How to set error on EditText using DataBinding Framework MVVM

Question

I am using Android Data Binding framework I have suppose an EditText for login form with username as below

Answer 1

You can also add validation on edit text like this.

Layout file

BindingUtils

object BindingUtils {
        @BindingAdapter(value = ["error", "rule", "android:watcher"], requireAll = true)
        @JvmStatic
        fun watcher(textInputLayout: com.google.android.material.textfield.TextInputLayout, errorMsg: String, rule: ValidationRule, watcher: TextWatcher) {
            textInputLayout.editText?.addTextChangedListener(object : TextWatcher {
                override fun afterTextChanged(p0: Editable?) {
                }

                override fun beforeTextChanged(p0: CharSequence?, p1: Int, p2: Int, p3: Int) {
                }

                override fun onTextChanged(p0: CharSequence?, p1: Int, p2: Int, p3: Int) {
                    textInputLayout.error = null
                    if (rule == ValidationRule.EMPTY && !ValidationUtils.isValidEmail(p0.toString())) textInputLayout.error = errorMsg
                    if (rule == ValidationRule.PASSWORD && !ValidationUtils.isValidPassword(p0.toString())) textInputLayout.error = errorMsg
                }
            })
        }
    }

ValidationRule

enum class ValidationRule{
    EMPTY, EMAIL, PASSWORD
}

Don't forget to set the watcher in fragment or activity like this

binding.watcher = object : TextWatcher {
        override fun afterTextChanged(p0: Editable?) {
        }

        override fun beforeTextChanged(p0: CharSequence?, p1: Int, p2: Int, p3: Int) {
        }

        override fun onTextChanged(p0: CharSequence?, p1: Int, p2: Int, p3: Int) {
        }
    }