External Storage in Android with Example

Android gives various options for storing apps data which uses a file system similar to the disk-based system on computer platforms

• App-Specific storage: Store data files within internal volume directories or external. These data files are meant only for the app’s use. It uses internal storage directories to save sensitive information such as a username and password that other app should not access.
• Shared Storage: Store data files such as images, audio, video, documents, etc. that the app may need to share with other apps.
• Shared Preferences: Store primitive data type such as integer, float, boolean, string, long in key-value pairs.
• Databases: Store structured data such as user-information(name,  age, phone, email, address, etc.) into private databases.

Developers are advised to use the options available to store data depending upon the space required, reliable data access, and privacy of data. The data files saved over external storage devices are publicly accessible on shared external storage using USB mass storage transfer. Data files stored over external storage using a FileOutputStream object and can be read using a FileInputStream object.

External Storage Availability

In order to avoid crashing the app first, we need to check storage SD Card is available for reading and write operations. The method getExternalStorageState() is used to determine the state of mounted storage media such as SD Card is missing, read-only or readable, and writable. Below is the code snippet which we will use to check the availability of external storage.

Java

boolean isAvailable= false;
boolean isWritable= false;
boolean isReadable= false;
String state = Environment.getExternalStorageState();

if(Environment.MEDIA_MOUNTED.equals(state)) {
  // Operation possible - Read and Write
  isAvailable= true;
  isWritable= true;
  isReadable= true;
} else if (Environment.MEDIA_MOUNTED_READ_ONLY.equals(state)) {
      // Operation possible - Read Only
      isAvailable= true;
      isWritable= false;
      isReadable= true;
} else {
      // SD card not available
      isAvailable = false;
      isWritable= false;
      isReadable= false;
}

Methods to Store data in External Storage

• getExternalStoragePublicDirectory(): This is the present recommended method to keep files public and these files are not deleted even when the app is uninstalled from the system. For eg: Images clicked by the camera are still available even after we uninstall the camera.
• getExternalFilesDir(String type): This method is used to store private data that are specific to the app only. And data are removed as we uninstall the app.
• getExternalStorageDirectory(): This method is not recommended. It is now absolute and it is used to access external storage in older versions, API Level less than 7.

Example

In this example, we would store text data into the external storage and fetch to see that data. A sample GIF is given below to get an idea about what we are going to do in this article. Note that we are going to implement this project using the Java language. 

Step by Step Implementation

Step 1: Create a New Project

To create a new project in Android Studio please refer to How to Create/Start a New Project in Android Studio. Note that select Java as the programming language.

Step 2: Access Permission to External Storage

To read and write data to external storage, the app required WRITE_EXTERNAL_STORAGE and READ_EXTERNAL_STORAGE system permission. These permissions are added to the AndroidManifest.xml file. Add these permissions just after the package name.

XML

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

    <application ... >
        <activity android:name=".MainActivity" ... >
          ...
        </activity>
    </application>
</manifest>

Step 3: Before creating the layout and corresponding java files let’s add a few string attributes which we are using in our layout files

Go to app > res > values > string.xml and insert the following code snippet

XML

<resources>
  ...
    <string name="text_view_data">Enter the Text Data</string>
    <string name="edit_text_data">Enter your information</string>
    <string name="view_button">View Information</string>
    <string name="save_button_public">Save Publicly</string>
    <string name="save_button_private">Save Privately</string>

    <string name="text_view_saved_data">Saved Text Data</string>
    <string name="saved_information">Click to view saved information</string>
    <string name="back_button">Go Back</string>
    <string name="show_button_public">Public Data</string>
    <string name="show_button_private">Private Data</string>
  ...
</resources>

Now go to app > res > values > colors.xml and change the color attributes as following in order to make App Bar more attractive.

XML

<resources>
    <color name="colorPrimary">#0F9D58</color>
    <color name="colorPrimaryDark">#16E37F</color>
    <color name="colorAccent">#03DAC5</color>

    <color name="buttonColor">#0F9D58</color>
    <color name="textColor">#FFFFFF</color>
</resources>

Again go to app > res > drawable and create a new Drawable Resource File and name it as button_layout. In this, we are modifying our button style for a better UX/UI.

