File read/write using the android sub-function

File read/write using the android sub-function
Create an Android project.


1 Layout
First look:

Open main. xml and modify the content as follows:

Binary definition string
Open strings. xml and add the following content:

     
  
   
File
      
  
   
Settings
      
  
   
File Name
      
  
   
File Content
      
  
   
Save
      
  
   
Saved
      
  
   
Failed to save
      
  
   
Read
      
  
   
Read successful
      
  
   
Reading failed
  
 

Three Functions
Create a new FileService class for reading and writing files. The complete code is as follows:

Public class FileService {public Context context; public FileService (Context context) {this. context = context;}/*** save the String to the file * @ param name file name * @ param content File content */public void save (String name, String content) throws Exception {// The File Created by MODE_PRIVATE can only be accessed by this application, and the newly written content will overwrite the original content FileOutputStream OS = context. openFileOutput (name, Context. MODE_PRIVATE); // It is stored in/data/by default/
 
  
/Files directory OS. write (content. getBytes (); OS. close ();}/***** read File Content * @ param name file name * @ return * @ throws Exception */public String read (String name) throws Exception {FileInputStream is = context. openFileInput (name); ByteArrayOutputStream OS = new ByteArrayOutputStream (); byte [] buf = new byte [1024]; int len = 0; while (len = is. read (buf ))! =-1) {OS. write (buf, 0, len);} byte [] data = OS. toByteArray (); String content = new String (data); return content ;}}
 

4. Test code
The code for modifying MainActivity. java is as follows:

    public EditText nameText;    public EditText saveContentText;    public EditText readContentText;    public Button button_read;    public String filename;    @Override    protected void onCreate(Bundle savedInstanceState) {        super.onCreate(savedInstanceState);        setContentView(R.layout.activity_main);        nameText = (EditText)this.findViewById(R.id.filename);        saveContentText = (EditText)this.findViewById(R.id.save_file_content);        readContentText = (EditText)this.findViewById(R.id.read_file_content);        Button button_save = (Button) this.findViewById(R.id.button_save);        button_save.setOnClickListener(new ButtonSaveClickListener());        button_read = (Button) this.findViewById(R.id.button_read);        button_read.setClickable(false);        button_read.setOnClickListener(new ButtonReadClickListener());    }    private final class ButtonSaveClickListener implements View.OnClickListener{        public void onClick(View v){            String name = nameText.getText().toString();            String content = saveContentText.getText().toString();            FileService service = new FileService(getApplicationContext());            try {                filename = name;                service.save(name, content);                filename = name;                button_read.setClickable(true);                Toast.makeText(getApplicationContext(),R.string.save_success, Toast.LENGTH_LONG).show();            }catch (Exception e){                Toast.makeText(getApplicationContext(),R.string.save_fail, Toast.LENGTH_LONG).show();                e.printStackTrace();            }        }    }    private final class ButtonReadClickListener implements View.OnClickListener{        public void onClick(View v){            FileService service = new FileService(getApplicationContext());            try {                String content = service.read(filename);                readContentText.setText(content);                Toast.makeText(getApplicationContext(),R.string.read_success, Toast.LENGTH_LONG).show();            }catch (Exception e){                Toast.makeText(getApplicationContext(),R.string.read_fail, Toast.LENGTH_LONG).show();                e.printStackTrace();            }        }    }

Running result