1.AppBar
Code:
.kt file code
package com.example.my_fragment
import androidx.appcompat.app.AppCompatActivity
import android.os.Bundle
import android.view.Menu
import android.view.MenuItem
import android.widget.Toast
import kotlinx.android.synthetic.main.activity_main.*
class MainActivity : AppCompatActivity() {
    override fun onCreate(savedInstanceState: Bundle?) {
        super.onCreate(savedInstanceState)
        setContentView(R.layout.activity_main)
        setSupportActionBar(mytoolbar)
    }
    override fun onCreateOptionsMenu(menu: Menu?): Boolean {
        super.onCreateOptionsMenu(menu)
        menuInflater.inflate(R.menu.mymenu,menu)
        return true
    }
    override fun onOptionsItemSelected(item: MenuItem): Boolean {
        if(item.itemId==R.id.one){
            Toast.makeText(this,"Folder is clicked",Toast.LENGTH_LONG).show()
        }
        if(item.itemId==R.id.two){
            Toast.makeText(this,"Search is clicked",Toast.LENGTH_LONG).show()
        }
        if(item.itemId==R.id.s1){
            Toast.makeText(this,"This is toast",Toast.LENGTH_LONG).show()
        }
        return super.onOptionsItemSelected(item)
    }
}
.xml file code
<?xml version="1.0" encoding="utf-8"?>
<androidx.constraintlayout.widget.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">
    <androidx.appcompat.widget.Toolbar
        android:id="@+id/mytoolbar"
        android:layout_width="match_parent"
        android:layout_height="?attr/actionBarSize"
        tools:ignore="MissingConstraints"
        android:theme="@style/Theme.AppCompat.DayNight.DarkActionBar"
        android:background="@color/teal_700"
        app:titleTextColor="@color/white"
        android:elevation="4dp"/>
</androidx.constraintlayout.widget.ConstraintLayout>
New .xml file code
<?xml version="1.0" encoding="utf-8"?>
<menu xmlns:android="http://schemas.android.com/apk/res/android"
    xmlns:app="http://schemas.android.com/apk/res-auto">
    <item android:id="@+id/one" android:title="folder" android:icon="@drawable/ic_baseline_folder_24" app:showAsAction="always"/>
    <item android:id="@+id/two" android:title="search" android:icon="@drawable/ic_baseline_search_24" app:showAsAction="always"/>
    <item android:id="@+id/main" android:title="Main Menu">
        <menu>
            <item android:id="@+id/s1" android:title="Toast"/>
            <item android:id="@+id/s2" android:title="Exit"/>
        </menu>
    </item>
</menu>



2.Fragments
Code:
package srm.it.fragmentdemo
import androidx.appcompat.app.AppCompatActivity
import android.os.Bundle
import kotlinx.android.synthetic.main.activity_main.*
class MainActivity : AppCompatActivity() {
    override fun onCreate(savedInstanceState: Bundle?) {
        super.onCreate(savedInstanceState)
        setContentView(R.layout.activity_main)

        var state=0
        button.setOnClickListener {
            if(state==0)   {
supportFragmentManager.beginTransaction().replace(R.id.fragmentContainerView,first()).commit()
                state=1
            }
            else
{  supportFragmentManager.beginTransaction().replace(R.id.fragmentContainerView,second()).commit()
                state=0
            } 
}  } }



3. UI Components
Code:
package sy.it.ui_component
import androidx.appcompat.app.AppCompatActivity
import android.os.Bundle
import android.widget.RadioButton
import android.widget.Toast
import androidx.appcompat.app.AlertDialog
import kotlinx.android.synthetic.main.activity_main.*

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

        button.setOnClickListener {
            var name=box1.text.toString()
            var email= box2.text.toString()
            var dob=box3.text.toString()
            var pass=box4.text.toString()
            var compass=box5.text.toString()

            if(pass!=compass){
                Toast.makeText(this,"Password does not match",Toast.LENGTH_SHORT).show()
 }

            var gen=radioGroup.checkedRadioButtonId
            var gs=if (gen == -1) {
                Toast.makeText(this, "Select gender", Toast.LENGTH_SHORT).show()
            }
            else {
                findViewById<RadioButton>(gen).text.toString()
            }

            var term=if(checkBox.isChecked){
                checkBox.text.toString()
            }else{
                Toast.makeText(this, "Please accept our terms and conditions", Toast.LENGTH_SHORT).show()
            }
            textView7.text = """
                $name
                $email
                $dob
                $pass
                $gs
                $term
                """.trimIndent() }}}

