Navigation safe args

1. safe args 란?

여러가지 데이터 전달 방법이 있는 상황에서 데이터 전달의 한 방법이라고 보시면 될 것 같습니다.

2. safe args 사용 예제

1. nav_graph.xml

<?xml version="1.0" encoding="utf-8"?>
<navigation 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:id="@+id/nav_graph"
    app:startDestination="@id/FirstFragment">

    <fragment
        android:id="@+id/FirstFragment"
        android:name="com.project.safeargs.FirstFragment"
        android:label="@string/hello_blank_fragment"
        tools:layout="@layout/fragment_first">

        <action
            android:id="@+id/action_FirstFragment_to_SecondFragment"
            app:destination="@id/SecondFragment" />

    </fragment>

    <fragment
        android:id="@+id/SecondFragment"
        android:name="com.project.safeargs.SecondFragment"
        android:label="@string/hello_blank_fragment"
        tools:layout="@layout/fragment_second">

        <action
            android:id="@+id/action_SecondFragment_to_FirstFragment"
            app:destination="@id/FirstFragment" />

        <argument
            android:name="item"
            app:argType="com.project.safeargs.Item[]" />

    </fragment>
</navigation>

쪽 코드를 보시면 Item[]이라고 타입을 지정해주는 것을 확인할 수 있습니다. 타입은 Item 객체의 배열 타입이 됩니다.

2. FirstFragment.kt

class FirstFragment : Fragment() {

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

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

        val item = ArrayList<Item>()
        item.add(Item(111, "changed"))

        view.findViewById<Button>(R.id.button_first).setOnClickListener {
            val action = FirstFragmentDirections.actionFirstFragmentToSecondFragment(item.toTypedArray())

            findNavController().navigate(action)
        }
    }
}

3. SecondFragment.kt

class SecondFragment : Fragment() {

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

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

        val args: SecondFragmentArgs by navArgs()
        val itemList = args.item.toCollection(ArrayList())

        view.findViewById<TextView>(R.id.textview_second).text = "${itemList[0].id} ${itemList[0].name}"
        view.findViewById<Button>(R.id.button_second).setOnClickListener {
            findNavController().navigate(R.id.action_SecondFragment_to_FirstFragment)
        }
    }
}

val args: SecondFragmentArgs by navArgs() 를 통해서 xml 작성된 argument 에 대한 클래스가 자동으로 생성이 되고, 받아 오게 됩니다.

safe args는 네이게이션 AAC를 사용할 때 프레그먼트와 데이터 전송까지 한번에 관리하게 용의한 방법으로 볼 수 있습니다.

코드 확인 : https://github.com/ilil1/safeargs

3. reference

https://developer.android.com/guide/navigation/navigation-pass-data?hl=ko