Kotlin Android Read and Write External Storage

Android External Storage is the memory space in which we perform read and write operation. Files in the external storage are stored in /sdcard or /storage folder etc. The files which are saved in the external storage is readable and can be modified by the user.

Before accessing the file in external storage in our application, we should check the availability of the external storage in our device.

Write to File in External Storage

The java.io package offers openFileOutput() method which returns the instance of FileOutputStream class to write the file in external storage of the device. To acquire a directory that's used by only your app by calling getExternalFilesDir(). To write the data into the file call the FileOutputStream .write() method.

var myExternalFile:File = File(getExternalFilesDir(filepath),fileName)
 try {
     val fileOutPutStream = FileOutputStream(myExternalFile)
     fileOutPutStream.write(fileContent.toByteArray())
     fileOutPutStream.close()
 } catch (e: IOException) {
     e.printStackTrace()
 }

Read File content from External Storage

The java.io package offers openFileInput() method which returns the instance of FileInputStream class and read the file from the external storage of the device. To read the data from file call the BufferedReader().readLine().

var myExternalFile:File = File(getExternalFilesDir(filepath), fileName)
val filename = fileName.text.toString()
myExternalFile = File(getExternalFilesDir(filepath),filename) 
    var fileInputStream =FileInputStream(myExternalFile)
    var inputStreamReader: InputStreamReader = InputStreamReader(fileInputStream)
    val bufferedReader: BufferedReader = BufferedReader(inputStreamReader)
    val stringBuilder: StringBuilder = StringBuilder()
    var text: String? = null
    while ({ text = bufferedReader.readLine(); text }() != null) {
        stringBuilder.append(text)
    }
    fileInputStream.close()

External Storage Access Permission

Add the following permission in AndroidManifest.xml file.

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

Kotlin Android Read and Write External Storage Example

In this example, we will write the data to file inside the external storage and read the same file content from same external storage.

activity_main.xml

Add the following code in the activity_main.xml file. In this file, add two EditText for input file name, file content and two Button for saving and view file content.

<?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="example.javatpoint.com.kotlinexternalstoragereadwrite.MainActivity">


    <TextView
        android:id="@+id/textView"
        android:layout_width="wrap_content"
        android:layout_height="wrap_content"
        android:layout_alignLeft="@+id/textView2"
        android:layout_alignParentTop="true"
        android:layout_alignStart="@+id/textView2"
        android:layout_marginTop="68dp"
        android:text="File Name"
        android:textAppearance="@style/Base.TextAppearance.AppCompat.Medium"
        app:layout_constraintBottom_toBottomOf="parent"
        app:layout_constraintEnd_toEndOf="parent"
        app:layout_constraintHorizontal_bias="0.027"
        app:layout_constraintStart_toStartOf="parent"
        app:layout_constraintTop_toTopOf="parent"
        app:layout_constraintVertical_bias="0.065" />

    <TextView
        android:id="@+id/textView2"
        android:layout_width="wrap_content"
        android:layout_height="wrap_content"
        android:layout_alignBottom="@+id/editTextData"
        android:layout_alignParentLeft="true"
        android:layout_alignParentStart="true"
        android:layout_marginBottom="36dp"
        android:layout_marginLeft="50dp"
        android:layout_marginStart="50dp"
        android:text="File Data"
        android:textAppearance="@style/Base.TextAppearance.AppCompat.Medium"
        app:layout_constraintBottom_toBottomOf="parent"
        app:layout_constraintEnd_toEndOf="parent"
        app:layout_constraintHorizontal_bias="0.027"
        app:layout_constraintStart_toStartOf="parent"
        app:layout_constraintTop_toBottomOf="@+id/textView"
        app:layout_constraintVertical_bias="0.167" />

    <EditText
        android:id="@+id/editTextFile"
        android:layout_width="wrap_content"
        android:layout_height="wrap_content"
        android:layout_alignLeft="@+id/editTextData"
        android:layout_alignStart="@+id/editTextData"
        android:layout_alignTop="@+id/textView"
        android:ems="10"
        android:inputType="none" />

    <EditText
        android:id="@+id/editTextData"
        android:layout_width="wrap_content"
        android:layout_height="wrap_content"
        android:layout_alignParentEnd="true"
        android:layout_alignParentRight="true"
        android:layout_below="@+id/editTextFile"
        android:layout_marginEnd="37dp"
        android:layout_marginRight="37dp"
        android:layout_marginTop="30dp"
        android:ems="10"
        android:inputType="none"
        android:lines="5" />