XML

<?xml version="1.0" encoding="utf-8"?>
<shape xmlns:android="http://schemas.android.com/apk/res/android"
    android:shape="rectangle">

    <corners
        android:bottomLeftRadius="25dp"
        android:bottomRightRadius="25dp"
        android:radius="50dp"
        android:topLeftRadius="25dp"
        android:topRightRadius="25dp" />

    <padding
        android:bottom="0dp"
        android:left="0dp"
        android:right="0dp"
        android:top="0dp" />

    <size
        android:width="64dp"
        android:height="16dp" />

    <solid android:color="@color/buttonColor" />

</shape>

Step 4: Working with the activity_main.xml file

Go to res > layout > activity_main.xml and write down the following code. In this layout file, we are creating a multiline EditText View for getting the data from users and Buttons to save that data over internal and external storage media.

XML

<?xml version="1.0" encoding="utf-8"?>
<RelativeLayout
    xmlns:android="http://schemas.android.com/apk/res/android"
    xmlns:app="http://schemas.android.com/apk/res-auto"
    xmlns:tools="http://schemas.android.com/tools"
    android:layout_width="match_parent"
    android:layout_height="match_parent"
    tools:context=".MainActivity">

    <Button
        android:id="@+id/saveButton_public"
        android:layout_width="wrap_content"
        android:layout_height="wrap_content"
        android:layout_alignParentEnd="true"
        android:layout_below="@+id/editText_data"
        android:layout_marginEnd="48dp"
        android:layout_marginTop="8dp"
        android:background="@drawable/button_layout"
        android:onClick="savePublicly"
        android:padding="8dp"
        android:text="@string/save_button_public"
        android:textAllCaps="false"
        android:textColor="@color/textColor" />

    <Button
        android:id="@+id/saveButton_private"
        android:layout_width="wrap_content"
        android:layout_height="wrap_content"
        android:layout_alignParentStart="true"
        android:layout_below="@+id/editText_data"
        android:layout_marginStart="48dp"
        android:layout_marginTop="8dp"
        android:layout_toEndOf="@+id/saveButton_public"
        android:background="@drawable/button_layout"
        android:onClick="savePrivately"
        android:padding="8dp"
        android:text="@string/save_button_private"
        android:textAllCaps="false"
        android:textColor="@color/textColor" />

    <Button
        android:id="@+id/viewButton"
        android:layout_width="wrap_content"
        android:layout_height="wrap_content"
        android:layout_below="@+id/saveButton_public"
        android:layout_centerHorizontal="true"
        android:layout_marginTop="16dp"
        android:background="@drawable/button_layout"
        android:onClick="viewInformation"
        android:padding="8dp"
        android:text="@string/view_button"
        android:textAllCaps="false"
        android:textColor="@color/textColor" />

    <EditText
        android:id="@+id/editText_data"
        android:layout_width="match_parent"
        android:layout_height="wrap_content"
        android:layout_below="@+id/textView_data"
        android:layout_centerHorizontal="true"
        android:layout_marginTop="8dp"
        android:autofillHints=""
        android:hint="@string/edit_text_data"
        android:inputType="textMultiLine" />

    <TextView
        android:id="@+id/textView_data"
        android:layout_width="wrap_content"
        android:layout_height="wrap_content"
        android:layout_alignParentTop="true"
        android:layout_centerHorizontal="true"
        android:layout_marginTop="8dp"
        android:text="@string/text_view_data"
        android:textAllCaps="true"
        android:textStyle="bold" />

</RelativeLayout>

Step 5: Working with the MainActivity.java file

In MainActivity we define the functions that handled the onClick behavior of the buttons. And fetch the data from the EditText and save it in external storage publicly and privately. We also display a Toast message of the path where the data is stored.

