Reading & Writing File in Android

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Hello Friends, Today I am writing this post to share that how to read and write file to external storage in Android. In the latest version of android Marshmallow, we cannot read and write file directly in external storage even we declare permission in manifest file but in lower version we can use external storage after declaring permission in manifest file.

To access external storage in Marshmallow we need to take permission at runtime. From the code below we can read & write file to external storage on any android version.

AndroidManifest.xml

<?xml version="1.0" encoding="utf-8"?>
<manifest xmlns:android="http://schemas.android.com/apk/res/android"
    package="com.zatackcoder.storefile">

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

    <application
        android:allowBackup="true"
        android:icon="@mipmap/ic_launcher"
        android:label="@string/app_name"
        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>

<?xml version="1.0" encoding="utf-8"?>

<manifest xmlns:android="http://schemas.android.com/apk/res/android"

package="com.zatackcoder.storefile">

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

<application

android:allowBackup="true"

android:icon="@mipmap/ic_launcher"

android:label="@string/app_name"

android:supportsRtl="true"

android:theme="@style/AppTheme">

<intent-filter>

</intent-filter>

</activity>

</application>

</manifest>

activity_main.xml

<?xml version="1.0" encoding="utf-8"?>
<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"
    android:paddingBottom="@dimen/activity_vertical_margin"
    android:paddingLeft="@dimen/activity_horizontal_margin"
    android:paddingRight="@dimen/activity_horizontal_margin"
    android:paddingTop="@dimen/activity_vertical_margin"
    tools:context="com.zatackcoder.storefile.MainActivity">

    <TextView
        android:layout_width="match_parent"
        android:layout_height="wrap_content"
        android:text="File Content and Information will be shown here"
        android:id="@+id/data_and_info" />

    <Button
        android:layout_width="wrap_content"
        android:layout_height="wrap_content"
        android:text="Write"
        android:id="@+id/writeB"
        android:layout_alignParentBottom="true"
        android:layout_toLeftOf="@+id/readB"
        android:layout_toStartOf="@+id/readB" />

    <Button
        android:layout_width="wrap_content"
        android:layout_height="wrap_content"
        android:text="Read"
        android:id="@+id/readB"
        android:layout_marginRight="74dp"
        android:layout_marginEnd="74dp"
        android:layout_alignTop="@+id/writeB"
        android:layout_alignRight="@+id/data_and_info"
        android:layout_alignEnd="@+id/data_and_info" />
</RelativeLayout>

<?xml version="1.0" encoding="utf-8"?>

<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"

android:paddingBottom="@dimen/activity_vertical_margin"

android:paddingLeft="@dimen/activity_horizontal_margin"

android:paddingRight="@dimen/activity_horizontal_margin"

android:paddingTop="@dimen/activity_vertical_margin"

tools:context="com.zatackcoder.storefile.MainActivity">

<TextView

android:layout_width="match_parent"

android:layout_height="wrap_content"

android:text="File Content and Information will be shown here"

android:id="@+id/data_and_info" />

<Button

android:layout_width="wrap_content"

android:layout_height="wrap_content"

android:text="Write"

android:id="@+id/writeB"

android:layout_alignParentBottom="true"

android:layout_toLeftOf="@+id/readB"

android:layout_toStartOf="@+id/readB" />

<Button

android:layout_width="wrap_content"

android:layout_height="wrap_content"

android:text="Read"

android:id="@+id/readB"

android:layout_marginRight="74dp"

android:layout_marginEnd="74dp"

android:layout_alignTop="@+id/writeB"

android:layout_alignRight="@+id/data_and_info"

android:layout_alignEnd="@+id/data_and_info" />

</RelativeLayout>

MainActivity.java

package com.zatackcoder.storefile;

import android.Manifest;
import android.content.pm.PackageManager;
import android.os.Build;
import android.os.Environment;
import android.support.v4.app.ActivityCompat;
import android.support.v7.app.AppCompatActivity;
import android.os.Bundle;
import android.view.View;
import android.widget.Button;
import android.widget.TextView;
import android.widget.Toast;

import java.io.File;
import java.io.FileInputStream;
import java.io.FileNotFoundException;
import java.io.FileOutputStream;
import java.io.IOException;

public class MainActivity extends AppCompatActivity implements ActivityCompat.OnRequestPermissionsResultCallback{

