Today I Learned

오늘은 Activity챕터의 실습파트인 할일 목록 어플을 만들었다.

할일 목록 앱

화면을 할 일 목록과 등록 액티비티로 구성하고 인텐트로 화면을 전환.
ADD TODO 버튼을 눌러 할일을 추가한 다음 자동으로 목록으로 돌아오게 구성
모든 데이터는 메모리에 저장하고 화면 전환시 데이터가 유지되도록 번들에 저장

실행 결과

• 첫 화면
  

• 할 일 작성
  

• 목록
  

• 화면 회전
  

코드 구현

• MainActivity.kt

class MainActivity : AppCompatActivity() {

    lateinit var binding: ActivityMainBinding
    var datas: MutableList<String>? = null
    lateinit var adapter: MyAdapter

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

        val requestLauncher: ActivityResultLauncher<Intent> = registerForActivityResult(
            ActivityResultContracts.StartActivityForResult()){
            it.data!!.getStringExtra("result")?.let {
                datas?.add(it)
                adapter.notifyDataSetChanged()
            }
        }

        binding.mainFab.setOnClickListener {
            val intent = Intent(this, AddActivity::class.java)
            requestLauncher.launch(intent)
        }

        datas = savedInstanceState?.let {
            it.getStringArrayList("datas")?.toMutableList()
        } ?: let {
            mutableListOf<String>()
        }

        

        val layoutManager = LinearLayoutManager(this)
        binding.mainRecyclerView.layoutManager=layoutManager
        adapter=MyAdapter(datas)
        binding.mainRecyclerView.adapter=adapter
        binding.mainRecyclerView.addItemDecoration(
            DividerItemDecoration(this, LinearLayoutManager.VERTICAL)
        )
    }

    override fun onSaveInstanceState(outState: Bundle) {
        super.onSaveInstanceState(outState)
        outState.putStringArrayList("datas", ArrayList(datas))
    }
    
}

• AddActivity.kt

class AddActivity : AppCompatActivity() {
    lateinit var binding: ActivityAddBinding
    override fun onCreate(savedInstanceState: Bundle?) {
        super.onCreate(savedInstanceState)
        binding= ActivityAddBinding.inflate(layoutInflater)
        setContentView(binding.root)
    }

    override fun onCreateOptionsMenu(menu: Menu?): Boolean {
        menuInflater.inflate(R.menu.menu_add, menu)
        return super.onCreateOptionsMenu(menu)
    }

    override fun onOptionsItemSelected(item: MenuItem): Boolean = when(item.itemId){
        R.id.menu_add_save -> {
            val intent = intent
            intent.putExtra("result", binding.addEditView.text.toString())
            setResult(Activity.RESULT_OK, intent)
            finish()
            true
        }
        else -> true
    }
}

• MyAdapter.kt

class MyViewHolder(val binding: ItemRecyclerviewBinding): RecyclerView.ViewHolder(binding.root)

class MyAdapter(val datas: MutableList<String>?): RecyclerView.Adapter<RecyclerView.ViewHolder>(){

    override fun getItemCount(): Int{
        return datas?.size ?: 0
    }

    override fun onCreateViewHolder(parent: ViewGroup, viewType: Int): RecyclerView.ViewHolder
            = MyViewHolder(ItemRecyclerviewBinding.inflate(LayoutInflater.from(parent.context), parent, false))

    override fun onBindViewHolder(holder: RecyclerView.ViewHolder, position: Int) {
        val binding=(holder as MyViewHolder).binding
        binding.itemData.text= datas!![position]
    }
}

• item_recyclerview.xml

<?xml version="1.0" encoding="utf-8"?>
<LinearLayout
    android:id="@+id/item_root"
    xmlns:android="http://schemas.android.com/apk/res/android"
    android:layout_width="match_parent"
    android:layout_height="wrap_content"
    android:orientation="horizontal"
    android:padding="16dp"
    android:layout_margin="8dp">
    <ImageView
        android:layout_width="wrap_content"
        android:layout_height="wrap_content"
        android:src="@drawable/todo"/>
    <TextView
        android:id="@+id/item_data"
        android:layout_width="0dp"
        android:layout_weight="1"
        android:layout_height="wrap_content"
        android:textStyle="bold"
        android:textSize="16dp"
        android:layout_marginLeft="24dp"
        />
</LinearLayout>