Line drop in text editing Android Studio

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

Output:

123 
456 
789

enter image description here

Answer

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:

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 -> 
                append(c)
                // 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
<LinearLayout 
   ...
   <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