    TextView dataAndInfoTV;

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

        dataAndInfoTV = (TextView)findViewById(R.id.data_and_info);

        Button writeB = (Button)findViewById(R.id.writeB);
        Button readB = (Button)findViewById(R.id.readB);

        writeB.setOnClickListener(new View.OnClickListener(){

            @Override
            public void onClick(View v) {
                if(isExternalStorageWritable()){
                    Toast.makeText(getApplicationContext(), "External Storage Writable", Toast.LENGTH_LONG).show();
                    File file = new File(Environment.getExternalStorageDirectory(),"storagefile");
                    if(!file.exists()){
                        if(file.mkdir()){
                            Toast.makeText(getApplicationContext(), "Directory created", Toast.LENGTH_LONG).show();
                        }

                    } else {
                        Toast.makeText(getApplicationContext(), "Directory already available", Toast.LENGTH_LONG).show();
                        dataAndInfoTV.setText(file.getAbsolutePath());
                    }

                    File newfile = new File(file.getAbsolutePath()+"/testfile.txt");
                    try {
                        if(!newfile.exists()){
                            newfile.createNewFile();
                        }
                        FileOutputStream outputStream = new FileOutputStream(newfile);
                        outputStream.write("This is file content".getBytes());
                        outputStream.close();
                        Toast.makeText(getApplicationContext(), "File created", Toast.LENGTH_LONG).show();
                    } catch (Exception e) {
                        Toast.makeText(getApplicationContext(), "Error while creating File", Toast.LENGTH_LONG).show();
                    }
                } else {
                    Toast.makeText(getApplicationContext(), "External Storage Not Writable", Toast.LENGTH_LONG).show();
                }
            }
        });

        readB.setOnClickListener(new View.OnClickListener(){

            @Override
            public void onClick(View v) {
                File file = new File(Environment.getExternalStorageDirectory().getAbsolutePath()+"/storagefile/testfile.txt");
                if(file != null && file.exists()){

                    try {
                        FileInputStream fis = new FileInputStream(file);
                        String str = "";
                        int data;
                        while((data = fis.read()) != -1){
                            str += (char)data;
                        }
                        dataAndInfoTV.setText(str);
                    } catch (FileNotFoundException e) {
                        Toast.makeText(getApplicationContext(), "File not found", Toast.LENGTH_LONG).show();
                    } catch (IOException e) {
                        Toast.makeText(getApplicationContext(), "Error while reading File", Toast.LENGTH_LONG).show();
                    }
                } else {
                    Toast.makeText(getApplicationContext(), "File does not exists", Toast.LENGTH_LONG).show();
                }
            }
        });

        //Getting permission for Marshmallow or higher version at runtime
        getExternalStorageWritePermission();

    }


    /* Checks if external storage is available for read and write */
    private boolean isExternalStorageWritable() {
        String state = Environment.getExternalStorageState();
        if (Environment.MEDIA_MOUNTED.equals(state)) {
            return true;
        }
        return false;
    }

    private void getExternalStorageWritePermission(){
        if (Build.VERSION.SDK_INT >= Build.VERSION_CODES.M) {
            if(checkSelfPermission(Manifest.permission.WRITE_EXTERNAL_STORAGE) != PackageManager.PERMISSION_GRANTED){
                // Should we show an explanation?
                if (shouldShowRequestPermissionRationale(Manifest.permission.WRITE_EXTERNAL_STORAGE)) {
                } else {
                    //Requesting permission.
                    ActivityCompat.requestPermissions(this, new String[]{Manifest.permission.WRITE_EXTERNAL_STORAGE}, 1);
                }

            }
        }
    }

    @Override //Override from ActivityCompat.OnRequestPermissionsResultCallback Interface
    public void onRequestPermissionsResult(int requestCode, String[] permissions, int[] grantResults) {
        switch (requestCode) {
            case 1: {
                // If request is cancelled, the result arrays are empty.
                if (grantResults.length > 0 && grantResults[0] == PackageManager.PERMISSION_GRANTED) {
                    // permission granted
                }
                return;
            }
        }
    }
}

