Noti Badge Count View

attrs.xml

<?xml version="1.0" encoding="utf-8"?>
<resources>
    <declare-styleable name="NotiBadgeCountView">
        <attr name="count" format="integer" />
        <attr name="backgroundColor" format="color" />
    </declare-styleable>
</resources>

NotiBadgeCountView.kt

package com.example.androidplayground

import android.content.Context
import android.content.res.Resources
import android.graphics.Color
import android.graphics.drawable.Drawable
import android.graphics.drawable.GradientDrawable
import android.graphics.drawable.ShapeDrawable
import android.graphics.drawable.shapes.RoundRectShape
import android.util.AttributeSet
import android.view.Gravity
import androidx.appcompat.widget.AppCompatTextView

class NotiBadgeCountView @JvmOverloads constructor(
    context: Context, attrs:
    AttributeSet? = null,
    defStyleAttr: Int = 0
) : AppCompatTextView(context, attrs, defStyleAttr) {

    private var _count: Int = 0

    private var _backgroundColor: Int = DEFAULT_BACKGROUND_COLOR

    init {
        val a = context.obtainStyledAttributes(
            attrs, R.styleable.NotiBadgeCountView, 0, 0
        )
        a.getInt(R.styleable.NotiBadgeCountView_count, 0).let { count ->
            _count = count
            setCount(count)
        }

        _backgroundColor =
            a.getColor(R.styleable.NotiBadgeCountView_backgroundColor,
                DEFAULT_BACKGROUND_COLOR
            )
        updateBackground()

        gravity = Gravity.CENTER

        a.recycle()
    }

    fun setCount(count: Int) {
        _count = count
        text = if (!isLengthTooLong()) count.toString() else "${LIMIT}+"
        updateBackground()
    }

    private fun isLengthTooLong(): Boolean {
        return _count > LIMIT
    }

    private fun updateBackground() {
        background = if (isLengthTooLong()) {
            createRectangleBackground()
        } else {
            createCircleBackground()
        }
    }

    private fun createCircleBackground(): Drawable {
        val drawable = GradientDrawable()
        drawable.shape = GradientDrawable.OVAL
        drawable.setSize(dpToPx(24), dpToPx(24))
        drawable.setColor(_backgroundColor)
        return drawable
    }

    private fun createRectangleBackground(): Drawable {
        val cornerRadius = dpToPx(4).toFloat()
        val rectShape = RoundRectShape(
            floatArrayOf(
                cornerRadius,
                cornerRadius,
                cornerRadius,
                cornerRadius,
                cornerRadius,
                cornerRadius,
                cornerRadius,
                cornerRadius
            ), null, null
        )

        val drawable = ShapeDrawable(rectShape)
        drawable.paint.color = _backgroundColor
        drawable.intrinsicHeight = dpToPx(24)
        drawable.intrinsicWidth = dpToPx(36)
        drawable.setPadding(dpToPx(8), 0, dpToPx(8), 0)

        return drawable
    }

    companion object {
        private val DEFAULT_BACKGROUND_COLOR: Int = Color.parseColor("#ff0000")
        private const val LIMIT = 99
    }
}

fun dpToPx(dp: Int): Int {
    return (dp * Resources.getSystem().displayMetrics.density).toInt()
}

sample_activity.xml

<com.example.androidplayground.NotiBadgeCountView
    android:layout_width="wrap_content"
    android:layout_height="wrap_content"
    app:count="7" />

<com.example.androidplayground.NotiBadgeCountView
   android:layout_width="wrap_content"
   android:layout_height="wrap_content"
   app:backgroundColor="@color/colorAccent"
   app:count="100" />

screenshot

https://github.com/toe-lie/public-images/blob/master/NotiBadgeCountView-screenshot.png?raw=true