Fragments en Kotlin

manejo de fragments en Kotlin

Fragments

Crear el proyecto FragmentExample

build.gradle

buildFeatures {
    viewBinding = true
}

colors.xml

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

    <color name="blue">#80D8FF</color>
    <color name="red">#FF80AB</color>

    <color name="purple">#673AB7</color>
</resources>

creación de los 2 fragments

fragment_red.xml

<?xml version="1.0" encoding="utf-8"?>
<FrameLayout
    xmlns:android="http://schemas.android.com/apk/res/android"
    android:layout_width="match_parent"
    android:layout_height="match_parent"
    android:background="@color/red">

    <Button
        android:id="@+id/btnPlus"
        android:text="+1"
        android:layout_gravity="center"
        android:background="@color/red"
        android:layout_width="wrap_content"
        android:layout_height="wrap_content"/>

</FrameLayout>

fragment_blue.xml

<?xml version="1.0" encoding="utf-8"?>
<FrameLayout
    xmlns:android="http://schemas.android.com/apk/res/android"
    android:layout_width="match_parent"
    android:layout_height="match_parent"
    android:background="@color/blue">

    <Button
        android:id="@+id/btnPlus"
        android:text="+1"
        android:layout_gravity="center"
        android:background="@color/blue"
        android:layout_width="wrap_content"
        android:layout_height="wrap_content"/>

</FrameLayout>

OnFragmentActionsListener.kt

interface OnFragmentActionsListener {
    fun onClickFragmentButton()
}

RedFragment.kt

class RedFragment : Fragment() {
    private lateinit var _binding: FragmentRedBinding
    private val binding get() = _binding

    private lateinit var listener: OnFragmentActionsListener

    override fun onAttach(context: Context) {
        super.onAttach(context)
        if (context is OnFragmentActionsListener) {
            listener = context
        }
    }

    override fun onCreateView(
        inflater: LayoutInflater, container: ViewGroup?,
        savedInstanceState: Bundle?
    ): View? {
        _binding = FragmentRedBinding.inflate(inflater, container, false)
        return binding.root
    }

    override fun onViewCreated(view: View, savedInstanceState: Bundle?) {
        super.onViewCreated(view, savedInstanceState)

        // view binding in fragment
        binding.btnPlus.setOnClickListener { listener.onClickFragmentButton() }
    }

    override fun onDetach() {
        super.onDetach()
        // listener = null
        binding.btnPlus.setOnClickListener {  }
    }
}

BlueFragment.kt

class BlueFragment : Fragment() {

    private lateinit var _binding: FragmentBlueBinding
    private val binding get() = _binding

    private lateinit var listener: OnFragmentActionsListener

    override fun onAttach(context: Context) {
        super.onAttach(context)
        if (context is OnFragmentActionsListener) {
            listener = context
        }
    }

    override fun onCreateView(
        inflater: LayoutInflater, container: ViewGroup?,
        savedInstanceState: Bundle?
    ): View? {
        _binding = FragmentBlueBinding.inflate(inflater, container, false)
        return binding.root
    }

    override fun onViewCreated(view: View, savedInstanceState: Bundle?) {
        super.onViewCreated(view, savedInstanceState)

        //btnPlus = requireView().findViewById(R.id.btnPlus)
        binding.btnPlus.setOnClickListener { listener.onClickFragmentButton() }
    }

    override fun onDetach() {
        super.onDetach()
        // listener = null
        binding.btnPlus.setOnClickListener { }
    }
}

activity_main.xml

<?xml version="1.0" encoding="utf-8"?>
<LinearLayout
    xmlns:android="http://schemas.android.com/apk/res/android"
    android:orientation="horizontal"
    android:layout_width="match_parent"
    android:layout_height="match_parent">
    <fragment
        android:name="com.example.fragmentexample.RedFragment"
        android:id="@+id/first"
        android:layout_weight="1"
        android:layout_width="0dp"
        android:layout_height="match_parent" />
    <fragment
        android:name="com.example.fragmentexample.BlueFragment"
        android:id="@+id/second"
        android:layout_weight="1"
        android:layout_width="0dp"
        android:layout_height="match_parent" />
</LinearLayout>

MainActivity.kt

class MainActivity : AppCompatActivity(), OnFragmentActionsListener {
    private lateinit var binding: ActivityMainBinding


    override fun onCreate(savedInstanceState: Bundle?) {
        super.onCreate(savedInstanceState)
        // setContentView(R.layout.activity_main)
        binding = ActivityMainBinding.inflate(layoutInflater)
        setContentView(binding.root)

    }


    override fun onClickFragmentButton() {
        Toast.makeText(this, "El botón ha sido pulsado", Toast.LENGTH_SHORT).show()
    }
}

activity_main.xml

<?xml version="1.0" encoding="utf-8"?>
<LinearLayout
    xmlns:android="http://schemas.android.com/apk/res/android"
    android:layout_width="match_parent"
    android:layout_height="match_parent"
    android:background="@color/purple"
    android:orientation="vertical">

    <Button
        android:id="@+id/btnRed"
        android:layout_width="wrap_content"
        android:layout_height="wrap_content"
        android:layout_gravity="center_horizontal"
        android:padding="8dp"
        android:layout_margin="5dp"
        android:background="@color/red"
        android:text="Fragment rojo" />

    <Button
        android:id="@+id/btnBlue"
        android:layout_width="wrap_content"
        android:layout_height="wrap_content"
        android:padding="8dp"
        android:layout_gravity="center_horizontal"
        android:layout_margin="5dp"
        android:background="@color/blue"
        android:text="Fragment azul" />

    <FrameLayout
        android:id="@+id/fragmentContainer"
        android:layout_width="match_parent"
        android:layout_height="match_parent" />
</LinearLayout>

MainActivity.kt

class MainActivity : AppCompatActivity(), OnFragmentActionsListener {
    private lateinit var binding: ActivityMainBinding

    override fun onCreate(savedInstanceState: Bundle?) {
        super.onCreate(savedInstanceState)
        // setContentView(R.layout.activity_main)
        binding = ActivityMainBinding.inflate(layoutInflater)
        setContentView(binding.root)

        // replaceFragment(RedFragment())

        binding.btnRed.setOnClickListener { replaceFragment(RedFragment()) }
        binding.btnBlue.setOnClickListener { replaceFragment(BlueFragment()) }
    }

    private fun replaceFragment(fragment: Fragment){
        val fragmentTransaction = supportFragmentManager.beginTransaction()
        fragmentTransaction.replace(binding.fragmentContainer.id, fragment)
        fragmentTransaction.addToBackStack(null)
        fragmentTransaction.commit()
    }

    override fun onClickFragmentButton() {
        Toast.makeText(this, "El botón ha sido pulsado", Toast.LENGTH_SHORT).show()
    }
}