    <Button
        android:id="@+id/button_save"
        android:layout_width="wrap_content"
        android:layout_height="wrap_content"
        android:layout_alignParentBottom="true"
        android:layout_marginBottom="68dp"
        android:layout_toLeftOf="@+id/editTextData"
        android:layout_toStartOf="@+id/editTextData"
        android:text="Save" />

    <Button
        android:id="@+id/button_view"
        android:layout_width="wrap_content"
        android:layout_height="wrap_content"
        android:layout_alignBottom="@+id/button_save"
        android:layout_alignEnd="@+id/editTextData"
        android:layout_alignRight="@+id/editTextData"
        android:layout_marginEnd="43dp"
        android:layout_marginRight="43dp"
        android:text="View" />

</RelativeLayout>

MainActivity.kt

Add the following code in the MainActivity.kt class. In this class, we are saving the file name and data inside external storage by clicking the save button and retrieving the file content by clicking the view button.

package example.javatpoint.com.kotlinexternalstoragereadwrite

import android.support.v7.app.AppCompatActivity
import android.os.Bundle
import android.view.View
import android.widget.Button
import android.widget.EditText
import android.widget.Toast
import android.os.Environment
import java.io.*

class MainActivity : AppCompatActivity() {
    private val filepath = "MyFileStorage"
    internal var myExternalFile: File?=null
    private val isExternalStorageReadOnly: Boolean get() {
        val extStorageState = Environment.getExternalStorageState()
        return if (Environment.MEDIA_MOUNTED_READ_ONLY.equals(extStorageState)) {
                true
        } else {
                false
        }
    }
    private val isExternalStorageAvailable: Boolean get() {
        val extStorageState = Environment.getExternalStorageState()
        return if (Environment.MEDIA_MOUNTED.equals(extStorageState)) {
            true
        } else{
            false
        }
    }

    override fun onCreate(savedInstanceState: Bundle?) {
        super.onCreate(savedInstanceState)
        setContentView(R.layout.activity_main)
        val fileName = findViewById(R.id.editTextFile) as EditText
        val fileData = findViewById(R.id.editTextData) as EditText
        val saveButton = findViewById<Button>(R.id.button_save) as Button
        val viewButton = findViewById(R.id.button_view) as Button

        saveButton.setOnClickListener(View.OnClickListener {
           myExternalFile = File(getExternalFilesDir(filepath), fileName.text.toString())
            try {
                val fileOutPutStream = FileOutputStream(myExternalFile)
                fileOutPutStream.write(fileData.text.toString().toByteArray())
                fileOutPutStream.close()
            } catch (e: IOException) {
                e.printStackTrace()
            }
            Toast.makeText(applicationContext,"data save",Toast.LENGTH_SHORT).show()
        })
        viewButton.setOnClickListener(View.OnClickListener {
           myExternalFile = File(getExternalFilesDir(filepath), fileName.text.toString())

           val filename = fileName.text.toString()
           myExternalFile = File(getExternalFilesDir(filepath),filename)
           if(filename.toString()!=null && filename.toString().trim()!=""){
               var fileInputStream =FileInputStream(myExternalFile)
               var inputStreamReader: InputStreamReader = InputStreamReader(fileInputStream)
               val bufferedReader: BufferedReader = BufferedReader(inputStreamReader)
               val stringBuilder: StringBuilder = StringBuilder()
               var text: String? = null
               while ({ text = bufferedReader.readLine(); text }() != null) {
                   stringBuilder.append(text)
               }
               fileInputStream.close()
               //Displaying data on EditText
               Toast.makeText(applicationContext,stringBuilder.toString(),Toast.LENGTH_SHORT).show()
           }
        })

        if (!isExternalStorageAvailable || isExternalStorageReadOnly) {
            saveButton.isEnabled = false
        }
    }
}

AndroidManifest.xml

<?xml version="1.0" encoding="utf-8"?>
<manifest xmlns:android="http://schemas.android.com/apk/res/android"
    package="example.javatpoint.com.kotlinexternalstoragereadwrite">
    <uses-permission android:name="android.permission.READ_EXTERNAL_STORAGE"/>
    <uses-permission android:name="android.permission.WRITE_EXTERNAL_STORAGE"/>
    <application
        android:allowBackup="true"
        android:icon="@mipmap/ic_launcher"
        android:label="@string/app_name"
        android:roundIcon="@mipmap/ic_launcher_round"
        android:supportsRtl="true"
        android:theme="@style/AppTheme">
        <activity android:name=".MainActivity">
            <intent-filter>
                <action android:name="android.intent.action.MAIN" />

                <category android:name="android.intent.category.LAUNCHER" />
            </intent-filter>
        </activity>
    </application>

</manifest>

Output: