android kotlin - EditText input filter decimal

MainActivity.kt


package com.example.jetpack

import android.os.Bundle
import android.text.InputFilter
import android.text.Spanned
import android.widget.EditText
import androidx.appcompat.app.AppCompatActivity
import kotlinx.android.synthetic.main.activity_main.*
import java.util.regex.Matcher
import java.util.regex.Pattern
import java.util.regex.PatternSyntaxException


class MainActivity : AppCompatActivity() {
    override fun onCreate(savedInstanceState: Bundle?) {
        super.onCreate(savedInstanceState)
        setContentView(R.layout.activity_main)

        // apply edit text decimal input filter
        editText.inputFilterDecimal(
            // this values must be positive (0+) unless it throw exception
            maxDigitsIncludingPoint = 5,
            maxDecimalPlaces = 2
        )

        textView.text = "Max digits including point : 5"
        textView.append("\nMax decimal places : 2")
    }
}


// extension function to input filter edit text decimal digits
fun EditText.inputFilterDecimal(
    // maximum digits including point and without decimal places
    maxDigitsIncludingPoint: Int,
    maxDecimalPlaces: Int // maximum decimal places
){
    try {
        filters = arrayOf<InputFilter>(
            DecimalDigitsInputFilter(maxDigitsIncludingPoint, maxDecimalPlaces)
        )
    }catch (e: PatternSyntaxException){
        isEnabled = false
        hint = e.message
    }
}


// class to decimal digits input filter
class DecimalDigitsInputFilter(
    maxDigitsIncludingPoint: Int, maxDecimalPlaces: Int
) : InputFilter {
    private val pattern: Pattern = Pattern.compile(
        "[0-9]{0," + (maxDigitsIncludingPoint - 1) + "}+((\\.[0-9]{0,"
                + (maxDecimalPlaces - 1) + "})?)||(\\.)?"
    )

    override fun filter(
        p0: CharSequence?,p1: Int,p2: Int,p3: Spanned?,p4: Int,p5: Int
    ): CharSequence? {
        p3?.apply {
            val matcher: Matcher = pattern.matcher(p3)
            return if (!matcher.matches()) "" else null
        }
        return null
    }
}

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:inputType="numberDecimal"
        android:padding="12dp"
        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="25sp"
        app:layout_constraintEnd_toEndOf="parent"
        app:layout_constraintStart_toStartOf="parent"
        app:layout_constraintTop_toBottomOf="@+id/editText"
        tools:text="TextView" />

</androidx.constraintlayout.widget.ConstraintLayout>