package org.elvalad.filepersistencetest;

import android.app.Activity;

import android.content.Context;

import android.os.Bundle;

import android.text.TextUtils;

import android.view.Menu;

import android.view.MenuItem;

import android.widget.EditText;

import android.widget.Toast;

import java.io.BufferedReader;

import java.io.BufferedWriter;

import java.io.FileInputStream;

import java.io.FileOutputStream;

import java.io.IOException;

import java.io.InputStreamReader;

import java.io.OutputStreamWriter;

public class MainActivity extends Activity {

    private EditText edit;

    @Override

    protected void onCreate(Bundle savedInstanceState) {

        super.onCreate(savedInstanceState);

        setContentView(R.layout.activity_main);

        edit = (EditText) findViewById(R.id.edit);

        String inputText = load();

        if (!TextUtils.isEmpty(inputText)) {

            edit.setText(inputText);

            edit.setSelection(inputText.length());

            Toast.makeText(MainActivity.this, "Restoring successed", Toast.LENGTH_SHORT).show();

        }

    }

    @Override

    protected void onDestroy() {

        super.onDestroy();

        String inputText = edit.getText().toString();

        save(inputText);

    }

    public void save(String inputText) {

        FileOutputStream out = null;

        BufferedWriter writer = null;

        try {

            out = openFileOutput("data", Context.MODE_APPEND);

            writer = new BufferedWriter(new OutputStreamWriter(out));

            writer.write(inputText);

        } catch (IOException e) {

            e.printStackTrace();

        } finally {

            try {

                if (writer != null) {

                    writer.close();

                }

            } catch (IOException e) {

                e.printStackTrace();

            }

        }

    }

    public String load() {

        FileInputStream in = null;

        BufferedReader reader = null;

        StringBuilder content = new StringBuilder();

        try {

            in = openFileInput("data");

            reader = new BufferedReader(new InputStreamReader(in));

            String line = "";

            while ((line = reader.readLine()) != null) {

                content.append(line);

            }

        } catch (IOException e) {

            e.printStackTrace();

        } finally {

            if (reader != null) {

                try {

                    reader.close();

                } catch (IOException e) {

                    e.printStackTrace();

                }

            }

        }

        return content.toString();

    }

    @Override

    public boolean onCreateOptionsMenu(Menu menu) {

        // Inflate the menu; this adds items to the action bar if it is present.

        getMenuInflater().inflate(R.menu.menu_main, menu);

        return true;

    }

    @Override

    public boolean onOptionsItemSelected(MenuItem item) {

        // Handle action bar item clicks here. The action bar will

        // automatically handle clicks on the Home/Up button, so long

        // as you specify a parent activity in AndroidManifest.xml.

        int id = item.getItemId();

        //noinspection SimplifiableIfStatement

        if (id == R.id.action_settings) {

            return true;

        }

        return super.onOptionsItemSelected(item);

    }

}

<LinearLayout xmlns:android="http://schemas.android.com/apk/res/android"

    xmlns:tools="http://schemas.android.com/tools"

    android:layout_width="match_parent"

    android:layout_height="match_parent"

    android:paddingLeft="@dimen/activity_horizontal_margin"

    android:paddingRight="@dimen/activity_horizontal_margin"

    android:paddingTop="@dimen/activity_vertical_margin"

    android:paddingBottom="@dimen/activity_vertical_margin"

    android:orientation="horizontal"

    tools:context=".MainActivity">

    <EditText

        android:id="@+id/edit"

        android:layout_width="match_parent"

        android:layout_height="wrap_content"

        android:hint="Type something here"/>

</LinearLayout>