Android Tutorial - Javatpoint

Basics of Android

Android External Storage Example

Like internal storage, we are able to save or read data from the device external memory such as sdcard. FileInputStream and FileOutputStream classes are used to read and write data into the file.

Example of reading and writing data to the android external storage

activity_main.xml

Drag the 2 edittexts, 2 textviews and 2 buttons from the pallete, now the activity_main.xml file will like this:

File: activity_main.xml

<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" >

    <EditText
        android:id="@+id/editText1"
        android:layout_width="wrap_content"
        android:layout_height="wrap_content"
        android:layout_alignParentRight="true"
        android:layout_alignParentTop="true"
        android:layout_marginRight="20dp"
        android:layout_marginTop="24dp"
        android:ems="10" >

        <requestFocus />
    </EditText>

    <EditText
        android:id="@+id/editText2"
        android:layout_width="wrap_content"
        android:layout_height="wrap_content"
        android:layout_alignRight="@+id/editText1"
        android:layout_below="@+id/editText1"
        android:layout_marginTop="24dp"
        android:ems="10" />

    <TextView
        android:id="@+id/textView1"
        android:layout_width="wrap_content"
        android:layout_height="wrap_content"
        android:layout_alignBaseline="@+id/editText1"
        android:layout_alignBottom="@+id/editText1"
        android:layout_alignParentLeft="true"
        android:text="File Name:" />

    <TextView
        android:id="@+id/textView2"
        android:layout_width="wrap_content"
        android:layout_height="wrap_content"
        android:layout_alignBaseline="@+id/editText2"
        android:layout_alignBottom="@+id/editText2"
        android:layout_alignParentLeft="true"
        android:text="Data:" />

    <Button
        android:id="@+id/button1"
        android:layout_width="wrap_content"
        android:layout_height="wrap_content"
        android:layout_alignLeft="@+id/editText2"
        android:layout_below="@+id/editText2"
        android:layout_marginLeft="70dp"
        android:layout_marginTop="16dp"
        android:text="save" />

    <Button
        android:id="@+id/button2"
        android:layout_width="wrap_content"
        android:layout_height="wrap_content"
        android:layout_alignBaseline="@+id/button1"
        android:layout_alignBottom="@+id/button1"
        android:layout_toRightOf="@+id/button1"
        android:text="read" />

</RelativeLayout>

Provide permission for the external storage

You need to provide the WRITE_EXTERNAL_STORAGE permission.

<uses-permission android:name="android.permission.WRITE_EXTERNAL_STORAGE"/>

File: Activity_Manifest.xml

<?xml version="1.0" encoding="utf-8"?>
<manifest xmlns:android="http://schemas.android.com/apk/res/android"
    package="com.example.externalstorage"
    android:versionCode="1"
    android:versionName="1.0" >

    <uses-sdk
        android:minSdkVersion="8"
        android:targetSdkVersion="16" />
<uses-permission android:name="android.permission.WRITE_EXTERNAL_STORAGE"/>

    <application
        android:allowBackup="true"
        android:icon="@drawable/ic_launcher"
        android:label="@string/app_name"
        android:theme="@style/AppTheme" >
        <activity
            android:name="com.example.externalstorage.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>

</manifest>

Activity class

Let's write the code to write and read data from the android external storage.

File: MainActivity.java

package com.example.externalstorage;

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 editTextFileName,editTextData;
 Button saveButton,readButton;
 @Override
 protected void onCreate(Bundle savedInstanceState) {
  super.onCreate(savedInstanceState);
  setContentView(R.layout.activity_main);
  
  editTextFileName=(EditText)findViewById(R.id.editText1);
  editTextData=(EditText)findViewById(R.id.editText2);
  saveButton=(Button)findViewById(R.id.button1);
  readButton=(Button)findViewById(R.id.button2);
  
  //Performing action on save button
  saveButton.setOnClickListener(new OnClickListener(){

   @Override
   public void onClick(View arg0) {
    String filename=editTextFileName.getText().toString();
    String data=editTextData.getText().toString();
    
    FileOutputStream fos;
       try {
        File myFile = new File("/sdcard/"+filename);
      myFile.createNewFile();
      FileOutputStream fOut = new FileOutputStream(myFile);
      OutputStreamWriter myOutWriter = new OutputStreamWriter(fOut);
      myOutWriter.append(data);
      myOutWriter.close();
      fOut.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
  readButton.setOnClickListener(new OnClickListener(){

   @Override
   public void onClick(View arg0) {
    String filename=editTextFileName.getText().toString();
    StringBuffer stringBuffer = new StringBuffer();  
    String aDataRow = "";
    String aBuffer = "";
    try {
     File myFile = new File("/sdcard/"+filename);
     FileInputStream fIn = new FileInputStream(myFile);
     BufferedReader myReader = new BufferedReader(
       new InputStreamReader(fIn));
     
     while ((aDataRow = myReader.readLine()) != null) {
      aBuffer += aDataRow + "\n";
     }
     myReader.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.activity_main, menu);
  return true;
 }

}

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