How to read and write files in you Android Application

When coding an application for the Android system, you will eventually need to store some data on the phones for later use. There are generally two ways of doing this – either in files or by using a SQLlite database.

Write to file

So your sitting there with your fancy newly developed application, but all your settings are going back to default values when the program starts. Why not just write the settings to a file and then read the file content when the application starts up.

To do this we need the OutputStream and OutputStreamReader, so lets import them like this:

import java.io.OutputStream;
import java.io.OutputStreamWriter;

Lets say the application has a save button somewhere and when this is clicked the onClick(View) is called. We can then add some code, to handle the file writing:

...
public void onClick(View view) {
...
// try to write the content
try {
  // open myfilename.txt for writing
  OutputStreamWriter out = new OutputStreamWriter(openFileOutput("myfilename.txt",0));
  // write the contents on mySettings to the file
  out.write(mySettings);
  // close the file
  out.close();
} catch (java.io.IOException e) {
  //do something if an IOException occurs.
}

There you go. The content from the mySettings variable should now be writting to the file myfilename.txt. How the settings come from the application to the mySettings variable is another subject and is not covered here.

Reading lines from a file

Now we have some data information writting to the myfilename.txt-file, that now exits on the Android device.

To read the information from the file, we need to the InputReader, InputReaderStream and BufferedReader, so just import them like this:

import java.io.InputStream;
import java.io.InputStreamReader;
import java.io.BufferedReader;

All we have to do now, is open the myfilename.txt for reading. This could be done like this:

...
  // try opening the myfilename.txt
  try {
    // open the file for reading
    InputStream instream = openFileInput("myfilename.txt");

    // if file the available for reading
    if (instream) {
      // prepare the file for reading
      InputStreamReader inputreader = new InputStreamReader(instream);
      BufferedReader buffreader = new BufferedReader(inputreader);
                
      String line;

      // read every line of the file into the line-variable, on line at the time
      while (( line = buffreader.readLine())) {
        // do something with the settings from the file
      }

    }
    
    // close the file again       
    instream.close();
  } catch (java.io.FileNotFoundException e) {
    // do something if the myfilename.txt does not exits
  }
...

We have now read the content of the myfilename.txt and made it available for the application.

To read more about this Android check out these books: here

16 Responses to “Android writing and reading files”

Website Designer Says:
september 29th, 2010 at 12:36
Hi,

How to read and write files in you Android Application When coding an application for the Android system.

Thanks,
Allec
alma Says:
oktober 24th, 2010 at 22:54
InputStream in

not acceptable in IF condition

and typo in variable name: input ~ inputreader

did u run this code ever?
weidberg Says:
oktober 28th, 2010 at 10:52
thank you very much for the great code,
it works wonderful.
after I write to the file “myfilename.txt”, where could i find it, when i’m running the android emulator?

thenks
js - huuah Says:
oktober 30th, 2010 at 13:19
#2 alma
I have corrected the typo – thank you.

Yes – I have tested the code, but it was part of some other tests, so I re-type the example code on my blog. To be honest I can not remember if I compiled and ran the code. That’s my mistake – sorry.
Sambit Aryal Says:
december 31st, 2010 at 08:44
hello,
how settings from application comes to mysettings? any help will be appreciated.
sneha Says:
januar 4th, 2011 at 07:11
where should I copied for read myfilename.txt in my application
aftab Says:
februar 5th, 2011 at 09:29
hi all is fine . but where can i find these files stored in android internal storage ? same how can I explore DB saved in android ?
rosy Says:
marts 23rd, 2011 at 07:22
where could i find myfilename.txt, when i’m running the android emulator?
Ripu Daman Says:
maj 13th, 2011 at 08:15
When I read the value from the file how do i set it on the spinner(combobox)??
so that whenever i open my app it shows the last selected value on the spinner & not the default value(the first value in the spinner)?

Plzz help..It would be highly appreciated.!
Gyubok Baik Says:
juni 16th, 2011 at 12:29
Thank for the code! I greatly appreciate it.

