SharedPreferences 실제로 사용하기.

1. main.xml 그리기

<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">

    <EditText
        android:id="@+id/editTxt"
        android:layout_width="wrap_content"
        android:layout_height="wrap_content"
        android:textSize="24sp"
        android:textColor="@color/black"
        android:ems="10"
        android:inputType="textPersonName"
        app:layout_constraintBottom_toBottomOf="parent"
        app:layout_constraintEnd_toEndOf="parent"
        app:layout_constraintStart_toStartOf="parent"
        app:layout_constraintTop_toTopOf="parent" />

    <Button
        android:id="@+id/saveBtn"
        android:layout_width="wrap_content"
        android:layout_height="wrap_content"
        android:layout_marginTop="32dp"
        android:text="저장하기"
        app:layout_constraintEnd_toEndOf="parent"
        app:layout_constraintStart_toStartOf="parent"
        app:layout_constraintTop_toBottomOf="@+id/editTxt" />
</androidx.constraintlayout.widget.ConstraintLayout> 

2.MainActivity 코딩

import androidx.appcompat.app.AppCompatActivity
import android.os.Bundle
import android.widget.Toast
import com.example.sharedpreferences.databinding.ActivityMainBinding

class MainActivity : AppCompatActivity() {
    lateinit var binding : ActivityMainBinding
    override fun onCreate(savedInstanceState: Bundle?) {
        super.onCreate(savedInstanceState)
        binding = ActivityMainBinding.inflate(layoutInflater)
        val  view = binding.root
        setContentView(view)

        binding.saveBtn.setOnClickListener {

            saveData()
            Toast.makeText(this,"데이터가 저장 되었습니다.",Toast.LENGTH_SHORT).show()
        }
        loadData()
    }

    private fun saveData() {

        val pref = getSharedPreferences("pref",0)
        val edit = pref.edit()  //수정 모드
        // 1번째 인자는 키 , 2번째 인자는 실제 담아둘 값
        edit.putString("name",binding.editTxt.text.toString())
        edit.apply() //저장 완료
    }

    private fun loadData() {
        val pref = getSharedPreferences("pref" , 0)
        // 1번째 인자는 키, 2번째 인자는 데이터가 존재하지 않을 경우의 값
        binding.editTxt.setText(pref.getString("name",""))
    }
}

• device file exploer 들어가서 데이터 저장된거 확인가능!