How to read a simple text file in an Android App using Kotlin?

This example demonstrates how to read a simple text file in an Android App using Kotlin.

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"?>
<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:padding="8dp"
   tools:context=".MainActivity">
   <Button
      android:id="@+id/button"
      android:layout_width="match_parent"
      android:layout_height="wrap_content"
      android:layout_centerHorizontal="true"
      android:layout_marginTop="70dp"
      android:onClick="readTextFile"
      android:text="Read Text File" />
   <TextView
      android:layout_width="match_parent"
      android:layout_height="wrap_content"
      android:layout_marginTop="20dp"
      android:text="Read text File in Android"
      android:textAlignment="center"
      android:textColor="@android:color/background_dark"
      android:textSize="18sp"
      android:textStyle="bold" />
   <TextView
      android:id="@+id/textView"
      android:layout_width="match_parent"
      android:layout_height="wrap_content"
      android:layout_below="@id/button"
      android:layout_marginTop="10dp"
      android:textSize="20sp"
      android:textStyle="bold" />
</RelativeLayout>

Step 3 − Create a new Android Resource directory (raw.xml) and add a text file in the res/raw

Step 4 − Add the following code to src/MainActivity.kt

import android.os.Bundle
import android.view.View
import android.widget.TextView
import android.widget.Toast
import androidx.appcompat.app.AppCompatActivity
import java.io.BufferedReader
import java.io.IOException
import java.io.InputStream
import java.io.InputStreamReader
class MainActivity : AppCompatActivity() {
   lateinit var textView: TextView
   override fun onCreate(savedInstanceState: Bundle?) {
      super.onCreate(savedInstanceState)
      setContentView(R.layout.activity_main)
      title = "KotlinApp"
   }
   fun readTextFile(view: View) {
      var string: String? = ""
      val stringBuilder = StringBuilder()
      val `is`: InputStream = this.resources.openRawResource(R.raw.sample)
      val reader = BufferedReader(InputStreamReader(`is`))
      while (true) {
         try {
            if (reader.readLine().also { string = it } == null) break
         } catch (e: IOException) {
               e.printStackTrace()
         }
         stringBuilder.append(string).append("
")
         textView.text = stringBuilder
      }
      `is`.close()
      Toast.makeText(baseContext, stringBuilder.toString(),
      Toast.LENGTH_LONG).show()
   }
}

Step 5 − Add the following code to androidManifest.xml

<?xml version="1.0" encoding="utf-8"?>
<manifest xmlns:android="http://schemas.android.com/apk/res/android" package="app.com.q11">
   <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 the Run icon from the toolbar. Select your mobile device as an option and then check your mobile device which will display your default screen