[Android/Java] File stream 외부 Storage에 글 읽고 쓰기

Demo

 

MainActivity.java

package com.example.recyclerview;

import android.os.Bundle;
import android.os.Environment;
import android.speech.tts.TextToSpeech;
import android.view.View;
import android.widget.Button;
import android.widget.EditText;
import android.widget.ImageButton;
import android.widget.TextView;
import android.widget.Toast;

import androidx.appcompat.app.AppCompatActivity;

import java.io.BufferedReader;
import java.io.File;
import java.io.FileNotFoundException;
import java.io.FileOutputStream;
import java.io.FileReader;
import java.io.IOException;
import java.util.Locale;

public class MainActivity extends AppCompatActivity {
    private Button btnSave, btnLoad;
    private EditText etInput;
    private TextView tvLoad;
    private String filename = "";
    private String filepath = "";
    private String fileContent = "";

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

        btnSave = findViewById(R.id.btn_save);
        btnLoad = findViewById(R.id.btn_load);
        etInput = findViewById(R.id.et_input);
        tvLoad = findViewById(R.id.tv_load);
        filename = "myFile.txt";
        filepath = "MyFileDir";
        if(!isExternalStorageAvailableForRW()) {
            btnSave.setEnabled(false);
        }
        btnSave.setOnClickListener(new View.OnClickListener() {
            @Override
            public void onClick(View v) {
                tvLoad.setText("");
                fileContent = etInput.getText().toString().trim();
                if(!fileContent.equals("")) {
                    File myExternalFile = new File(getExternalFilesDir(filepath), filename);
                    FileOutputStream fos = null;
                    try {
                        fos = new FileOutputStream(myExternalFile);
                        fos.write(fileContent.getBytes());
                    } catch (FileNotFoundException e) {
                        e.printStackTrace();
                    } catch (IOException e) {
                        e.printStackTrace();
                    }
                    etInput.setText("");
                    Toast.makeText(MainActivity.this,"Information saved to SD card", Toast.LENGTH_SHORT);
                } else {
                    Toast.makeText(MainActivity.this,"Text field can not be empty", Toast.LENGTH_SHORT);
                }
            }
        });
        btnLoad.setOnClickListener(new View.OnClickListener() {
            @Override
            public void onClick(View v) {
                FileReader fr = null;
                File myExternalFile = new File(getExternalFilesDir(filepath), filename);
                StringBuilder stringBuilder = new StringBuilder();
                try {
                    fr = new FileReader(myExternalFile);
                    BufferedReader br = new BufferedReader(fr);
                    String line = br.readLine();
                    while (line != null) {
                        stringBuilder.append(line).append('\n');
                        line = br.readLine();
                    }
                } catch (FileNotFoundException e) {
                    e.printStackTrace();
                } catch (IOException e) {
                    e.printStackTrace();
                } finally {
                    String fileContents = "File contents\n" + stringBuilder.toString();
                    tvLoad.setText(fileContents);
                }
            }
        });
    }

    private boolean isExternalStorageAvailableForRW() {
        String extStorageState = Environment.getExternalStorageState();
        if(extStorageState.equals(Environment.MEDIA_MOUNTED)){
            return true;
        }
        return false;
    }

}

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"
    android:layout_width="match_parent"
    android:layout_height="match_parent"
    android:orientation="vertical"
    android:gravity="center">

    <EditText
        android:id="@+id/et_input"
        android:layout_width="match_parent"
        android:layout_height="wrap_content"
        android:hint="Type here to save on SD card"/>
    <LinearLayout
        android:layout_width="match_parent"
        android:layout_height="wrap_content"
        android:layout_marginTop="10dp"
        android:orientation="horizontal">
        <Button
            android:id="@+id/btn_save"
            android:layout_width="wrap_content"
            android:layout_height="wrap_content"
            android:layout_marginRight="10dp"
            android:layout_weight="1"
            android:text="Save"/>
        <Button
            android:id="@+id/btn_load"
            android:layout_width="wrap_content"
            android:layout_height="wrap_content"
            android:layout_marginRight="10dp"
            android:layout_weight="1"
            android:text="Load"/>
    </LinearLayout>

    <ScrollView
        android:layout_width="match_parent"
        android:layout_height="80dp">
        <TextView
            android:id="@+id/tv_load"
            android:layout_width="match_parent"
            android:layout_height="wrap_content"
            android:text=""/>
    </ScrollView>
</LinearLayout>

AndroidManifest.xml

<?xml version="1.0" encoding="utf-8"?>
<manifest xmlns:android="http://schemas.android.com/apk/res/android"
    package="com.example.recyclerview">

    <uses-permission android:name="android.permission.WRITE_EXTERNAL_STORAGE"/>
    <uses-permission android:name="android.permission.READ_EXTERNAL_STORAGE"/>

    <application
        android:networkSecurityConfig="@xml/network_security_config"
        android:allowBackup="true"
        android:icon="@mipmap/ic_launcher"
        android:label="@string/app_name"
        android:roundIcon="@mipmap/ic_launcher_round"
        android:supportsRtl="true"
        android:theme="@style/Theme.RecyclerView">
        <!--android:screenOrientation="landscape"
            android:turnScreenOn="true"-->
        <activity android:name=".MainActivity"
            android:theme="@style/Theme.AppCompat.NoActionBar"
            >
            <intent-filter>
                <action android:name="android.intent.action.MAIN" />

                <category android:name="android.intent.category.LAUNCHER" />
            </intent-filter>
        </activity>
    </application>

</manifest>