I have two questions. How would I transfer text from buffreader to a string?

Also, it seems like “if (instream)” seems incomplete. What goes inside “if (…)”?
Gyubok Baik Says:
juni 16th, 2011 at 14:02
If I save the file, is it saved inside SD card? If not, how can I make it save inside SD card?
Aditya Says:
juli 28th, 2011 at 07:43
Its running without any error but content are not written in txt file.
Any help….

Thanks,
Aditya
Muhammad Mubashir Says:
august 4th, 2011 at 09:16
package com.example;

import java.io.ByteArrayOutputStream;
import java.io.FileNotFoundException;
import java.io.IOException;
import java.io.InputStream;
import java.net.HttpURLConnection;
import java.net.MalformedURLException;
import java.net.ProtocolException;
import java.net.URL;
import android.app.Activity;
import android.content.res.AssetManager;
import android.content.res.Resources;
import android.os.Bundle;
import android.util.Log;
import android.widget.TextView;

public class GetFromURLActivity extends Activity
{
TextView txtContent;
String path;

/** Called when the activity is first created. */
@Override
public void onCreate(Bundle savedInstanceState)
{
super.onCreate(savedInstanceState);
setContentView(R.layout.main);

try {
//this is the file you want to download from the remote server

/*path =”http://localhost:82/TextureTest01.apk”;*/
path =”http://10.0.2.2:82/my.txt”;
//this is the name of the local file you will create

/*String targetFileName = “mynew”; // Omit extension.
boolean eof = false;*/
URL u = new URL(path);

HttpURLConnection c = (HttpURLConnection) u.openConnection();

c.setRequestMethod(“GET”);
c.setDoOutput(true);
c.connect();

InputStream in = c.getInputStream();

Log.e(“value”,in.toString());

//Gets the instance of the asset manager
AssetManager mngr=getAssets();

//Resources resources = new Resources();
//resources.getAssets().open(“my.txt”);
//FileOutputStream f = new FileOutputStream(new File(“c:\\” + targetFileName));

/*FileOutputStream f = this.openFileOutput(targetFileName,
this.MODE_WORLD_READABLE);*/

ByteArrayOutputStream bo = new ByteArrayOutputStream();

byte[] buffer = new byte[1024];
in.read(buffer); // Read from Buffer.
bo.write(buffer); // Write Into Buffer.

/*int len1 = 0;
while ( (len1 = in.read(buffer)) != -1 )
{
//f.write(buffer,0, len1);
bo.write(buffer,0, len1); // Write Into Buffer.
}*/
txtContent =(TextView)findViewById(R.id.textview);
txtContent.setText(bo.toString());
bo.close();
//f.close();

}
catch (MalformedURLException e) {
e.printStackTrace();
//txtContent.setText(e.getMessage().toString());
} catch (ProtocolException e) {
e.printStackTrace();
//txtContent.setText(e.getMessage().toString());
} catch (FileNotFoundException e) {
e.printStackTrace();
//txtContent.setText(e.getMessage().toString());
} catch (IOException e) {
e.printStackTrace();
//txtContent.setText(e.getMessage().toString());
}
}
String ReadFile(InputStream is)
{
ByteArrayOutputStream bo=new ByteArrayOutputStream();

byte [] buffer=new byte[1024];

try {
is.read(buffer);
bo.write(buffer);

bo.close();
is.close();
} catch (IOException e) {
// TODO Auto-generated catch block
e.printStackTrace();
}
return bo.toString();
}
}

// my Email id is muhammad.mubashir.bscs@gmail.com
Kasper Says:
august 19th, 2011 at 13:01
Not saying writing settings to a file is wrong, but it’s really not the way Android does it.

