MainActivity.kt
package com.example.jetpack
import android.os.Bundle
import android.text.Editable
import android.text.TextWatcher
import androidx.appcompat.app.AppCompatActivity
import kotlinx.android.synthetic.main.activity_main.*
import java.util.regex.Pattern
class MainActivity : AppCompatActivity() {
override fun onCreate(savedInstanceState: Bundle?) {
super.onCreate(savedInstanceState)
setContentView(R.layout.activity_main)
// show password rules in text view
textView.text = "Password minimum length 8"
textView.append("\n1 uppercase")
textView.append("\n1 number")
textView.append("\n1 special character")
// add text changed listener for edit text
editText.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) {
s?.apply {
// check user input a valid formatted password
if (isValidPassword() && toString().length>=8) {
editText.error == null
}else{
// show error on input invalid password
editText.error = "invalid password."
}
}
}
override fun afterTextChanged(s: Editable?) {
}
})
}
}
// extension function to validate password rules/patterns
fun CharSequence.isValidPassword(): Boolean {
val passwordPattern = "^(?=.*[0-9])(?=.*[A-Z])(?=.*[@#$%^&+=!])(?=\\S+$).{4,}$"
val pattern = Pattern.compile(passwordPattern)
val matcher = pattern.matcher(this)
return matcher.matches()
}
activity_main.xml
<?xml version="1.0" encoding="utf-8"?>
<androidx.constraintlayout.widget.ConstraintLayout
xmlns:android="http://schemas.android.com/apk/res/android"
xmlns:app="http://schemas.android.com/apk/res-auto"
xmlns:tools="http://schemas.android.com/tools"
android:id="@+id/constraintLayout"
android:layout_width="match_parent"
android:layout_height="match_parent"
android:background="#FEFEFA"
tools:context=".MainActivity">
<EditText
android:id="@+id/editText"
android:layout_width="0dp"
android:layout_height="wrap_content"
android:layout_marginStart="12dp"
android:layout_marginEnd="12dp"
android:padding="12dp"
android:textSize="30sp"
android:inputType="textPassword"
android:fontFamily="sans-serif-condensed-medium"
app:layout_constraintBottom_toBottomOf="parent"
app:layout_constraintEnd_toEndOf="parent"
app:layout_constraintStart_toStartOf="parent"
app:layout_constraintTop_toTopOf="parent"
app:layout_constraintVertical_bias="0.12" />
<TextView
android:id="@+id/textView"
android:layout_width="0dp"
android:layout_height="wrap_content"
android:layout_marginTop="12dp"
android:fontFamily="sans-serif-condensed-medium"
android:gravity="center"
android:padding="8dp"
android:textColor="#4F42B5"
android:textSize="22sp"
app:layout_constraintEnd_toEndOf="parent"
app:layout_constraintStart_toStartOf="parent"
app:layout_constraintTop_toBottomOf="@+id/editText"
tools:text="TextView" />
</androidx.constraintlayout.widget.ConstraintLayout>
