// add following permission in AndroidManifest.xml
<uses-permission android:name="android.permission.CALL_PHONE"/>

<?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=".MainActivity"
    android:padding="16dp">

    <RelativeLayout
        android:layout_width="match_parent"
        android:layout_height="wrap_content"
        android:layout_centerInParent="true">

        <EditText
            android:id="@+id/mobile"
            android:layout_width="match_parent"
            android:layout_height="wrap_content"
            android:hint="Enter your mobile number"
            android:inputType="phone"
            android:textColor="#000000"
            android:layout_marginTop="20dp"
            android:layout_marginBottom="6dp"/>

        <Button
            android:id="@+id/call"
            android:layout_width="wrap_content"
            android:layout_height="wrap_content"
            android:layout_below="@id/mobile"
            android:layout_centerInParent="true"
            android:text="Click to Call"
            android:textColor="#FFFFFF"
            android:padding="16dp"
            android:layout_marginTop="20dp"
            android:background="@color/colorPrimaryDark"/>
    </RelativeLayout>
</RelativeLayout>

                                    
                                  

                                    
                                        import android.Manifest;
import android.content.Intent;
import android.content.pm.PackageManager;
import android.net.Uri;
import android.os.Bundle;
import android.view.View;
import android.widget.Button;
import android.widget.EditText;
import android.widget.Toast;

import androidx.appcompat.app.AppCompatActivity;
import androidx.core.app.ActivityCompat;

public class MainActivity extends AppCompatActivity {

    EditText eMobile;
    Button bCall;
    String mobileNumber;

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

        eMobile = findViewById(R.id.mobile);
        bCall = findViewById(R.id.call);

        bCall.setOnClickListener(new View.OnClickListener() {
            @Override
            public void onClick(View v) {
                Intent intent = new Intent(Intent.ACTION_CALL);
                mobileNumber = eMobile.getText().toString();

                if(mobileNumber.equals("")) {
                    Toast.makeText(getApplicationContext(), "Please fill the fields", Toast.LENGTH_SHORT).show();
                } else {
                    intent.setData(Uri.parse("tel:" + mobileNumber));

                    if (ActivityCompat.checkSelfPermission(getApplicationContext(), Manifest.permission.CALL_PHONE) != PackageManager.PERMISSION_GRANTED) {
                        Toast.makeText(getApplicationContext(), "Permission not granted.", Toast.LENGTH_SHORT).show();
                        ActivityCompat.requestPermissions(MainActivity.this, new String[]{Manifest.permission.CALL_PHONE}, 1);
                    } else {
                        startActivity(intent);
                    }
                }
            }
        });
    }
}
                                    
                                  

                                      
                                        import android.Manifest
import android.content.Intent
import android.content.pm.PackageManager
import android.net.Uri
import android.os.Bundle
import android.view.View
import android.widget.Button
import android.widget.EditText
import android.widget.Toast
import androidx.appcompat.app.AppCompatActivity
import androidx.core.app.ActivityCompat

class MainActivity : AppCompatActivity() {

    private lateinit var eMobile: EditText
    private lateinit var bCall: Button
    private lateinit var mobileNumber: String

    companion object {
        private const val CALL_PERMISSION_REQUEST_CODE = 1
    }

    override fun onCreate(savedInstanceState: Bundle?) {
        super.onCreate(savedInstanceState)
        setContentView(R.layout.activity_main)

        eMobile = findViewById(R.id.mobile)
        bCall = findViewById(R.id.call)

        bCall.setOnClickListener {
            val intent = Intent(Intent.ACTION_CALL)
            mobileNumber = eMobile.text.toString()

            if (mobileNumber.isEmpty()) {
                Toast.makeText(applicationContext, "Please fill the fields", Toast.LENGTH_SHORT).show()
            } else {
                intent.data = Uri.parse("tel:$mobileNumber")

                if (ActivityCompat.checkSelfPermission(
                        applicationContext,
                        Manifest.permission.CALL_PHONE
                    ) != PackageManager.PERMISSION_GRANTED
                ) {
                    Toast.makeText(applicationContext, "Permission not granted.", Toast.LENGTH_SHORT).show()
                    ActivityCompat.requestPermissions(
                        this@MainActivity,
                        arrayOf(Manifest.permission.CALL_PHONE),
                        CALL_PERMISSION_REQUEST_CODE
                    )
                } else {
                    startActivity(intent)
                }
            }
        }
    }
}