External Storage in Android

Introduction

This article explains External Storage in Android.

Android provides many options to store application data. The choice depends on your needs, such as whether the data should be accessible from other applications and how much space your data needs.

We can also store data to and read data from the external storage just like internal storage. The "FileInputStream" and "FileOutPutStream" classes are used to save and read data into the files.

External Storage

Every Android device provides storage space to save files known as external storage. Data from the external storage can be removed and can be modifiable by the user.

Internal storage

Store private data on the device memory. You can directly save your application data to the internal memory. By default data is saved in internal memory and other applications cannot access it. When you uninstall your application all files will be removed from the device.

The FileInoutStream and FileOutPutStream classes are used to read and write data into the files.

FileInputStream

The FileInputStream gets input bytes from a file. The FileInputStream class provides the facility to read streams of raw bytes such as image data. It extends the InputStream class. The following are methods provided by the fileInputStream class:

public int read()
reads a single byte from this Stream and returns it as an integer in the range from 0 to 225.
public void close()
closes the stream.

FileOutPutStream

FileOutputStraem is an output stream for writing data to a file. It extends the OutputStream class. The following are methods provided by the outputStream class:

public void close()
closes the stream.
public void write()
writes a single byte to the stream.

Step 1

Step 2

Create an XML file with this:

<RelativeLayout 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"
tools:context=".MainActivity" >
<LinearLayout
android:id="@+id/linearlayout1"
android:layout_height="wrap_content"
android:orientation="horizontal"
android:layout_width="fill_parent">
<TextView
android:id="@+id/textView1"
android:layout_width="wrap_content"
android:layout_height="wrap_content"
android:text="File Name:" />
<EditText
android:id="@+id/edtText1"
android:layout_width="wrap_content"
android:layout_height="wrap_content"
android:layout_marginLeft="20dp"
android:ems="10" >
</EditText>
</LinearLayout>
<LinearLayout
android:layout_below="@+id/linearlayout1"
android:layout_height="wrap_content"
android:orientation="horizontal"
android:layout_width="fill_parent">
<TextView
android:id="@+id/textView2"
android:layout_width="wrap_content"
android:layout_height="wrap_content"
android:text="Data:" />
<EditText
android:id="@+id/edtText2"
android:layout_width="wrap_content"
android:layout_height="wrap_content"
android:layout_marginLeft="50dp"
android:ems="10" />
</LinearLayout>
<Button
android:id="@+id/save_btn"
android:layout_width="wrap_content"
android:layout_height="wrap_content"
android:layout_marginLeft="170dp"
android:layout_marginTop="150dp"
android:text="save" />
<Button
android:id="@+id/read_btn"
android:layout_marginLeft="50dp"
android:layout_marginTop="150dp"
android:layout_width="wrap_content"
android:layout_height="wrap_content"
android:text="read" />
</RelativeLayout>

Step 3

Create a Java class file with this:

package com.compsapp;
import java.io.BufferedReader;
import java.io.File;
import java.io.FileInputStream;
import java.io.FileNotFoundException;
import java.io.FileOutputStream;
import java.io.IOException;
import java.io.InputStreamReader;
import java.io.OutputStreamWriter;
import android.os.Bundle;
import android.app.Activity;
import android.content.Context;
import android.view.Menu;
import android.view.View;
import android.view.View.OnClickListener;
import android.widget.Button;
import android.widget.EditText;
import android.widget.Toast;
public class MainActivity extends Activity {
EditText edt_FileName,edt_Data;
Button save_btn,read_btn;
@Override
protected void onCreate(Bundle savedInstanceState) {
super.onCreate(savedInstanceState);
setContentView(R.layout.activity_main);
edt_FileName=(EditText)findViewById(R.id.edtText1);
edt_Data=(EditText)findViewById(R.id.edtText2);
save_btn=(Button)findViewById(R.id.save_btn);
read_btn=(Button)findViewById(R.id.read_btn);
//Performing action on save button
save_btn.setOnClickListener(new OnClickListener(){
@Override
public void onClick(View arg0) {
String filename=edt_FileName.getText().toString();
String data=edt_Data.getText().toString();
FileOutputStream fos;
try {
File my_file = new File("/sdcard/"+filename);
my_file.createNewFile();
FileOutputStream fileOutputStream = new FileOutputStream(my_file);
OutputStreamWriter OutWriter = new OutputStreamWriter(fileOutputStream);
OutWriter.append(data);
OutWriter.close();
fileOutputStream.close();
Toast.makeText(getApplicationContext(),filename + " saved",Toast.LENGTH_LONG).show();
} catch (FileNotFoundException e) {e.printStackTrace();}
catch (IOException e) {e.printStackTrace();}
}
});
//Performing action on Read Button
read_btn.setOnClickListener(new OnClickListener(){
@Override
public void onClick(View arg0) {
String filename=edt_FileName.getText().toString();
StringBuffer Buffer = new StringBuffer();
String DataRow = "";
String aBuffer = "";
try {
File myfile = new File("/sdcard/"+filename);
FileInputStream fIn = new FileInputStream(myfile);
BufferedReader bufferedReader = new BufferedReader(
new InputStreamReader(fIn));
while ((DataRow = bufferedReader.readLine()) != null) {
aBuffer += DataRow + "\n";
}
bufferedReader.close();
} catch (IOException e) {
e.printStackTrace();
}
Toast.makeText(getApplicationContext(),aBuffer,Toast.LENGTH_LONG).show();
}
});
}
@Override
public boolean onCreateOptionsMenu(Menu menu) {
// Inflate the menu; this adds items to the action bar if it is present.
getMenuInflater().inflate(R.menu.main, menu);
return true;
}
}

Step 4

In the Android Manifest. xml file give the external storage permission as in the following:

<?xml version="1.0" encoding="utf-8"?>
<manifest xmlns:android="http://schemas.android.com/apk/res/android"
package="com.compsapp"
android:versionCode="1"
android:versionName="1.0" >
<uses-sdk
android:minSdkVersion="8"
android:targetSdkVersion="18" />
<application
android:allowBackup="true"
android:icon="@drawable/ic_launcher"
android:label="@string/app_name"
android:theme="@style/AppTheme" >
<activity
android:name="com.compsapp.MainActivity"
android:label="@string/app_name" >
<intent-filter>
<action android:name="android.intent.action.MAIN" />
<category android:name="android.intent.category.LAUNCHER" />
</intent-filter>
</activity>
</application>
<uses-permission android:name="android.permission.WRITE_EXTERNAL_STORAGE"/>
</manifest>

Step 5