<?xml version="1.0" encoding="utf-8"?>

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

     android:id="@+id/activity_main"

     android:layout_width="match_parent"

     android:layout_height="match_parent">

     <EditText

         android:id="@+id/edit"

         android:layout_width="match_parent"

         android:layout_height="wrap_content"

         android:hint="Type something here"/>

 </LinearLayout>

 public class MainActivity extends AppCompatActivity {

     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)){                                 //对字符串进行非空判断

             edit.setText(inputText);

             edit.setSelection(inputText.length());

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

         }

     }

     @Override

     protected void onDestroy(){                                           //重写onDestroy()保证在活动销毁之前一定调用这个方法

         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_PRIVATE);

             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();

     }

 }