Rounded modal bottom sheet as seen in new Google products(Tasks, News, etc.), described in this article: https://medium.com/halcyon-mobile/implementing-googles-refreshed-modal-bottom-sheet-4e76cb5de65b

bg_bottom_sheet_dialog_fragment.xml

<!-- Drawable used for the bottom sheet dialog background -->
<?xml version="1.0" encoding="utf-8"?>
<shape xmlns:android="http://schemas.android.com/apk/res/android"
    android:shape="rectangle">
    <corners
        android:topLeftRadius="@dimen/bottom_sheet_corner_radius"
        android:topRightRadius="@dimen/bottom_sheet_corner_radius" />
    <padding android:top="@dimen/bottom_sheet_top_padding" />
    <solid android:color="@color/primary" />
</shape>

dimens.xml

<dimen name="bottom_sheet_corner_radius">16dp</dimen>
<dimen name="bottom_sheet_top_padding">8dp</dimen>

RoundedBottomSheetDialogFragment.kt

package com.your.package

import android.app.Dialog
import android.os.Bundle
import com.your.package.R
import com.google.android.material.bottomsheet.BottomSheetDialog
import com.google.android.material.bottomsheet.BottomSheetDialogFragment

/**
 * BottomSheetDialog fragment that uses a custom 
 * theme which sets a rounded background to the dialog 
 * and doesn't dim the navigation bar
 */
open class RoundedBottomSheetDialogFragment : BottomSheetDialogFragment() {

    override fun getTheme(): Int = R.style.BottomSheetDialogTheme

    override fun onCreateDialog(savedInstanceState: Bundle?): Dialog = BottomSheetDialog(requireContext(), theme)

}

styles-v21.xml

<!-- v21 styles, you can merge these two if your minSdkVersion is >= 21 -->
<resources>
  
    <style name="BottomSheetDialogTheme" parent="BaseBottomSheetDialog">
        <item name="android:statusBarColor">@android:color/transparent</item>
        <item name="android:navigationBarColor">@color/white</item>
    </style>
  
</resources>

styles.xml

<resources>
    
  <!-- set the rounded drawable as background to your bottom sheet -->
    <style name="BottomSheet" parent="@style/Widget.Design.BottomSheet.Modal">
        <item name="android:background">@drawable/bg_bottom_sheet_dialog_fragment</item>
    </style>

    <style name="BaseBottomSheetDialog" parent="@style/Theme.Design.Light.BottomSheetDialog">
        <item name="android:windowIsFloating">false</item>
        <item name="bottomSheetStyle">@style/BottomSheet</item>
    </style>

    <style name="BottomSheetDialogTheme" parent="BaseBottomSheetDialog" />
  
</resources>

Hey @cakfan! As I mentioned in my article, there's no reason to use this implementation with MaterialComponents since there is an easier solution using ShapeTheming.

add full source code! :(

Just like this with the new API

<!-- Stuff to make the bottom sheet with round top borders -->
<style name="BottomSheetShapeAppearance" parent="ShapeAppearance.MaterialComponents.LargeComponent">
    <item name="cornerFamily">rounded</item>
    <item name="cornerSizeTopLeft">12dp</item>
    <item name="cornerSizeTopRight">12dp</item>
</style>

<style name="BottomSheet" parent="@style/Widget.Design.BottomSheet.Modal">
    <item name="shapeAppearance">@style/BottomSheetShapeAppearance</item>
</style>

<style name="BaseBottomSheetMenu" parent="@style/Theme.Design.Light.BottomSheetDialog">
    <item name="android:windowIsFloating">false</item>
    <item name="bottomSheetStyle">@style/BottomSheet</item>
</style>

<style name="BottomSheetMenuTheme" parent="@style/BaseBottomSheetMenu" />

Change background opacity as you scroll the dialog:

open class RoundedBottomSheetDialogFragment : BottomSheetDialogFragment() {

    override fun getTheme(): Int = R.style.BottomSheetDialogTheme

    override fun onCreateDialog(savedInstanceState: Bundle?): Dialog {
        val dialog = BottomSheetDialog(requireContext(), theme)

        dialog.setOnShowListener {
            dialog.behavior.setBottomSheetCallback(object : BottomSheetBehavior.BottomSheetCallback() {
                override fun onStateChanged(bottomSheet: View, newState: Int) {
                    if (newState == BottomSheetBehavior.STATE_HIDDEN) {
                        dialog.dismiss()
                    }
                }

                override fun onSlide(bottomSheet: View, slideOffset: Float) {
                    if(!slideOffset.isNaN()) dialog.window?.setDimAmount(0.5f - ((slideOffset * -1)/2))
                }
            })
        }

        return dialog
    }
}

setBottomSheetCallback is now deprecated, you can use addBottomSheetCallback now

Hi there,
you guys can read this article and take advantage of a modern way to do this.

Hi there,
you guys can read this article and take advantage of a modern way to do this.

Hey! I appreciate your modern implementation recommendation, but if you read the article linked at the top of the gist you'll see that the solution you are proposing is referenced in the article as well since the article was written before the introduction of shapeAppearances from MaterialComponents.