[Android] 파일 처리의 기본

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:orientation="vertical"
    tools:context=".MainActivity">
    <Button
        android:id="@+id/btnWrite"
        android:layout_width="match_parent"
        android:layout_height="wrap_content"
        android:backgroundTint="#50000000"
        android:textColor="@color/black"
        android:text="내장 메모리에 파일 쓰기"/>
    <Button
        android:id="@+id/btnRead"
        android:layout_width="match_parent"
        android:layout_height="wrap_content"
        android:backgroundTint="#50000000"
        android:textColor="@color/black"
        android:text="내장 메모리에서 파일 읽기"/>

</LinearLayout>

MainActivity.java

package com.example.file;

import androidx.appcompat.app.AppCompatActivity;

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

import java.io.FileInputStream;
import java.io.FileOutputStream;
import java.io.IOException;
import java.nio.charset.StandardCharsets;

public class MainActivity extends AppCompatActivity {

    @Override
    protected void onCreate(Bundle savedInstanceState) {
        super.onCreate(savedInstanceState);
        setContentView(R.layout.activity_main);
        Button btnRead, btnWrite;
        btnRead = (Button) findViewById(R.id.btnRead);
        btnWrite = (Button) findViewById(R.id.btnWrite);

        btnWrite.setOnClickListener(new View.OnClickListener() {
            @Override
            public void onClick(View view) {
                try{
                    FileOutputStream outFs = openFileOutput("file.txt", Context.MODE_PRIVATE);
                    String str = "쿡북 안드로이드";
                    outFs.write(str.getBytes());
                    outFs.close();
                    Toast.makeText(getApplicationContext(),"file.txt가 생성됨", Toast.LENGTH_SHORT).show();
                }catch (IOException e){}
            }
        });

        btnRead.setOnClickListener(new View.OnClickListener() {
            @Override
            public void onClick(View view) {
                try {
                    FileInputStream inFs = openFileInput("file.txt");
                    byte[] txt = new byte[30];
                    inFs.read(txt);
                    String str = new String(txt);
                    Toast.makeText(getApplicationContext(),str,Toast.LENGTH_SHORT).show();
                    inFs.close();
                }catch (IOException e){
                    Toast.makeText(getApplicationContext(),"파일 없음",Toast.LENGTH_SHORT);
                }
            }
        });
    }
}

 

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