity_main.xml

<?xml version="1.0" encoding="utf-8"?>
<androidx.constraintlayout.widget.ConstraintLayout xmlns:android="http://schemas.android.com/apk/res/android"
    xmlns:app="http://schemas.android.com/apk/res-auto"
    xmlns:tools="http://schemas.android.com/tools"
    android:layout_width="match_parent"
    android:layout_height="match_parent"
    tools:context=".MainActivity">

    <LinearLayout android:id="@+id/frame_container"
        android:layout_width="match_parent"
        android:layout_height="match_parent"
        app:layout_constraintStart_toStartOf="parent"
        app:layout_constraintEnd_toEndOf="parent"
        app:layout_constraintTop_toTopOf="parent"
        app:layout_constraintBottom_toBottomOf="parent"
        android:orientation="vertical"
        />
</androidx.constraintlayout.widget.ConstraintLayout>

MainActivity.kt

class MainActivity : AppCompatActivity() {
    override fun onCreate(savedInstanceState: Bundle?) {
        super.onCreate(savedInstanceState)
        setContentView(R.layout.activity_main)


        val fragment: Fragment = MainFragment.newInstance()
        val transaction = supportFragmentManager.beginTransaction()
        transaction.replace(R.id.frame_container, fragment, "main_fragment")
        transaction.commit()
    }
}