For persisting settings between app close and startups you should really use the “SharedPreferences” interface and override the onPause method of the activity:

@override
protected void onPause() {

SharedPreferences preferences = getPreferences(MODE_PRIVATE);
SharedPreferences.Editor editor = preferences.edit();

editor.putString(“username”, myUserName);
}

and then get the saved vars afterwards in the onCreate method.
Sarwesh Suman Says:
september 3rd, 2011 at 09:05
Hi,
Can any one please tell that is there any library in android sdk which can be used to read write a MS word, excel?
neel Says:
maj 17th, 2012 at 18:08
the correct code for the reading, writing and deleting a file from internal storage from a device

package com.halosys.android.internalstorage;

import java.io.File;
import java.io.FileInputStream;
import java.io.FileNotFoundException;
import java.io.FileOutputStream;
import java.io.IOException;

import android.app.Activity;
import android.content.Context;
import android.os.Bundle;
import android.view.View;
import android.widget.Button;
import android.widget.EditText;
import android.widget.TextView;

public class WriteAFileToInternalStorageActivity extends Activity {

private TextView mWrite;
private TextView mRead;
private Button write;
public EditText et;
private Button read;
private Button delete;
public static int i=1;

/** Called when the activity is first created. */
@Override
public void onCreate(Bundle savedInstanceState) {
super.onCreate(savedInstanceState);
setContentView(R.layout.main);
et=(EditText)findViewById(R.id.editText1);
write = (Button)findViewById(R.id.button1);

write.setOnClickListener(new View.OnClickListener() {
public void onClick(View v) {
String FILENAME = “hello_file.txt”;
String string = “hello world!”;

FileOutputStream fos = null;
try {
fos = openFileOutput(FILENAME, Context.MODE_WORLD_WRITEABLE);

} catch (FileNotFoundException e) {

e.printStackTrace();
}
try {
fos.write(string.getBytes());
} catch (IOException e) {

e.printStackTrace();
}
try {
fos.close();
} catch (IOException e) {

e.printStackTrace();
}
}
});

read = (Button)findViewById(R.id.button2);

/* read.setOnClickListener(new View.OnClickListener() {
public void onClick(View v) {
try {

File myFile = new File(“/hello_file.txt”);
FileInputStream fis = new FileInputStream(myFile);
BufferedReader myReader = new BufferedReader(
new InputStreamReader(fis));
String aDataRow = “”;
String aBuffer = “”;
StringBuffer fileContent = new StringBuffer(“”);
byte[] buffer = new byte[1024];
int length;
while ((length = fis.read(buffer)) != -1) {
fileContent.append(new String(buffer));
}

et.setText(aBuffer);
myReader.close();
Toast.makeText(getBaseContext(),
“Done reading SD ‘hello_file.txt’”,
Toast.LENGTH_SHORT).show();
} catch (Exception e) {
Toast.makeText(getBaseContext(), e.getMessage(),
Toast.LENGTH_LONG).show();
}
}// onClick

});*/

read.setOnClickListener(new View.OnClickListener() {
public void onClick(View v) {
String FILENAME = “hello_file.txt”;
String string = “”;
StringBuffer fileContent = new StringBuffer(“”);

FileInputStream fis = null;
try {
fis = openFileInput(FILENAME);

} catch (FileNotFoundException e) {

e.printStackTrace();
}
try {

byte[] buffer = new byte[1024];
int length=0;
while ((length = fis.read(buffer)) != -1) {
fileContent.append(new String(buffer));
System.out.println(“buffer appended “+i+”time”);
i++;
}
fis.read(buffer);

} catch (IOException e) {

e.printStackTrace();
}
try {
et.setText(fileContent.toString());
System.out.println(fileContent.toString());
fis.close();
} catch (IOException e) {

e.printStackTrace();
}
}
});

delete = (Button)findViewById(R.id.button3);

delete.setOnClickListener(new View.OnClickListener() {
public void onClick(View v) {
String FILENAME = “hello_file.txt”;
String string = “”;
File dir = getFilesDir();
File file = new File(dir, FILENAME);
boolean deleted = file.delete(); }
});

}
}

mail.xml file is like that

How to read and write files in you Android Application

Write to file

Reading lines from a file

16 Responses to “Android writing and reading files”

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