[Android] 11. Life Cycle : onCreate, onStart, onResume, onPause, onStop, onDestroy, 데이터 저장, 불러오기

https://github.com/upcake/Class_Examples

교육 중에 작성한 예제들은 깃허브에 올려두고 있습니다. 

gif 파일은 클릭해서 보는 것이 정확합니다.

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 - Life Cycle : onCreate, onStart, onResume, onPause, onStop, onDestroy, 데이터 저장, 불러오기 -

▲Life Cycle 작동 화면

 

▼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">

    <Button
        android:id="@+id/btnMain"
        android:layout_width="wrap_content"
        android:layout_height="wrap_content"
        android:layout_marginTop="164dp"
        android:text="새 창 띄우기"
        android:textSize="24sp"
        app:layout_constraintEnd_toEndOf="parent"
        app:layout_constraintHorizontal_bias="0.466"
        app:layout_constraintStart_toStartOf="parent"
        app:layout_constraintTop_toTopOf="parent" />
</androidx.constraintlayout.widget.ConstraintLayout>

 

▼MainActivity.java

package com.example.my12_lifecycle;

import androidx.appcompat.app.AppCompatActivity;

import android.app.Activity;
import android.content.Intent;
import android.content.SharedPreferences;
import android.os.Bundle;
import android.util.Log;
import android.view.View;
import android.widget.Button;

public class MainActivity extends AppCompatActivity {
    private static final String TAG = "MainActivity";

    @Override
    protected void onCreate(Bundle savedInstanceState) {
        super.onCreate(savedInstanceState);
        setContentView(R.layout.activity_main);
        Log.d(TAG, "onCreate : 호출됨");

        //버튼을 누르면 서브1액티비티가 나오게끔 설정
        Button btnMain = findViewById(R.id.btnMain);
        btnMain.setOnClickListener(new View.OnClickListener() {
            @Override
            public void onClick(View v) {
                Intent intent = new Intent(getApplicationContext(), Sub1Activity.class);
                startActivity(intent);
            }
        });
    }

    //우클릭 - Generate... - Override Methods...
    //실행 하면 onCreate - onStart - onResume
    //메인 버튼 누르면 onPause - onStop
    //서브 버튼 누르면 onRestart - onStart - onResume
    //뒤로가기 누르면 onPuase - onStop - onDestroy
    @Override
    protected void onStart() {
        super.onStart();
        Log.d(TAG, "onStart : 호출됨");
    }

    @Override
    protected void onResume() {
        super.onResume();
        Log.d(TAG, "onResume : 호출됨");
        loadPersonal();
    }

    @Override
    protected void onStop() {
        super.onStop();
        Log.d(TAG, "onStop : 호출됨");
        savePersonal();
    }

    @Override
    protected void onDestroy() {
        super.onDestroy();
        Log.d(TAG, "onDestroy : 호출됨");
    }

    @Override
    protected void onPause() {
        super.onPause();
        Log.d(TAG, "onPause : 호출됨");
    }

    @Override
    protected void onRestart() {
        super.onRestart();
        Log.d(TAG, "onRestart : 호출됨");
    }

    //데이터 저장하기 : onStop
    public void savePersonal() {
        SharedPreferences pref = getSharedPreferences("personal", Activity.MODE_PRIVATE);
        SharedPreferences.Editor editor = pref.edit();
        editor.putString("id", "hong_gil_dong");
        editor.putInt("pw", 1234);
        editor.commit();
    }
    //저장된 데이터 불러오기 : onResume
    public void loadPersonal() {
        SharedPreferences pref = getSharedPreferences("personal", Activity.MODE_PRIVATE);
        if (pref != null) {
            String id = pref.getString("id", "CSS");
            int pw = pref.getInt("pw", 0);

            Log.d(TAG, "loadPersonal: " + id + ", " + pw);
        }
    }
}

 

▼activity_sub1.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=".Sub1Activity">

    <Button
        android:id="@+id/btnSub"
        android:layout_width="wrap_content"
        android:layout_height="wrap_content"
        android:layout_marginTop="124dp"
        android:text="메인으로 돌아가기"
        android:textSize="24sp"
        app:layout_constraintEnd_toEndOf="parent"
        app:layout_constraintHorizontal_bias="0.498"
        app:layout_constraintStart_toStartOf="parent"
        app:layout_constraintTop_toTopOf="parent" />
</androidx.constraintlayout.widget.ConstraintLayout>

 

▼Sub1Activity.java

package com.example.my12_lifecycle;

import androidx.appcompat.app.AppCompatActivity;

import android.app.Activity;
import android.content.SharedPreferences;
import android.nfc.Tag;
import android.os.Bundle;
import android.util.Log;
import android.view.View;
import android.widget.Button;

public class Sub1Activity extends AppCompatActivity {
    //로그캣 설정
    private static final String TAG = "Sub1Activity";

    @Override
    protected void onCreate(Bundle savedInstanceState) {
        super.onCreate(savedInstanceState);
        setContentView(R.layout.activity_sub1);

        Button btnSub = findViewById(R.id.btnSub);

        //누르면 창이 닫히게끔 설정
        btnSub.setOnClickListener(new View.OnClickListener() {
            @Override
            public void onClick(View v) {
                finish();
            }
        });
    }
}