A Number Control Widget for android with custom validations, min and max value setters, custom xml attributes, and listeners

README.md

Add This is attrs.xml for xml properties to work

<?xml version="1.0" encoding="utf-8"?>
<resources>
    <declare-styleable name="NumberControl">
        <attr name="maxNumber" format="integer" />
        <attr name="minNumber" format="integer" />
    </declare-styleable>

</resources>

NumberControlWidget.kt

package com.rwsentosa.mobileapp.widgets

import android.content.Context
import android.util.AttributeSet
import android.view.View
import android.widget.FrameLayout
import android.widget.ImageView
import android.widget.TextView
import androidx.databinding.BindingAdapter
import com.rwsentosa.mobileapp.R
import kotlinx.coroutines.flow.MutableSharedFlow
import kotlinx.coroutines.flow.MutableStateFlow
import kotlin.math.max
import kotlin.math.min

class NumberControl : FrameLayout {

    constructor(context: Context) : this(context, null)
    constructor(context: Context, attributeSet: AttributeSet?) : this(context, attributeSet, 0)
    constructor(
        context: Context,
        attributeSet: AttributeSet?,
        defStyleAttr: Int
    ) : super(
        context, attributeSet, defStyleAttr
    ) {
        init(context, attributeSet)
    }

    constructor(
        context: Context,
        attributeSet: AttributeSet?,
        defStyleAttr: Int,
        defStyleRes: Int
    ) : super(context, attributeSet, defStyleAttr, defStyleRes) {
        init(context, attributeSet)
    }

    private var view: View? = null
    private lateinit var btnPlus: ImageView
    private lateinit var btnMinus: ImageView
    private lateinit var tvValue: TextView

    private var listener: ((value: Int) -> Unit)? = null
    private var validator: ((value: Int) -> Boolean) = { value ->
        true
    }
    private var onMaxReachedListener: (() -> Unit)? = null
    private var onMinReachedListener: (() -> Unit)? = null

    var value: Int = 0
        set(value) {
            if (validator.invoke(value)) {
                // Validator Success
                field = value
                valueFlow.tryEmit(value)
                showValue(value)
                listener?.invoke(value)
            }
            if (field >= maxValue) onMaxReachedListener?.invoke()
            if (field <= minValue) onMinReachedListener?.invoke()
        }

    var maxValue: Int = Integer.MAX_VALUE
    var minValue: Int = 0

    var valueFlow: MutableSharedFlow<Int> = MutableStateFlow(0)

    fun setValueListener(listener: (value: Int) -> Unit) {
        this.listener = listener
    }

    fun setValidator(validator: (value: Int) -> Boolean) {
        this.validator = validator
    }

    private fun init(context: Context, attrs: AttributeSet?) {
        view = inflate(context, R.layout.view_number_control, this)

        btnPlus = view!!.findViewById(R.id.btnPlus)
        btnMinus = view!!.findViewById(R.id.btnMinus)
        tvValue = view!!.findViewById(R.id.tvValue)

        value = 0
        attrs?.let {
            val typedArray = context.obtainStyledAttributes(it, R.styleable.NumberControl)
            maxValue = typedArray.getInt(R.styleable.NumberControl_maxNumber, Integer.MAX_VALUE)
            minValue = typedArray.getInt(R.styleable.NumberControl_minNumber, minValue)
            typedArray.recycle()
        }
        setupListeners()
    }

    private fun setupListeners() {
        btnPlus.setOnClickListener { plus() }
        btnMinus.setOnClickListener { minus() }
    }

    private fun plus() {
        value = min(maxValue, value.plus(1))
    }

    private fun minus() {
        value = max(minValue, value.minus(1))
    }

    private fun showValue(value: Int) {
        tvValue.text = value.toString()
    }
}

@BindingAdapter("numberControlValue")
fun setNumberControlValue(view: NumberControl, value: Int) {
    view.value = value
}