How to read a txt file in external storage with runtime permission in android?

Android Mobile Development Apps/Applications

This example demonstrates How to read a txt file in external storage with runtime permission in android (we have already created a folder called text and sample txt file in external storage).

Step 1 − Create a new project in Android Studio, go to File ⇒ New Project and fill all required details to create a new project.

Step 2 − Add the following code to res/layout/activity_main.xml.

<?xml version = "1.0" encoding = "utf-8"?>
<LinearLayout 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"
   android:orientation = "vertical">
   <Button
      android:id = "@+id/read"
      android:text = "read"
      android:layout_width = "wrap_content"
      android:layout_height = "wrap_content" />
   <TextView
      android:id = "@+id/output"
      android:layout_width = "wrap_content"
      android:textSize = "25sp"
      android:layout_height = "wrap_content" />
</LinearLayout>

In the above code, we have taken textview and button. When user click on button, it will take data from external storage and append the data to text view.

Step 3 − Add the following code to src/MainActivity.java

package com.example.andy.myapplication;

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

import java.io.BufferedReader;
import java.io.File;
import java.io.FileOutputStream;
import java.io.FileReader;
import java.io.IOException;

public class MainActivity extends AppCompatActivity {
   private static final int PERMISSION_REQUEST_CODE = 100;
   Button read;
   TextView output;

   @Override
   protected void onCreate(Bundle savedInstanceState) {
      super.onCreate(savedInstanceState);
      setContentView(R.layout.activity_main);
      output = findViewById(R.id.output);
      read = findViewById(R.id.read);
      read.setOnClickListener(new View.OnClickListener() {
         @Override
         public void onClick(View v) {
            String state = Environment.getExternalStorageState();
            if (Environment.MEDIA_MOUNTED.equals(state)) {
               if (Build.VERSION.SDK_INT > = 23) {
                  if (checkPermission()) {
                     File sdcard = Environment.getExternalStorageDirectory();
                     File dir = new File(sdcard.getAbsolutePath() + "/text/");
                     if(dir.exists()) {
                        File file = new File(dir, "sample.txt");
                        FileOutputStream os = null;
                        StringBuilder text = new StringBuilder();
                        try {
                           BufferedReader br = new BufferedReader(new FileReader(file));
                           String line;
                           while ((line = br.readLine()) ! = null) {
                              text.append(line);
                              text.append('
');
                           }
                           br.close();
                        } catch (IOException e) {
                           //You'll need to add proper error handling here
                        }
                        output.setText(text);
                     }
                  } else {
                     requestPermission(); // Code for permission
                  }
               } else {
                  File sdcard = Environment.getExternalStorageDirectory();
                  File dir = new File(sdcard.getAbsolutePath() + "/text/");
                  if(dir.exists()) {
                     File file = new File(dir, "sample.txt");
                     FileOutputStream os = null;
                     StringBuilder text = new StringBuilder();
                     try {
                        BufferedReader br = new BufferedReader(new FileReader(file));
                        String line;
                        while ((line = br.readLine()) ! = null) {
                           text.append(line);
                           text.append('
');
                        }
                        br.close();
                     } catch (IOException e) {
                        //You'll need to add proper error handling here
                     }
                     output.setText(text);
                  }
               }
            }
         }
      });
   }

   private boolean checkPermission() {
      int result = ContextCompat.checkSelfPermission(MainActivity.this, android.Manifest.permission.READ_EXTERNAL_STORAGE);
      if (result = = PackageManager.PERMISSION_GRANTED) {
         return true;
      } else {
         return false;
      }
   }
   private void requestPermission() {
      if (ActivityCompat.shouldShowRequestPermissionRationale(MainActivity.this, android.Manifest.permission.READ_EXTERNAL_STORAGE)) {
         Toast.makeText(MainActivity.this, "Write External Storage permission allows us to read files. Please allow this permission in App Settings.", Toast.LENGTH_LONG).show();
      } else {
         ActivityCompat.requestPermissions(MainActivity.this, new String[]{android.Manifest.permission.READ_EXTERNAL_STORAGE}, PERMISSION_REQUEST_CODE);
      }
   }

   @Override
   public void onRequestPermissionsResult(int requestCode, String permissions[], int[] grantResults) {
      switch (requestCode) {
         case PERMISSION_REQUEST_CODE:
         if (grantResults.length > 0 && grantResults[0] = = PackageManager.PERMISSION_GRANTED) {
            Log.e("value", "Permission Granted, Now you can use local drive .");
         } else {
            Log.e("value", "Permission Denied, You cannot use local drive .");
         }
         break;
      }
   }
}

Step 4 − Add the following code to manifest.xml

<?xml version = "1.0" encoding = "utf-8"?>
<manifest xmlns:android = "http://schemas.android.com/apk/res/android"
   package = "com.example.andy.myapplication">
   <uses-permission android:name = "android.permission.WRITE_EXTERNAL_STORAGE"/>
   <uses-permission android:name = "android.permission.READ_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>

Let's try to run your application. I assume you have connected your actual Android Mobile device with your computer. To run the app from android studio, open one of your project's activity files and click Run icon from the toolbar. Select your mobile device as an option and then check your mobile device which will display your default screen −