文件存储

<?xml version="1.0" encoding="utf-8"?>
<android.support.constraint.ConstraintLayout 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="com.example.filepersistencetest.MainActivity">

   <EditText
       android:id="@+id/edit"
       android:layout_width="match_parent"
       android:layout_height="wrap_content"
       android:hint="输入一些东西看看"
       />

</android.support.constraint.ConstraintLayout>

package com.example.filepersistencetest;

import android.content.Context;
import android.support.v7.app.AppCompatActivity;
import android.os.Bundle;
import android.text.TextUtils;
import android.util.Log;
import android.widget.EditText;
import android.widget.Toast;

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 {

    private static final String TAG = "MainActivity";
    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(this,"还原(保存)成功",Toast.LENGTH_LONG).show();

        }


    }

    @Override
    protected void onDestroy() {
        super.onDestroy();
        String inputText = edit.getText().toString();

        Log.d(TAG, "输入的文字为: "+inputText);

        save(inputText);
    }

    private void save(String inputText) {
        FileOutputStream out = null;
        BufferedWriter writer = null;

        try {
            out =  openFileOutput("data", Context.MODE_PRIVATE);
            writer = new BufferedWriter(new OutputStreamWriter(out));
            writer.write(inputText);
        } catch (Exception e) {
            e.printStackTrace();
        } finally {
            try{
                if(writer!=null){
                    writer.close();
                }
            }catch (Exception 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(Exception e){
            e.printStackTrace();
        }

        Log.d(TAG, "读取到的文件的内容为: "+content.toString());
        return content.toString();
    }

}