<!--permission for internet-->
<uses-permission android:name="android.permission.INTERNET"/>

<?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"
    tools:context=".MainActivity">

    <!--edit text to enter your input-->
    <EditText
        android:id="@+id/idEdtLanguage"
        android:layout_width="match_parent"
        android:layout_height="wrap_content"
        android:layout_centerHorizontal="true"
        android:layout_marginTop="50dp"
        android:hint="Enter your name"
        android:padding="4dp"
        android:textColor="@color/black"
        android:textSize="20sp" />

    <!--button to detect language of the input text-->
    <Button
        android:id="@+id/idBtnDetectLanguage"
        android:layout_width="wrap_content"
        android:layout_height="wrap_content"
        android:layout_below="@id/idTVDetectedLanguageCode"
        android:layout_centerInParent="true"
        android:text="Detect language" />

    <!--text view to display the code of entered text-->
    <TextView
        android:id="@+id/idTVDetectedLanguageCode"
        android:layout_width="match_parent"
        android:layout_height="wrap_content"
        android:layout_below="@id/idEdtLanguage"
        android:layout_centerHorizontal="true"
        android:layout_margin="20dp"
        android:gravity="center_horizontal"
        android:text="Language code"
        android:textAlignment="center"
        android:textSize="20sp" />

</RelativeLayout>

import android.os.Bundle;
import android.view.View;
import android.widget.Button;
import android.widget.EditText;
import android.widget.TextView;
import android.widget.Toast;

import androidx.annotation.NonNull;
import androidx.appcompat.app.AppCompatActivity;

import com.google.android.gms.tasks.OnFailureListener;
import com.google.android.gms.tasks.OnSuccessListener;
import com.google.firebase.ml.naturallanguage.FirebaseNaturalLanguage;
import com.google.firebase.ml.naturallanguage.languageid.FirebaseLanguageIdentification;

public class MainActivity extends AppCompatActivity {

    // creating variables for our image view,
    // text view and two buttons.
    private EditText edtLanguage;
    private TextView languageCodeTV;
    private Button detectLanguageBtn;

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

        // on below line we are initializing our variables.
        edtLanguage = findViewById(R.id.idEdtLanguage);
        languageCodeTV = findViewById(R.id.idTVDetectedLanguageCode);
        detectLanguageBtn = findViewById(R.id.idBtnDetectLanguage);

        // adding on click listener for button
        detectLanguageBtn.setOnClickListener(new View.OnClickListener() {
            @Override
            public void onClick(View v) {
                // getting string from our edit text.
                String edt_string = edtLanguage.getText().toString();
                // calling method to detect language.
                detectLanguage(edt_string);
            }
        });
    }

    private void detectLanguage(String string) {
        // initializing our firebase language detection.
        FirebaseLanguageIdentification languageIdentifier = FirebaseNaturalLanguage.getInstance().getLanguageIdentification();

        // adding method to detect language using identify language method.
        languageIdentifier.identifyLanguage(string).addOnSuccessListener(new OnSuccessListener<String>() {
            @Override
            public void onSuccess(String s) {
                // below line we are setting our
                // language code to our text view.
                languageCodeTV.setText(s);
            }
        }).addOnFailureListener(new OnFailureListener() {
            @Override
            public void onFailure(@NonNull Exception e) {
                // handling error method and displaying a toast message.
                Toast.makeText(MainActivity.this, "Fail to detect language : \n" + e, Toast.LENGTH_SHORT).show();
            }
        });
    }
}