Kotlin addTextChangeListener lambda?

Question

How do you build a lambda expression for the EditText addTextChangeListener in Kotlin? Below gives an error:

passwordEditText.addTextChangedListener { charSequence  ->
    try {
        password = charSequence.toString()
    } catch (error: Throwable) {
        raise(error)
    }
}

Answer 1

addTextChangedListener() takes a TextWatcher which is an interface with 3 methods. What you wrote would only work if TextWatcher had only 1 method. I'm going to guess the error you're getting relates to your lambda not implementing the other 2 methods. You have 2 options going forward.

1. Ditch the lambda and just use an anonymous inner class

    editText.addTextChangedListener(object : TextWatcher {
      override fun afterTextChanged(s: Editable?) {
      }
    
      override fun beforeTextChanged(s: CharSequence?, start: Int, count: Int, after: Int) {
      }
    
      override fun onTextChanged(s: CharSequence?, start: Int, before: Int, count: Int) {
      }
    })

2. Create an extension method so you can use a lambda expression:

    fun EditText.afterTextChanged(afterTextChanged: (String) -> Unit) {
        this.addTextChangedListener(object : TextWatcher {
          override fun beforeTextChanged(s: CharSequence?, start: Int, count: Int, after: Int) {
          }
    
          override fun onTextChanged(s: CharSequence?, start: Int, before: Int, count: Int) {
          }
    
          override fun afterTextChanged(editable: Editable?) {
            afterTextChanged.invoke(editable.toString())
          }
        })
    }

And then use the extension like so:

editText.afterTextChanged { doSomethingWithText(it) }