'Kotlin-Android First App Unresolved Reference TextView Button etc

I'm new to Android & Kotlin development.

I wanted to get started with a simple "Hello World", but am already running into problems.

I added a Textview to my MainActivity and want to set an onClick listener to change the text of a TextView I dragged into the activity.

The compiler is now complaining that 'TextView' is an unresolved reference (it does the same with Buttons etc.).

I then added a kotlinx import as suggested by a website, but this fails to solve anything. Code sample below, anything with an asterisk as a line comment was added by me.

package com.example.my.mynewapp

import android.support.v7.app.AppCompatActivity
import android.os.Bundle
import kotlinx.android.synthetic.main.fragmentX.view.* // *

class MainActivity : AppCompatActivity() {

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

        val textView: TextView = findViewById(R.id.testView) as TextView  // *
        textView.setOnClickListener { // *
            textView.text = "You clicked me! You flipping clicked me!" // *
        } // *

    }
}

Would anyone have any idea what's going on?

Solution 1:^[1]

It should have been automatically imported, but there should be

import android.widget.<WhateverIsMissing>

Replace WhateverIsMissing with the reference that is unresolved

Solution 2:^[2]

if you use Android Studio v.4.2.1 you have to add this line in (build.gradle) file like this:-

id 'kotlin-android-extensions'

Solution 3:^[3]

You are inflating activity_main.xml in your class.
Does this TextView belong to the above layout?
If it does then you don't need findViewById()
Just add to your imports:

import kotlinx.android.synthetic.main.activity_main.*

and not:

import kotlinx.android.synthetic.main.fragmentX.view.*

then use testView (this is the id of the TextView unless it's a typo) anywhere in your activity class.

Solution 4:^[4]

One more thing to check if your imports seem complete:

In case you have defined more than one layout for your activity, fragment, etc. make sure that classes of corresponding controls match across layouts. This is the most common situation where I see this error message.

Solution 5:^[5]

When you add a new view (in this case TextView), the IDE will default its id to textView. The IDE will increment the id every time you add a new view of the same kind (textView2, textView3, and so on) even when you already deleted the previous views. For example:

// Capture the layout's TextView and set the string as its text
val textView = findViewById<TextView>(R.id.textView).apply {
    text = message
}

If you get Unresolved reference: textView from the R.id.textView, check the corresponding XML file. Specifically, the Component Tree:

To change the id, select the view and in the Attributes window, change the id:

Solution 6:^[6]

add apply plugin: 'kotlin-android-extensions' in the build.gradle by double shift to search and write "build" then add the plugin in the dependencies section then import option should appear for you

Solution 7:^[7]

Under the project folder there are gradle scripts
Open the build.gradle (module:your app name)
add 'id-android-extensions' into the plugins
then sync it

Sources

This article follows the attribution requirements of Stack Overflow and is licensed under CC BY-SA 3.0.

Source: Stack Overflow

Solution	Source
Solution 1	frogstair
Solution 2	Majid Hajibaba
Solution 3	forpas
Solution 4	jerry
Solution 5	M Imam Pratama
Solution 6	7ossam
Solution 7	MaxV

'Kotlin-Android First App Unresolved Reference TextView Button etc

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Solution 2:[2]

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