Add badge to tab layout

badge.xml

<?xml version="1.0" encoding="utf-8"?>
<shape xmlns:android="http://schemas.android.com/apk/res/android"
    android:shape="rectangle">

    <solid android:color="#ea5444"/>
    <corners android:radius="12dp"/>

    <stroke
        android:width="0.5dp"
        android:color="#a6a0a0"/>
</shape>

BadgeTabLayout.kt

package es.cityride.mantapp

import android.content.Context
import android.graphics.PorterDuff
import android.graphics.drawable.Drawable
import android.support.design.widget.TabLayout
import android.util.AttributeSet
import android.util.SparseArray
import android.view.LayoutInflater
import android.view.View
import android.widget.ImageView
import android.widget.TextView
/**
 * Use:
 * tabLayout.with(tabPosition).badge(true).badgeCount(badgeCount).icon(R.drawable.ic_local_shipping_24dp).build()
 */

class BadgeTabLayout : TabLayout {
    private val mTabBuilders = SparseArray<Builder>()

    constructor(context: Context) : super(context) {}

    constructor(context: Context, attrs: AttributeSet) : super(context, attrs) {}

    constructor(context: Context, attrs: AttributeSet, defStyleAttr: Int) : super(context, attrs, defStyleAttr) {}

    fun with(position: Int): Builder {
        val tab = getTabAt(position)
        return with(tab)
    }

    /**
     * Apply a builder for this tab.
     *
     * @param tab for which we create a new builder or retrieve its builder if existed.
     * @return the required Builder.
     */
    fun with(tab: TabLayout.Tab?): Builder {
        if (tab == null) {
            throw IllegalArgumentException("Tab must not be null")
        }

        var builder: Builder? = mTabBuilders.get(tab.position)
        if (builder == null) {
            builder = Builder(this, tab)
            mTabBuilders.put(tab.position, builder)
        }

        return builder
    }

    class Builder
    /**
     * This construct take a TabLayout parent to have its context and other attributes sets. And
     * the tab whose icon will be updated.
     *
     * @param parent
     * @param tab
     */
    (parent: TabLayout, private val mTab: TabLayout.Tab) {

        private val mView: View?
        private val mContext: Context = parent.context
        private var mBadgeTextView: TextView? = null
        private var mIconView: ImageView? = null
        private var mIconDrawable: Drawable? = null
        private var mIconColorFilter: Int? = null
        private var mBadgeCount = Integer.MIN_VALUE
        private var mHasBadge = false

        init {
            // initialize current tab's custom view.
            if (mTab.customView != null) {
                this.mView = mTab.customView
            } else {
                this.mView = LayoutInflater.from(parent.context)
                        .inflate(R.layout.tab_custom_icon, parent, false)
            }

            if (mView != null) {
                this.mIconView = mView.findViewById<View>(R.id.tab_icon) as ImageView
                this.mBadgeTextView = mView.findViewById<View>(R.id.tab_badge) as TextView
            }

            if (this.mBadgeTextView != null) {
                this.mHasBadge = mBadgeTextView!!.visibility == View.VISIBLE
                try {
                    this.mBadgeCount = Integer.parseInt(mBadgeTextView!!.text.toString())
                } catch (er: NumberFormatException) {
                    er.printStackTrace()
                    this.mBadgeCount = INVALID_NUMBER
                }

            }

            if (this.mIconView != null) {
                mIconDrawable = mIconView!!.drawable
            }
        }


        fun imageContentDescription(contentDescription: String): Builder {
            mIconView?.contentDescription = contentDescription
            return this
        }

        /**
         * The related Tab is about to have a badge
         *
         * @return this builder
         */
        fun hasBadge(): Builder {
            mHasBadge = true
            return this
        }

        /**
         * The related Tab is not about to have a badge
         *
         * @return this builder
         */
        fun noBadge(): Builder {
            mHasBadge = false
            return this
        }

        /**
         * Dynamically set the availability of tab's badge
         *
         * @param hasBadge
         * @return this builder
         */
        // This method is used for DEBUG purpose only
        /*hide*/
        fun badge(hasBadge: Boolean): Builder {
            mHasBadge = hasBadge
            return this
        }

        /**
         * Set icon custom drawable by Resource ID;
         *
         * @param drawableRes
         * @return this builder
         */
        fun icon(drawableRes: Int): Builder {
            mIconDrawable = getDrawableCompat(mContext, drawableRes)
            return this
        }

