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Any suggestion how to have an EditText that receiving user input around 9 letters (or digits) and after finish (e.g: click some button action or lost keyboard focus), it’ll update the letters inside that EditText. Following are the requirements:

Input: 123456789



enter image description here


Please confirm if this is what you want to achieve?

There’s EditText, you want that EditText able to add newline (multiline) for every 3 character (after a simple actions)

If yes, here’s an opinionated solutions that might solve the underlying problems:

kotlin playground examples

The above screenshot is written in here

For the EditText part, what we can think of at the moment:

See Core-KTX extensions from here

// YourActivity.kt
import androidx.core.widget.doAfterTextChanged
import kotlin.text.buildString // this import is optional. to identify its origin

override fun onCreate(...) {
    // assign your `editText` & `textView` variable with usual `findViewById` or using `ViewBinding` if your project already using it

    // Directly listen for user input in EditText
    editText?.doAfterTextChanged { userInput ->
       if (userInput.length == 3) textView?.text = "$userInputn"

    // Or you can use the below approach:
    textView.text = buildString {
         editText?.toString()?.forEachIndexed { index, letter -> 
                // index start from 0
                // index+1 = 0+1, so we can start from 1-index
                // check for the reminder of index/3 == 0
                // meaning we are appending the `n` (newline) to the text
                if ((index+1) % 3 == 0) append("n")

// your_activity.xml
   <EditText ... id="@id/editText" />
   // create below TextView as a result of user inputs
   <TextView ... id="@id/textView" />

A few lines in the above snippet code omitted for readability, and yes there’s a few code will compile-error as well, needs to adjust it accordingly