I found a very good solution here, I'm using it with kotlin.
First, in the drawable folder you have to create item_count.xml:
<?xml version="1.0" encoding="utf-8"?> <shape xmlns:android="http://schemas.android.com/apk/res/android"
android:shape="rectangle">
<corners android:radius="8dp" />
<solid android:color="#f20000" />
<stroke
android:width="2dip"
android:color="#FFF" />
<padding
android:bottom="5dp"
android:left="5dp"
android:right="5dp"
android:top="5dp" />
</shape>
In your Activity_Main Layout some like:
<RelativeLayout
android:id="@+id/badgeLayout"
android:layout_width="40dp"
android:layout_height="40dp"
android:layout_toRightOf="@+id/badge_layout1"
android:layout_gravity="end|center_vertical"
android:layout_marginEnd="5dp">
<RelativeLayout
android:id="@+id/relative_layout1"
android:layout_width="wrap_content"
android:layout_height="wrap_content">
<Button
android:id="@+id/btnBadge"
android:layout_width="match_parent"
android:layout_height="match_parent"
android:background="@mipmap/ic_notification" />
</RelativeLayout>
<TextView
android:id="@+id/txtBadge"
android:layout_width="18dp"
android:layout_height="18dp"
android:layout_alignRight="@id/relative_layout1"
android:background="@drawable/item_count"
android:text="22"
android:textColor="#FFF"
android:textSize="7sp"
android:textStyle="bold"
android:gravity="center"/>
</RelativeLayout>
And you can modify like:
btnBadge.setOnClickListener { view ->
Snackbar.make(view,"badge click", Snackbar.LENGTH_LONG) .setAction("Action", null).show()
txtBadge.text = "0"
}