Preview:
<resources>
    <string name="app_name">Implicit Intent Example</string>
    <string name="phone_number">Phone Number</string>
    <string name="call">Call</string>
    <string name="call_logs">Call Logs</string>
    <string name="contact">Contact</string>
    <string name="web_browser">Web Browser</string>
    <string name="gallery">Gallery</string>
    <string name="camera">Camera</string>
    <string name="alarm">Alarm</string>
</resources>

----
<?xml version="1.0" encoding="utf-8"?>
<android.support.constraint.ConstraintLayout 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:isScrollContainer="true">

    <EditText
        android:id="@+id/et_number"
        android:layout_width="0dp"
        android:layout_height="wrap_content"
        android:layout_marginEnd="8dp"
        android:layout_marginLeft="8dp"
        android:layout_marginRight="8dp"
        android:layout_marginStart="8dp"
        android:layout_marginTop="8dp"
        android:ems="10"
        android:hint="@string/phone_number"
        android:inputType="number"
        app:layout_constraintEnd_toEndOf="parent"
        app:layout_constraintStart_toStartOf="parent"
        app:layout_constraintTop_toTopOf="parent" />

    <Button
        android:id="@+id/btn_call"
        android:layout_width="0dp"
        android:layout_height="wrap_content"
        android:layout_marginEnd="8dp"
        android:layout_marginLeft="8dp"
        android:layout_marginRight="8dp"
        android:layout_marginStart="8dp"
        android:layout_marginTop="8dp"
        android:text="@string/call"
        app:layout_constraintEnd_toEndOf="parent"
        app:layout_constraintStart_toStartOf="parent"
        app:layout_constraintTop_toBottomOf="@+id/et_number" />

    <Button
        android:id="@+id/btn_call_log"
        android:layout_width="0dp"
        android:layout_height="wrap_content"
        android:layout_marginEnd="8dp"
        android:layout_marginLeft="8dp"
        android:layout_marginRight="8dp"
        android:layout_marginStart="8dp"
        android:layout_marginTop="8dp"
        android:text="@string/call_logs"
        app:layout_constraintEnd_toEndOf="parent"
        app:layout_constraintStart_toStartOf="parent"
        app:layout_constraintTop_toBottomOf="@+id/btn_call" />

    <Button
        android:id="@+id/btn_contact"
        android:layout_width="0dp"
        android:layout_height="wrap_content"
        android:layout_marginEnd="8dp"
        android:layout_marginLeft="8dp"
        android:layout_marginRight="8dp"
        android:layout_marginStart="8dp"
        android:layout_marginTop="8dp"
        android:text="@string/contact"
        app:layout_constraintEnd_toEndOf="parent"
        app:layout_constraintStart_toStartOf="parent"
        app:layout_constraintTop_toBottomOf="@+id/btn_call_log" />

    <Button
        android:id="@+id/btn_browser"
        android:layout_width="0dp"
        android:layout_height="wrap_content"
        android:layout_marginEnd="8dp"
        android:layout_marginLeft="8dp"
        android:layout_marginRight="8dp"
        android:layout_marginStart="8dp"
        android:layout_marginTop="8dp"
        android:text="@string/web_browser"
        app:layout_constraintEnd_toEndOf="parent"
        app:layout_constraintStart_toStartOf="parent"
        app:layout_constraintTop_toBottomOf="@+id/btn_contact" />

    <Button
        android:id="@+id/btn_gallery"
        android:layout_width="0dp"
        android:layout_height="wrap_content"
        android:layout_marginEnd="8dp"
        android:layout_marginLeft="8dp"
        android:layout_marginRight="8dp"
        android:layout_marginStart="8dp"
        android:layout_marginTop="8dp"
        android:text="@string/gallery"
        app:layout_constraintEnd_toEndOf="parent"
        app:layout_constraintStart_toStartOf="parent"
        app:layout_constraintTop_toBottomOf="@+id/btn_browser" />

    <Button
        android:id="@+id/btn_camera"
        android:layout_width="0dp"
        android:layout_height="wrap_content"
        android:layout_marginEnd="8dp"
        android:layout_marginLeft="8dp"
        android:layout_marginRight="8dp"
        android:layout_marginStart="8dp"
        android:layout_marginTop="8dp"
        android:text="@string/camera"
        app:layout_constraintEnd_toEndOf="parent"
        app:layout_constraintStart_toStartOf="parent"
        app:layout_constraintTop_toBottomOf="@+id/btn_gallery" />