        /**
         * Set icon custom drawable by Drawable Object
         *
         * @param drawable
         * @return this builder
         */
        fun icon(drawable: Drawable?): Builder {
            mIconDrawable = drawable
            return this
        }

        /**
         * Set drawable color. Use this when user wants to change drawable's color filter
         *
         * @param color
         * @return this builder
         */
        fun iconColor(color: Int?): Builder {
            mIconColorFilter = color
            return this
        }

        /**
         * increase current badge by 1
         *
         * @return this builder
         */
        fun increase(): Builder {
            mBadgeCount = if (mBadgeTextView == null)
                INVALID_NUMBER
            else
                Integer.parseInt(mBadgeTextView!!.text.toString()) + 1
            return this
        }

        /**
         * decrease current badge by 1
         *
         * @return
         */
        fun decrease(): Builder {
            mBadgeCount = if (mBadgeTextView == null)
                INVALID_NUMBER
            else
                Integer.parseInt(mBadgeTextView!!.text.toString()) - 1
            return this
        }

        /**
         * set badge count
         *
         * @param count expected badge number
         * @return this builder
         */
       public fun badgeCount(count: Int): Builder {
            mBadgeCount = count
            return this
        }

        /**
         * Build the current Tab icon's custom view
         */
        fun build() {
            if (mView == null) {
                return
            }

            // update badge counter
            if (mBadgeTextView != null) {
                mBadgeTextView!!.text = formatBadgeNumber(mBadgeCount)

                if (mHasBadge) {
                    mBadgeTextView!!.visibility = View.VISIBLE
                } else {
                    // set to View#INVISIBLE to not screw up the layout
                    mBadgeTextView!!.visibility = View.INVISIBLE
                }
            }

            // update icon drawable
            if (mIconView != null && mIconDrawable != null) {
                mIconView!!.setImageDrawable(mIconDrawable!!.mutate())
                // be careful if you modify this. make sure your result matches your expectation.
                if (mIconColorFilter != null) {
                    mIconDrawable!!.setColorFilter(mIconColorFilter!!, PorterDuff.Mode.MULTIPLY)
                }
            }

            mTab.customView = mView
        }

        companion object {

            /**
             * This badge widget must not support this value.
             */
            private val INVALID_NUMBER = Integer.MIN_VALUE
        }
    }

    companion object {

        private fun getDrawableCompat(context: Context, drawableRes: Int): Drawable? {
            var drawable: Drawable? = null
            try {
                    drawable = context.resources.getDrawable(drawableRes, context.theme)
            } catch (ex: NullPointerException) {
                ex.printStackTrace()
            }

            return drawable
        }

        /**
         * This format must follow User's badge policy.
         *
         * @param value of current badge
         * @return corresponding badge number. TextView need to be passed by a String/CharSequence
         */
        private fun formatBadgeNumber(value: Int): String {
            if (value < 0) {
                return "-" + formatBadgeNumber(-value)
            }

            return if (value <= 10) {
                // equivalent to String#valueOf(int);
                Integer.toString(value)
            } else "10+"

            // my own policy
        }
    }
}

tab_custom_icon

<?xml version="1.0" encoding="utf-8"?>
<FrameLayout
    xmlns:android="http://schemas.android.com/apk/res/android"
    android:layout_width="@dimen/actionbar_height"
    android:layout_height="@dimen/actionbar_height"
    android:background="@android:color/transparent"
    android:gravity="center"
    android:paddingBottom="4dp"
    android:paddingLeft="12dp"
    android:paddingRight="12dp"
    android:paddingTop="4dp">

    <ImageView
        android:id="@+id/tab_icon"
        android:layout_width="match_parent"
        android:layout_height="match_parent"
        android:layout_gravity="center"
        android:adjustViewBounds="true"
        android:background="@android:color/transparent"/>

    <TextView
        android:id="@+id/tab_badge"
        android:layout_width="wrap_content"
        android:layout_height="wrap_content"
        android:layout_gravity="top|end"
        android:layout_marginTop="4dp"
        android:background="@drawable/badge"
        android:paddingBottom="1dp"
        android:paddingLeft="6dp"
        android:paddingRight="6dp"
        android:paddingTop="1dp"
        android:textAppearance="@style/TextAppearance.AppCompat.Small"
        android:textColor="@android:color/white"
        android:textSize="12dp"/>
</FrameLayout>