Java

import android.Manifest;
import android.content.Intent;
import android.os.Bundle;
import android.os.Environment;
import android.view.View;
import android.widget.EditText;
import android.widget.Toast;
import androidx.appcompat.app.AppCompatActivity;
import androidx.core.app.ActivityCompat;
import java.io.File;
import java.io.FileOutputStream;
import java.io.IOException;

public class MainActivity extends AppCompatActivity {

    // After API 23 the permission request for accessing external storage is changed
    // Before API 23 permission request is asked by the user during installation of app
    // After API 23 permission request is asked at runtime
    private int EXTERNAL_STORAGE_PERMISSION_CODE = 23;
    EditText editText;

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

        // findViewById return a view, we need to cast it to EditText View
        editText = (EditText) findViewById(R.id.editText_data);
    }

    public void savePublicly(View view) {
        // Requesting Permission to access External Storage
        ActivityCompat.requestPermissions(this, new String[]{Manifest.permission.READ_EXTERNAL_STORAGE},
                EXTERNAL_STORAGE_PERMISSION_CODE);
        String editTextData = editText.getText().toString();

        // getExternalStoragePublicDirectory() represents root of external storage, we are using DOWNLOADS
        // We can use following directories: MUSIC, PODCASTS, ALARMS, RINGTONES, NOTIFICATIONS, PICTURES, MOVIES
        File folder = Environment.getExternalStoragePublicDirectory(Environment.DIRECTORY_DOWNLOADS);

        // Storing the data in file with name as geeksData.txt
        File file = new File(folder, "geeksData.txt");
        writeTextData(file, editTextData);
        editText.setText("");
    }

    public void savePrivately(View view) {
        String editTextData = editText.getText().toString();

        // Creating folder with name GeeksForGeeks
        File folder = getExternalFilesDir("GeeksForGeeks");

        // Creating file with name gfg.txt
        File file = new File(folder, "gfg.txt");
        writeTextData(file, editTextData);
        editText.setText("");
    }

    public void viewInformation(View view) {
        // Creating an intent to start a new activity
        Intent intent = new Intent(MainActivity.this, ViewInformationActivity.class);
        startActivity(intent);
    }

    // writeTextData() method save the data into the file in byte format
    // It also toast a message "Done/filepath_where_the_file_is_saved"
    private void writeTextData(File file, String data) {
        FileOutputStream fileOutputStream = null;
        try {
            fileOutputStream = new FileOutputStream(file);
            fileOutputStream.write(data.getBytes());
            Toast.makeText(this, "Done" + file.getAbsolutePath(), Toast.LENGTH_SHORT).show();
        } catch (Exception e) {
            e.printStackTrace();
        } finally {
            if (fileOutputStream != null) {
                try {
                    fileOutputStream.close();
                } catch (IOException e) {
                    e.printStackTrace();
                }
            }
        }
    }
}

Step 6: Create a new Empty Activity

We will create a new activity and name it ViewInformationActivity. We use this activity to display the saved data from the external storage. So, first, we create a layout for this activity similar to the MainActivity layout. activity_view_information.xml layout code snippet:

XML

<?xml version="1.0" encoding="utf-8"?>
<RelativeLayout
       xmlns:android="http://schemas.android.com/apk/res/android"
    xmlns:app="http://schemas.android.com/apk/res-auto"
    xmlns:tools="http://schemas.android.com/tools"
    android:layout_width="match_parent"
    android:layout_height="match_parent"
    tools:context=".ViewInformationActivity">

    <Button
        android:id="@+id/showButton_public"
        android:layout_width="wrap_content"
        android:layout_height="wrap_content"
        android:layout_alignParentEnd="true"
        android:layout_below="@+id/textView_get_saved_data"
        android:layout_marginEnd="48dp"
        android:layout_marginTop="8dp"
        android:background="@drawable/button_layout"
        android:onClick="showPublicData"
        android:padding="8dp"
        android:text="@string/show_button_public"
        android:textAllCaps="false"
        android:textColor="@color/textColor" />