    <Button
        android:id="@+id/btn_alarm"
        android:layout_width="0dp"
        android:layout_height="wrap_content"
        android:layout_marginEnd="8dp"
        android:layout_marginLeft="8dp"
        android:layout_marginRight="8dp"
        android:layout_marginStart="8dp"
        android:layout_marginTop="8dp"
        android:text="@string/alarm"
        app:layout_constraintEnd_toEndOf="parent"
        app:layout_constraintStart_toStartOf="parent"
        app:layout_constraintTop_toBottomOf="@+id/btn_camera" />
</android.support.constraint.ConstraintLayout>

---
          import android.Manifest
import android.annotation.SuppressLint
import android.content.Intent
import android.content.pm.PackageManager
import android.net.Uri
import android.support.v7.app.AppCompatActivity
import android.os.Bundle
import android.provider.AlarmClock
import android.provider.CallLog
import android.provider.CallLog.*
import android.provider.ContactsContract
import android.provider.MediaStore
import android.support.v4.app.ActivityCompat
import android.support.v4.content.ContextCompat
import android.util.Log
import android.view.View
import kotlinx.android.synthetic.main.activity_main.*

class MainActivity : AppCompatActivity() {
    val CALL_REQUEST_CODE = 101

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

        setupPermissions()

        // Calling using intent
        btn_call.setOnClickListener(View.OnClickListener {
            val intent = Intent(Intent.ACTION_CALL)
            intent.data = Uri.parse("tel:" + et_number.getText())
            startActivity(intent)
        })

        // Call log
        btn_call_log.setOnClickListener(View.OnClickListener {
            val intent = Intent(Intent.ACTION_VIEW)
            intent.type = Calls.CONTENT_TYPE
            startActivity(intent)
        })

        //Contact
        btn_contact.setOnClickListener(View.OnClickListener {
            val intent = Intent(Intent.ACTION_PICK)
            intent.type = ContactsContract.Contacts.CONTENT_TYPE
            startActivity(intent)
        })

        // browser
        btn_browser.setOnClickListener(View.OnClickListener {
            val intent = Intent(Intent.ACTION_VIEW)
            intent.data = Uri.parse("https://tutorial.eyehunts.com/")
            startActivity(intent)
        })

        // Gallery
        btn_gallery.setOnClickListener(View.OnClickListener {
            val intent = Intent(Intent.ACTION_VIEW)
            intent.data = Uri.parse("content://media/external/images/media/")
            startActivity(intent)
        })

        // camera
        btn_camera.setOnClickListener(View.OnClickListener {
            val intent = Intent(MediaStore.ACTION_IMAGE_CAPTURE)
            startActivity(intent)
        })

        // alarm
        btn_alarm.setOnClickListener(View.OnClickListener {
            val intent = Intent(AlarmClock.ACTION_SHOW_ALARMS)
            startActivity(intent)
        })
    }

    private fun setupPermissions() {
        val permission = ContextCompat.checkSelfPermission(this,
                Manifest.permission.CALL_PHONE)

        if (permission != PackageManager.PERMISSION_GRANTED) {
            Log.i("noone", "Permission to Call has denied")
            makeRequest()
        }
    }

    private fun makeRequest() {
        ActivityCompat.requestPermissions(this,
                arrayOf(Manifest.permission.CALL_PHONE),
                CALL_REQUEST_CODE)
    }

}

----manfiest addition---
      <uses-permission android:name="android.permission.CALL_PHONE" />
        
        ----
      <manifest xmlns:android="http://schemas.android.com/apk/res/android"
    package="in.eyehunt.implicitintentexample">

    <uses-permission android:name="android.permission.CALL_PHONE" />
    <application <=Example

-------
      val emailIntent = Intent(Intent.ACTION_SENDTO).apply { 
    data = Uri.parse("mailto:abc@xyz.com")
}
startActivity(Intent.createChooser(emailIntent, "Send feedback"))

Email Intent
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