Android_Java(15) - FileExternalApp

외부 저장(External Storage)
        - 착탈이 가능한 SD 카드 
        - 외부 저장 공간에 저장된 파일들은 누구나 읽을 수 있으며, 사용자가 변경 가능 

<?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="fill_parent"
    android:layout_height="fill_parent"
    android:id="@+id/linearLayout01"
    android:orientation="vertical"
    tools:context=".MainActivity">

   <LinearLayout
       android:layout_width="fill_parent"
       android:layout_height="fill_parent"
       android:layout_weight="1"
       android:id="@+id/linearLayout02">

       <EditText
           android:layout_width="fill_parent"
           android:layout_height="fill_parent"
           android:id="@+id/editText"/>
   </LinearLayout>

    <LinearLayout
        android:layout_width="wrap_content"
        android:layout_height="wrap_content"
        android:id="@+id/linearLayout03">

        <Button
            android:layout_width="wrap_content"
            android:layout_height="wrap_content"
            android:id="@+id/read"
            android:text="읽기"/>
        <Button
            android:layout_width="wrap_content"
            android:layout_height="wrap_content"
            android:id="@+id/write"
            android:text="쓰기"/>
    </LinearLayout>

</LinearLayout>

외부 저장(External Storage)
        - 착탈이 가능한 SD 카드 
        - 외부 저장 공간에 저장된 파일들은 누구나 읽을 수 있으며, 사용자가 변경 가능 

package kr.co.fileexternalapp;

import androidx.appcompat.app.AppCompatActivity;

import android.os.Bundle;
import android.os.Environment;
import android.view.View;
import android.widget.Button;
import android.widget.EditText;
import android.widget.Toast;

import java.io.File;
import java.io.FileInputStream;
import java.io.FileOutputStream;
import java.io.InputStream;
import java.io.OutputStream;

public class MainActivity extends AppCompatActivity {

    String FILENAME = "externalfile.txt";
    EditText editText;

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

        //외부 미디어 장착 여부 체크
        String state = Environment.getExternalStorageState();
        if(state.equals(Environment.MEDIA_MOUNTED) == false){
            Toast.makeText(this, "외부 스토리지 마운트 실패", Toast.LENGTH_SHORT).show();
        }
        editText = findViewById(R.id.editText);
        Button readButton = findViewById(R.id.read);
        readButton.setOnClickListener(new View.OnClickListener() {
            @Override
            public void onClick(View view) {
                File file = new File(getExternalFilesDir(null), FILENAME);
                try {
                    InputStream is = new FileInputStream(file);
                    byte[] buffer = new byte[is.available()];

                    is.read(buffer);
                    editText.setText(new String(buffer));
                    is.close();

                    Toast.makeText(getApplicationContext(), "외부 스토리지 읽기 성공", Toast.LENGTH_SHORT).show();
                }catch (Exception e ){
                    e.printStackTrace();
                }
            }
        });

        Button writeButton = findViewById(R.id.write);
        writeButton.setOnClickListener(new View.OnClickListener() {
            @Override
            public void onClick(View view) {
                File file = new File(getExternalFilesDir(null), FILENAME);
                try {
                    OutputStream os = new FileOutputStream(file);
                    os.write(editText.getText().toString().getBytes());
                    os.close();

                    Toast.makeText(getApplicationContext(), "외부 스토리지 쓰기 성공", Toast.LENGTH_SHORT).show();
                } catch (Exception e){
                    e.printStackTrace();
                }
            }
        });
    }
}

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[결과 출력]

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