Android Studio 4.1 Kotlin widget-ID not recognized in AminActivity.kt - android-studio

Question

I try to create a new project in Android Studio (AS) 4.1 with Kotlin. I use "empty activity" and create project "MyTest" .
AS creates activity_main.xml with unnamed TextView "Hello World". I give the id the name myText.
<?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">
<TextView
android:id="#+id/myText"
android:layout_width="wrap_content"
android:layout_height="wrap_content"
android:text="Hello World!"
app:layout_constraintBottom_toBottomOf="parent"
app:layout_constraintLeft_toLeftOf="parent"
app:layout_constraintRight_toRightOf="parent"
app:layout_constraintTop_toTopOf="parent" />
</androidx.constraintlayout.widget.ConstraintLayout>
The created MainActivity.kt is standard and looks like this
package com.example.mytest
import androidx.appcompat.app.AppCompatActivity
import android.os.Bundle
class MainActivity : AppCompatActivity() {
override fun onCreate(savedInstanceState: Bundle?) {
super.onCreate(savedInstanceState)
setContentView(R.layout.activity_main)
}
}
All this is normal AS, BUT
now in MAinActivity.kt it should be possible to type
myText = "any string"
but here myText is not recognised. And I don't understand that.
I have some small test-projects from earlier AS version. They look identical - and it works to type myText and myText is immediatly recognized.
What is wrong with my coding or project creation! Having created several projects and compared with former projects, I see no fault with my doing. Who has an idea?

Answer 1

You need to integrate Kotlin Android Extensions in your project in order to you have your views recognized like that. Just add the following lines in your build.gradle:
apply plugin: 'com.android.application'
apply plugin: 'kotlin-android'
apply plugin: 'kotlin-android-extensions'
More info in this article: https://antonioleiva.com/kotlin-android-extensions/
BUT
synthetic will be deprecated in Kotlin 1.4.20, https://youtrack.jetbrains.com/issue/KT-42121 due to not being null-safe. If you are going to maintain the project you are building for a awhile it will be batter not to use Kotlin Android Extensions.
Suggested alternatives in the link above are:
ViewBinding
FindViewById
Kotterknife (deprecated)
AndroidAnnotations
FindViewById is the 'official' method and it's easy to use, Kotlin suggests ViewBinding which has some boilerplate as I read (I haven't used it yet).

Answer 2

just add these lines in your build.gradle (app) at the top:
plugins {
id 'com.android.application'
id 'kotlin-android'
id 'kotlin-android-extensions' }
after that include this import statements in your MainActivity.kt file:
import kotlinx.android.synthetic.main.activity_main.*
for more clear info visit
`https://youtrack.jetbrains.com/issue/KT-42121`
After that don't forget to sync your gradle file..

Answer 3

As "kotlin-android-extensions" is deprecated now it's better to use view binding.
For this first enable view binding in build.gradle file by writing these line of codes under android block.
buildFeatures {
viewBinding true
}
then in activity file to use view binding features
first declare a global variable for binding as
private lateinit var binding: ActivityHomeBinding
Here ActivityHomeBinding is a auto generated class
then write these codes in OnCreate() method
binding = ActivityHomeBinding.inflate(layoutInflater)
setContentView(binding.root)