AS初級［メモ帳］ファイル入出力編①解説

MainActivity.java

package com.example.frg;

import androidx.appcompat.app.AppCompatActivity;

import android.content.Context;
import android.os.Bundle;
import android.view.Menu;
import android.view.MenuInflater;
import android.view.MenuItem;
import android.widget.EditText;
import android.widget.TextView;

import java.io.BufferedReader;
import java.io.BufferedWriter;
import java.io.FileInputStream;
import java.io.FileNotFoundException;
import java.io.FileOutputStream;
import java.io.IOException;
import java.io.InputStreamReader;
import java.io.OutputStreamWriter;

public class MainActivity extends AppCompatActivity {

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

        editText = findViewById(R.id.editText);
        showText = findViewById(R.id.showText);
    }

    @Override
    public boolean onCreateOptionsMenu(Menu menu) {
        MenuInflater inflater = getMenuInflater();
        inflater.inflate(R.menu.memochou_menu, menu);
        return true;
    }

    public boolean onOptionsItemSelected(MenuItem item){
        switch (item.getItemId()) {
            case R.id.save:
                save();
                return true;
            case R.id.read:
                read();
                return true;
            default:
                return super.onOptionsItemSelected(item);
        }
    }

    public void save(){
        try{
            FileOutputStream fileOutputStream = openFileOutput("Sample.txt", Context.MODE_PRIVATE);

            BufferedWriter saveText = new BufferedWriter(new OutputStreamWriter(fileOutputStream));

            saveText.write(editText.getText().toString());

            saveText.flush();

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

    public void read(){
        try {
            FileInputStream fileInputStream = openFileInput("Sample.txt");
            BufferedReader bufferedReader = new BufferedReader(new InputStreamReader(fileInputStream));
            StringBuilder sequence = new StringBuilder();
            String readText;
            while ((readText = bufferedReader.readLine())!=null){
                sequence.append(readText);
            }
            showText.setText(sequence.toString());
            fileInputStream.close();
        } catch (FileNotFoundException e) {
            e.printStackTrace();
        } catch (IOException e) {
            e.printStackTrace();
        }


    }
}

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"
    tools:context=".MainActivity"
    android:gravity="center_horizontal"
    android:orientation="vertical">

    <TextView
        android:layout_width="wrap_content"
        android:layout_height="wrap_content"
        android:text="入力したいテキストを下に入力してください。"/>

    <EditText
        android:id="@+id/editText"
        android:layout_width="match_parent"
        android:layout_height="wrap_content"
        android:layout_marginTop="40sp"/>

    <TextView
        android:id="@+id/showText"
        android:layout_width="match_parent"
        android:layout_height="match_parent"/>


</LinearLayout>

memochou_menu.xml（res下にmenuディレクトリを作成し、そこに作成）

<?xml version="1.0" encoding="utf-8"?>
<menu xmlns:app="http://schemas.android.com/apk/res-auto"
    xmlns:android="http://schemas.android.com/apk/res/android">

    <item android:id="@+id/save"
        android:title="@string/save" />
    <item android:id="@+id/read"
        android:title="@string/read" />
</menu>

string.xml も変更します。

<resources>
    <string name="app_name">Frg</string>
    <string name="read">読み込み</string>
    <string name="save">保存</string>
</resources>

保存場所は、調べたのですが不明です。

下記を参照にしてます。

https://developer.android.com/guide/topics/ui/menus?hl=ja