    <Button
        android:id="@+id/showButton_private"
        android:layout_width="wrap_content"
        android:layout_height="wrap_content"
        android:layout_alignParentStart="true"
        android:layout_below="@+id/textView_get_saved_data"
        android:layout_marginStart="48dp"
        android:layout_marginTop="8dp"
        android:layout_toEndOf="@+id/showButton_public"
        android:background="@drawable/button_layout"
        android:onClick="showPrivateData"
        android:padding="8dp"
        android:text="@string/show_button_private"
        android:textAllCaps="false"
        android:textColor="@color/textColor" />

    <Button
        android:id="@+id/goBackButton"
        android:layout_width="wrap_content"
        android:layout_height="wrap_content"
        android:layout_below="@+id/showButton_public"
        android:layout_centerHorizontal="true"
        android:layout_marginTop="16dp"
        android:background="@drawable/button_layout"
        android:onClick="back"
        android:padding="8dp"
        android:text="@string/back_button"
        android:textAllCaps="false"
        android:textColor="@color/textColor" />

    <TextView
        android:id="@+id/textView_get_saved_data"
        android:layout_width="match_parent"
        android:layout_height="wrap_content"
        android:layout_below="@+id/textView_saved_data"
        android:layout_marginTop="8dp"
        android:gravity="center"
        android:hint="@string/saved_information" />

    <TextView
        android:id="@+id/textView_saved_data"
        android:layout_width="match_parent"
        android:layout_height="wrap_content"
        android:layout_marginTop="8dp"
        android:gravity="center"
        android:text="@string/text_view_saved_data"
        android:textAllCaps="true"
        android:textStyle="bold" />

</RelativeLayout>

Now, we will create a corresponding java code for ViewInformationActivity. In this, we define methods showPublicData() and showPrivateData() over buttons that will fetch the data from the files saved to external storage and add the data to buffer, and then populate the data to TextView in order to show them. ViewInformationAcitity.java code snippet:

Java

import android.content.Intent;
import android.os.Bundle;
import android.os.Environment;
import android.view.View;
import android.widget.TextView;
import androidx.appcompat.app.AppCompatActivity;
import java.io.File;
import java.io.FileInputStream;
import java.io.IOException;

public class ViewInformationActivity extends AppCompatActivity {

    TextView textView;

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

        // findViewById returns a view, we need to cast it into TextView
        textView = (TextView) findViewById(R.id.textView_get_saved_data);
    }

    public void showPublicData(View view) {
        // Accessing the saved data from the downloads folder
        File folder = Environment.getExternalStoragePublicDirectory(Environment.DIRECTORY_DOWNLOADS);

        // geeksData represent the file data that is saved publicly
        File file = new File(folder, "geeksData.txt");
        String data = getdata(file);
        if (data != null) {
            textView.setText(data);
        } else {
            textView.setText("No Data Found");
        }
    }

    public void showPrivateData(View view) {

        // GeeksForGeeks represent the folder name to access privately saved data
        File folder = getExternalFilesDir("GeeksForGeeks");

        // gft.txt is the file that is saved privately
        File file = new File(folder, "gfg.txt");
        String data = getdata(file);
        if (data != null) {
            textView.setText(data);
        } else {
            textView.setText("No Data Found");
        }
    }

    public void back(View view) {
        Intent intent = new Intent(ViewInformationActivity.this, MainActivity.class);
        startActivity(intent);
    }

    // getdata() is the method which reads the data
    // the data that is saved in byte format in the file
    private String getdata(File myfile) {
        FileInputStream fileInputStream = null;
        try {
            fileInputStream = new FileInputStream(myfile);
            int i = -1;
            StringBuffer buffer = new StringBuffer();
            while ((i = fileInputStream.read()) != -1) {
                buffer.append((char) i);
            }
            return buffer.toString();
        } catch (Exception e) {
            e.printStackTrace();
        } finally {
            if (fileInputStream != null) {
                try {
                    fileInputStream.close();
                } catch (IOException e) {
                    e.printStackTrace();
                }
            }
        }
        return null;
    }
}

Output: Run on Emulator