Android_Java(14) - FileApp

 파일처리 

 1. 데이터를 저장하는 방법
    1) 내부 저장(Internal Storage)
        - 사적인 데이터를 내부 저장소에 저장 
            - 모든 장치에 존재, 항상 사용할 수 있음 
            - 디렉토리가 포함되어 있음 
            - 내부 저장 공간에 저장되는 파일은 해당 앱에서만 접근이 가능함
            - 사용자가 앱을 제거하면 이들 파일들도 제거됨 
            - 내장 메모리 저장 위치 
                - /data/data/패키지명/files 폴더
            - 내장 메모리에서 파일 처리 
                - 파일 열기
                    - FileOutputStream/FileInputStream의 openFileOutput()/openFileInput()
                - 파일 읽기/쓰기
                    - read()/write()
                - 파일 닫기
                    - close() 
            - 파일 이름은  
    2) 외부 저장(External Storage)
    3) SQLite DB 
        - 구조화된 데이터를 사적인 DB에 저장
    4) 네트워크 연결
        - 데이터를 서버에 저장 

---

<activity_main.xml>

<?xml version="1.0" encoding="utf-8"?>
<LinearLayout 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"
    android:gravity="center"
    android:orientation="vertical"
    tools:context=".MainActivity">

    <DatePicker
        android:layout_width="wrap_content"
        android:layout_height="wrap_content"
        android:datePickerMode="spinner"
        android:id="@+id/datePicker"
        android:calendarViewShown="false"/>

    <EditText
        android:layout_width="match_parent"
        android:layout_height="wrap_content"
        android:layout_weight="1"
        android:id="@+id/edtDiary"
        android:background="#00ff00"
        android:lines="8">
    </EditText>

    <Button
        android:layout_width="match_parent"
        android:layout_height="wrap_content"
        android:id="@+id/btnWrite"
        android:text="Diary Write"/>

</LinearLayout>

<MainActivity.java>

package kr.co.fileapp;
/*
    파일 이름 : 연_월_일.txt로 저장
 */
import androidx.appcompat.app.AppCompatActivity;

import android.content.Context;
import android.os.Bundle;
import android.view.View;
import android.widget.Button;
import android.widget.DatePicker;
import android.widget.EditText;
import android.widget.Toast;

import java.io.FileInputStream;
import java.io.FileNotFoundException;
import java.io.FileOutputStream;
import java.io.IOException;
import java.util.Calendar;

public class MainActivity extends AppCompatActivity {

    DatePicker datePicker;
    EditText editText;
    Button btnWrite;
    String fileName;

    @Override
    protected void onCreate(Bundle savedInstanceState) {
        super.onCreate(savedInstanceState);
        setContentView(R.layout.activity_main);
        getSupportActionBar().setDisplayShowHomeEnabled(true);
        getSupportActionBar().setIcon(R.drawable.ic_launcher);
        setTitle("간단한 일기장(수정)");

        datePicker = findViewById(R.id.datePicker);
        editText = findViewById(R.id.edtDiary);
        btnWrite = findViewById(R.id.btnWrite);

        //Calendar 클래스를 이용해 현자 날짜의 연/월/일 구한 후 데이트피커 초기화
        Calendar calendar = Calendar.getInstance();
        int cYear = calendar.get(Calendar.YEAR);
        int cMonth = calendar.get(Calendar.MONTH);
        int cDay = calendar.get(Calendar.DAY_OF_MONTH);

        //파일 이름 : 연_월_일.txt 로 저장
        fileName = Integer.toString(cYear) + "_" + Integer.toString((cMonth + 1))+"_"+Integer.toString(cDay)+".txt";
        String str = readDiary(fileName);
        editText.setText(str);

        //데이터피커의 날짜가 변경되면 변경된 날짜에 해당하는 일기 파일(연_월_일.txt)의 내용을 에디트 텍스트에 보여줌
        datePicker.init(cYear, cMonth, cDay, new DatePicker.OnDateChangedListener() {
            @Override
            public void onDateChanged(DatePicker datePicker, int i, int i1, int i2) {
                fileName = Integer.toString(i) + "_"+ Integer.toString(i1) +"_"+ Integer.toString(i2)+".txt";
                String str = readDiary(fileName);
                editText.setText(str);
            }
        });

        btnWrite.setOnClickListener(new View.OnClickListener() {
            @Override
            public void onClick(View view) {
                try {
                    FileOutputStream outFs = openFileOutput(fileName, Context.MODE_PRIVATE);
                    String str = editText.getText().toString();

                    outFs.write(str.getBytes());
                    outFs.close();

                    Toast.makeText(getApplicationContext(), fileName+ "이 저장됨!", Toast.LENGTH_SHORT).show();

                } catch (IOException e) {
                    e.printStackTrace();
                }
            }
        });
    }

    private String readDiary(String fileName) {
        String diaryStr = null;
        FileInputStream inFs;

        try {
            inFs = openFileInput(fileName);
            byte[] bytes = new byte[500];
            inFs.read(bytes);
            inFs.close();

            diaryStr = (new String(bytes)).trim();
            btnWrite.setText("DIARY EDIT");

        } catch (IOException e ) {
            editText.setHint("읽기 없음");
            e.printStackTrace();
        }

        return diaryStr;
    }
}

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