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package com.zatackcoder.storefile;

import android.Manifest;

import android.content.pm.PackageManager;

import android.os.Build;

import android.os.Environment;

import android.support.v4.app.ActivityCompat;

import android.support.v7.app.AppCompatActivity;

import android.os.Bundle;

import android.view.View;

import android.widget.Button;

import android.widget.TextView;

import android.widget.Toast;

import java.io.File;

import java.io.FileInputStream;

import java.io.FileNotFoundException;

import java.io.FileOutputStream;

import java.io.IOException;

public class MainActivity extends AppCompatActivity implements ActivityCompat.OnRequestPermissionsResultCallback{

TextView dataAndInfoTV;

@Override

protected void onCreate(Bundle savedInstanceState) {

super.onCreate(savedInstanceState);

setContentView(R.layout.activity_main);

dataAndInfoTV = (TextView)findViewById(R.id.data_and_info);

Button writeB = (Button)findViewById(R.id.writeB);

Button readB = (Button)findViewById(R.id.readB);

writeB.setOnClickListener(new View.OnClickListener(){

@Override

public void onClick(View v) {

if(isExternalStorageWritable()){

Toast.makeText(getApplicationContext(), "External Storage Writable", Toast.LENGTH_LONG).show();

File file = new File(Environment.getExternalStorageDirectory(),"storagefile");

if(!file.exists()){

if(file.mkdir()){

Toast.makeText(getApplicationContext(), "Directory created", Toast.LENGTH_LONG).show();

}

} else {

Toast.makeText(getApplicationContext(), "Directory already available", Toast.LENGTH_LONG).show();

dataAndInfoTV.setText(file.getAbsolutePath());

}

File newfile = new File(file.getAbsolutePath()+"/testfile.txt");

try {

if(!newfile.exists()){

newfile.createNewFile();

}

FileOutputStream outputStream = new FileOutputStream(newfile);

outputStream.write("This is file content".getBytes());

outputStream.close();

Toast.makeText(getApplicationContext(), "File created", Toast.LENGTH_LONG).show();

} catch (Exception e) {

Toast.makeText(getApplicationContext(), "Error while creating File", Toast.LENGTH_LONG).show();

}

} else {

Toast.makeText(getApplicationContext(), "External Storage Not Writable", Toast.LENGTH_LONG).show();

}

});

readB.setOnClickListener(new View.OnClickListener(){

@Override

public void onClick(View v) {

File file = new File(Environment.getExternalStorageDirectory().getAbsolutePath()+"/storagefile/testfile.txt");

if(file != null && file.exists()){

try {

FileInputStream fis = new FileInputStream(file);

String str = "";

int data;

while((data = fis.read()) != -1){

str += (char)data;

}

dataAndInfoTV.setText(str);

} catch (FileNotFoundException e) {

Toast.makeText(getApplicationContext(), "File not found", Toast.LENGTH_LONG).show();

} catch (IOException e) {

Toast.makeText(getApplicationContext(), "Error while reading File", Toast.LENGTH_LONG).show();

}

} else {

Toast.makeText(getApplicationContext(), "File does not exists", Toast.LENGTH_LONG).show();

}

});

//Getting permission for Marshmallow or higher version at runtime

getExternalStorageWritePermission();

}

/* Checks if external storage is available for read and write */

private boolean isExternalStorageWritable() {

String state = Environment.getExternalStorageState();

if (Environment.MEDIA_MOUNTED.equals(state)) {

return true;

}

return false;

}

private void getExternalStorageWritePermission(){

if (Build.VERSION.SDK_INT >= Build.VERSION_CODES.M) {

if(checkSelfPermission(Manifest.permission.WRITE_EXTERNAL_STORAGE) != PackageManager.PERMISSION_GRANTED){

// Should we show an explanation?

if (shouldShowRequestPermissionRationale(Manifest.permission.WRITE_EXTERNAL_STORAGE)) {

} else {

//Requesting permission.

ActivityCompat.requestPermissions(this, new String[]{Manifest.permission.WRITE_EXTERNAL_STORAGE}, 1);

}

@Override //Override from ActivityCompat.OnRequestPermissionsResultCallback Interface

public void onRequestPermissionsResult(int requestCode, String[] permissions, int[] grantResults) {

switch (requestCode) {

case 1: {

// If request is cancelled, the result arrays are empty.

if (grantResults.length > 0 && grantResults[0] == PackageManager.PERMISSION_GRANTED) {

// permission granted

}

return;

}

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Thanks

AndroidManifest.xml

activity_main.xml

MainActivity.java

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