Android External Storage – Read, Write, Save File

Filed Under: Android

Android external storage can be used to write and save data, read configuration files etc. This article is continuation of the Android Internal Storage tutorial in the series of tutorials on structured data storage in android.

Android External Storage

External storage such as SD card can also store application data, there’s no security enforced upon files you save to the external storage.
In general there are two types of External Storage:

  • Primary External Storage: In built shared storage which is “accessible by the user by plugging in a USB cable and mounting it as a drive on a host computer”. Example: When we say Nexus 5 32 GB.
  • Secondary External Storage: Removable storage. Example: SD Card

All applications can read and write files placed on the external storage and the user can remove them. We need to check if the SD card is available and if we can write to it. Once we’ve checked that the external storage is available only then we can write to it else the save button would be disabled.

Android External Storage Example Project Structure

android external storage

Firstly, we need to make sure that the application has permission to read and write data to the users SD card, so lets open up the AndroidManifest.xml and add the following permissions:


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

Also, external storage may be tied up by the user having mounted it as a USB storage device. So we need to check if the external storage is available and is not read only.


if (!isExternalStorageAvailable() || isExternalStorageReadOnly()) {  
   saveButton.setEnabled(false);
  }  

private static boolean isExternalStorageReadOnly() {  
  String extStorageState = Environment.getExternalStorageState();  
  if (Environment.MEDIA_MOUNTED_READ_ONLY.equals(extStorageState)) {  
   return true;  
  }  
  return false;  
 }  
 
 private static boolean isExternalStorageAvailable() {  
  String extStorageState = Environment.getExternalStorageState();  
  if (Environment.MEDIA_MOUNTED.equals(extStorageState)) {  
   return true;  
  }  
  return false;  
 }  

getExternalStorageState() is a static method of Environment to determine if external storage is presently available or not. As you can see if the condition is false we’ve disabled the save button.

Android External Storage Example Code

The activity_main.xml layout is defined as follows:


<?xml version="1.0" encoding="utf-8"?>
<LinearLayout xmlns:android="http://schemas.android.com/apk/res/android"
    android:layout_width="fill_parent" android:layout_height="fill_parent"
    android:orientation="vertical">

    <TextView android:layout_width="fill_parent"
        android:layout_height="wrap_content"
        android:text="Reading and Writing to External Storage"
        android:textSize="24sp"/>

    <EditText android:id="@+id/myInputText"
        android:layout_width="match_parent"
        android:layout_height="wrap_content"
        android:ems="10" android:lines="5"
        android:minLines="3" android:gravity="top|left"
        android:inputType="textMultiLine">

        <requestFocus />
    </EditText>

    <LinearLayout
    android:layout_width="match_parent" android:layout_height="wrap_content"
    android:orientation="horizontal"
        android:weightSum="1.0"
        android:layout_marginTop="20dp">

    <Button android:id="@+id/saveExternalStorage"
        android:layout_width="match_parent"
        android:layout_height="wrap_content"
        android:text="SAVE"
        android:layout_weight="0.5"/>

    <Button android:id="@+id/getExternalStorage"
        android:layout_width="match_parent"
        android:layout_height="wrap_content"
        android:layout_weight="0.5"
        android:text="READ" />

    </LinearLayout>

    <TextView android:id="@+id/response"
        android:layout_width="wrap_content"
        android:layout_height="wrap_content" android:padding="5dp"
        android:text=""
        android:textAppearance="?android:attr/textAppearanceMedium" />

</LinearLayout>

Here apart from the save and read from external storage buttons we display the response of saving/reading to/from an external storage in a textview unlike in the previous tutorial where android toast was displayed.

The MainActivity.java class is given below:


package com.journaldev.externalstorage;

import java.io.BufferedReader;
import java.io.DataInputStream;
import java.io.File;
import java.io.FileInputStream;
import java.io.FileOutputStream;
import java.io.IOException;
import java.io.InputStreamReader;
import android.os.Bundle;
import android.app.Activity;
import android.os.Environment;
import android.view.View;
import android.view.View.OnClickListener;
import android.widget.Button;
import android.widget.EditText;
import android.widget.TextView;


public class MainActivity extends Activity {
    EditText inputText;
    TextView response;
    Button saveButton,readButton;

    private String filename = "SampleFile.txt";
    private String filepath = "MyFileStorage";
    File myExternalFile;
    String myData = "";

    @Override
    protected void onCreate(Bundle savedInstanceState) {
        super.onCreate(savedInstanceState);
        setContentView(R.layout.activity_main);

        inputText = (EditText) findViewById(R.id.myInputText);
        response = (TextView) findViewById(R.id.response);


         saveButton =
                (Button) findViewById(R.id.saveExternalStorage);
        saveButton.setOnClickListener(new OnClickListener() {
            @Override
            public void onClick(View v) {
                try {
                    FileOutputStream fos = new FileOutputStream(myExternalFile);
                    fos.write(inputText.getText().toString().getBytes());
                    fos.close();
                } catch (IOException e) {
                    e.printStackTrace();
                }
                inputText.setText("");
                response.setText("SampleFile.txt saved to External Storage...");
            }
        });

        readButton = (Button) findViewById(R.id.getExternalStorage);
        readButton.setOnClickListener(new OnClickListener() {
            @Override
            public void onClick(View v) {
                try {
                    FileInputStream fis = new FileInputStream(myExternalFile);
                    DataInputStream in = new DataInputStream(fis);
                    BufferedReader br =
                            new BufferedReader(new InputStreamReader(in));
                    String strLine;
                    while ((strLine = br.readLine()) != null) {
                        myData = myData + strLine;
                    }
                    in.close();
                } catch (IOException e) {
                    e.printStackTrace();
                }
                inputText.setText(myData);
                response.setText("SampleFile.txt data retrieved from Internal Storage...");
            }
        });

        if (!isExternalStorageAvailable() || isExternalStorageReadOnly()) {
            saveButton.setEnabled(false);
        }
        else {
            myExternalFile = new File(getExternalFilesDir(filepath), filename);
        }


    }
    private static boolean isExternalStorageReadOnly() {
        String extStorageState = Environment.getExternalStorageState();
        if (Environment.MEDIA_MOUNTED_READ_ONLY.equals(extStorageState)) {
            return true;
        }
        return false;
    }

    private static boolean isExternalStorageAvailable() {
        String extStorageState = Environment.getExternalStorageState();
        if (Environment.MEDIA_MOUNTED.equals(extStorageState)) {
            return true;
        }
        return false;
    }


}
  1. Environment.getExternalStorageState(): returns path to internal SD mount point like “/mnt/sdcard”
  2. getExternalFilesDir(): It returns the path to files folder inside Android/data/data/application_package/ on the SD card. It is used to store any required files for your app (like images downloaded from web or cache files). Once the app is uninstalled, any data stored in this folder is gone too.

Also if the external storage is not available we disable the save button using the if condition that was discussed earlier in this tutorial.

Below is our application running in android emulator, where we are writing data to file and then reading it.

android external storage example read write save file

Note: Make sure your Android Emulator is configured such that it has a SD card as shown in the image dialog from AVD below. Go to Tools->Android->Android Virtual Device, edit configurations->Show Advance Settings.

android external storage config, android save file to external storage

This brings an end to this tutorial. We’ll discuss storage using Shared Preferences in the next tutorial. You can download the final Android External Storage Project from the below link.

Comments

  1. Govind says:

    I want to save data in sqlite for saving android app data offline and sync the saved data when online. please help.

  2. NicolasNy says:

    Nice, but this example only use primary external storage. What about Secondary External Storage as you comment at the top of this post?

  3. ananthirathna@gmai.com says:

    please post mediaplayer example.

    String mediaPath = “/sdcard/Omnamashivaya.mp3″;
    Uri uriPath = Uri.parse(mediaPath);

    MediaPlayer player = new MediaPlayer();
    try {
    player.setDataSource(getApplicationContext(),uriPath);
    player.prepare();
    player.start();

    Toast.makeText(getApplicationContext(),”Start to play”,Toast.LENGTH_LONG).show();

    } catch (IOException e) {
    e.printStackTrace();
    }

    i got below exception

    W/MediaPlayer: Couldn’t open /sdcard/Omnamashivaya.mp3: java.io.FileNotFoundException: No content provider: /sdcard/Omnamashivaya.mp3
    W/System.err: java.io.FileNotFoundException: /sdcard/Omnamashivaya.mp3 (Permission denied)
    at java.io.FileInputStream.open0(Native Method)
    at java.io.FileInputStream.open(FileInputStream.java:200)
    at java.io.FileInputStream.(FileInputStream.java:150)
    at android.media.MediaPlayer.setDataSource(MediaPlayer.java:1182)
    W/System.err: at android.media.MediaPlayer.setDataSource(MediaPlayer.java:1160)
    at android.media.MediaPlayer.setDataSource(MediaPlayer.java:1078)
    W/System.err: at android.media.MediaPlayer.setDataSource(MediaPlayer.java:1003)
    at com.randy.chennaitourism.MainActivity$override.onCreate(MainActivity.java:35)
    at com.randy.chennaitourism.MainActivity$override.access$dispatch(Unknown Source:74)
    at com.randy.chennaitourism.MainActivity.onCreate(Unknown Source:15)
    at android.app.Activity.performCreate(Activity.java:7009)
    at android.app.Activity.performCreate(Activity.java:7000)
    at android.app.Instrumentation.callActivityOnCreate(Instrumentation.java:1214)
    at android.app.ActivityThread.performLaunchActivity(ActivityThread.java:2731)
    at android.app.ActivityThread.handleLaunchActivity(ActivityThread.java:2856)
    at android.app.ActivityThread.handleRelaunchActivity(ActivityThread.java:4699)
    W/System.err: at android.app.ActivityThread.-wrap18(Unknown Source:0)
    at android.app.ActivityThread$H.handleMessage(ActivityThread.java:1595)
    at android.os.Handler.dispatchMessage(Handler.java:106)
    at android.os.Looper.loop(Looper.java:164)
    at android.app.ActivityThread.main(ActivityThread.java:6494)

  4. satendra singh says:

    Ok i got it, e.g. in SDCARD the path android/data/app_name/files/MyFileStorage exists and the folder is empty.

    Android SDK built for x86 path android/data/app_name/files/MyFileStorage/SampleFile.txt exists, but what is the difference? :/ And why is the file not on the sdcard? 🙂
    Pla reply

  5. silverlokk says:

    if (Environment.MEDIA_MOUNTED_READ_ONLY.equals(extStorageState)) {
    return true;
    }
    return false;

    can be rewritten as:

    return Environment.MEDIA_MOUNTED_READ_ONLY.equals(extStorageState)

    Similarly, any if () { return true; } return false; can be rewritten return ()

    1. silverlokk says:

      Darn, I was afraid the comment box would strip out the left-angle brackets:

      if (<boolean-expression>) {return true;} return false; can be rewritten return (<boolean-expression>);

      Also forgot to end the statement with a semi-colon, so just as well 🙂

  6. bagher says:

    hi dears
    im really happy to see these useful tutorial which you put theme in your site
    they are really useful and of clear summary
    thx alot

  7. khushbu says:

    Hello,
    nice tutorial!!!
    Even I was unable to find file path. I just debugged the app & tried this myExternalFile.getAbsolutePath(); & yipeee I found the correct file path.

    For me path is /storage/emulated/0/Android/data/your package name/files/MyFileStorage/SampleFile.txt

  8. Farhan says:

    Hello, great tutorial but you only covered the primary external storage, what about the secondary one?

  9. pradana says:

    thanks for share this 😀

  10. TRINH TRINH says:

    hi you!

    How to export data saved in sqlite to txt file
    Thank you !

    1. venkittu says:

      I also have some doubt….

  11. Matthew Johnson says:

    It is irritating beyond belief that a popup for “FREE eBook” covers up part of the display without even showing a Close button/box. Rest assured I will never buy anything advertised on this web site because of htat.

  12. babu says:

    Layout and layout parameters are not connected to java file in the above code .

  13. hackerassh says:

    hii sir I want make app for English grammar can u tell how can I do it sorry for my poor English

  14. Ankur Bhoot says:

    hi anupam ,
    i need your help if possible.
    i have get image using json web services.
    now i need to download this when click download button and image an store in my mobile storage .
    how can i perform this task.
    YOU CAN REPLY IN MY EMAIL .

  15. Hugo says:

    Hey your tutorial is awesome and working but i cant find the file, the folder “MyFileStorage” is empty but it’s still working… Can you tell me where i can find the file?

    1. Hugo says:

      Ok i got it, e.g. in SDCARD the path android/data/app_name/files/MyFileStorage exists and the folder is empty.

      Android SDK built for x86 path android/data/app_name/files/MyFileStorage/SampleFile.txt exists, but what is the difference? :/ And why is the file not on the sdcard? 🙂

  16. rudolf says:

    hi anupam,

    thank you for your clear explanation and coding
    -and you made me nervous, when i received the text toast:
    ” read from internal storage ” ( its a typo )
    ha: its still the external – i am happy.
    i like to buy you a drink!

    thank you
    rudolf
    hallerhandel@gmail.com

  17. Hanan says:

    Thank You!

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