The49.Maui.BottomSheet

NOTE: Coming from Gerald Versluis' video? Make sure to check the section on what changed since the video was made

What is Maui.BottomSheet?

Maui.BottomSheet is a .NET MAUI library used to display pages as Bottom Sheets.

Android	iOS

Setup

Enable this plugin by calling UseBottomSheet() in your MauiProgram.cs

using Maui.Insets;

public static class MauiProgram
{
	public static MauiApp CreateMauiApp()
	{
		var builder = MauiApp.CreateBuilder();
		
		// Initialise the plugin
		builder
                    .UseMauiApp<App>()
                    .UseBottomSheet();

		// the rest of your logic...
	}
}

XAML usage

In order to make use of the plugin within XAML you can use this namespace:

xmlns:the49="https://schemas.the49.com/dotnet/2023/maui"

Quick usage

Simply create a ContentView. Replace the extended class with BottomSheet in code-behind and in XAML:

using The49.Maui.BottomSheet;

public class MySheet : BottomSheet
{
    public MySheetPage()
    {
        InitializeComponent();
    }
}

<the49:BottomSheet xmlns="http://schemas.microsoft.com/dotnet/2021/maui"
             xmlns:x="http://schemas.microsoft.com/winfx/2009/xaml"
             xmlns:the49="https://schemas.the49.com/dotnet/2023/maui"
             x:Class="MyApp.MySheet"
             Title="MySheet">
            <!-- ... -->
</the49:BottomSheet>

The sheet can be opened by calling the ShowAsync() method of the page. It can be closed using DismissAsync():

const sheet = new MySheet();

// Show the sheet
sheet.ShowAsync();

// Alternatively, pass the window in which the sheet should show. Usually accessible from any other page of the app.
sheet.ShowAsync(Window);

// Call to programatically close the sheet
sheet.DismissAsync();

An extra parameter can be passed to both ShowAsync and DismissAsync to enable/disable the animations.

On Android, make sure your application's theme extends the Material3 theme. This mean you need a Platforms/Android/Resources/values/styles.xml file with the following content:

<?xml version="1.0" encoding="utf-8" ?>
<resources>
	<style name="Maui.MainTheme" parent="Theme.Material3.DayNight"></style>
</resources>

If you already have this file, just make sure the Maui.MainTheme style inherits the Theme.Material3.DayNight parent.

API

This library offers a BottomSheet, an extension of the ContentView with extra functionality

Properties

The following properties are available to use:

Name	Type	Default value	Description	Android	iOS
HasBackdrop	bool	false	Displays the sheet as modal. This has no effect on whether or not the sheet can be dismissed using gestures.	✅	✅*
HasHandle	bool	false	If true, display a drag handle at the top of the sheet	✅	✅
HandleColor	Color	null	Sets the color of the sheet's handle is HasHandle is true	✅	❌**
CornerRadius	double	-1	Sets the sheet's corner radius	✅***	✅
IsCancelable	bool	true	If false, prevents the dismissal of the sheet with user gestures	✅	✅
Detents	DetentsCollection	new DetentsCollection() { new ContentDetent() })	A collection of detents where the sheet will snap to when dragged. (See the Detents section for more info)	✅	✅
SelectedDetent	Detent	null	A two way property defining which detent is currently selected. Changes as the user slides, and updates the sheet's position when changed	✅	✅*

* iOS doesn't support the property largestUndimmedDetentIdentifier or selectedDetentIdentifer for custom detents as of right now. Se iOS documentation for largestUndimmedDetentIdentifier and selectedDetentIdentifer Only when the FullscreenDetent and/or MediumDetent are used those properties will work.

** iOS doesn't give any access to the grabber view

*** On Android, setting a custom corner radius will prevent the radius animation when the sheet hits the top of the screen

Detents:

Detents are snap point at which the sheet will stop when a drag gesture is released See iOS definition.

On Android only 3 detents are supported (See implemenation section for more info).

On iOS, detents are only fully supported for iOS 16 and up. On iOS 15, medium and large detents are used instead See iOS documentation.

Available detents

Name	Parameter	Description
FullscreenDetent		Full height of the screen
ContentDetent		Calculates the height of the page's content
AnchorDetent	Anchor	Anchor expects a View and will set its height to the Y position of that view. This is used to peek some content, then reveal more when the sheet is dragged up
HeightDetent	Height	Use a dp value to specify the detent height
RatioDetent	Ratio	Use a ratio of the full screen height
MediumDetent		A detent at the halfway point of the screen

Example:

<the49:BottomSheet xmlns="http://schemas.microsoft.com/dotnet/2021/maui"
             xmlns:x="http://schemas.microsoft.com/winfx/2009/xaml"
             xmlns:the49="https://schemas.the49.com/dotnet/2023/maui"
             x:Class="MyApp.SheetPage"
             Title="SheetPage">
    <the49:BottomSheet.Detents>
        <!-- Stop at the height of the screen -->
        <the49:FullscreenDetent />
        <!-- Stop at the height of the page content -->
        <the49:ContentDetent />
        <!-- Stop at 120dp -->
        <the49:HeightDetent Height="120" />
        <!-- Stop at 45% of the screen height -->
        <the49:RatioDetent Ratio="0.45" />
        <!-- Stop at the height of the divider view -->
        <the49:AnchorDetent Anchor="{x:Reference divider}" />
    </the49:BottomSheet.Detents>
    <VerticalStackLayout Spacing="16">
        <VerticalStackLayout>
            <!-- some content -->
        </VerticalStackLayout>
        <BoxView x:Name="divider" />
        <VerticalStackLayout>
            <!-- more content -->
        </VerticalStackLayout>
    </VerticalStackLayout>
</the49:BottomSheetPage>

Custom detent

You can create a custom detent by extending the default Detent class and implementing its GetHeight abstract method

Events

The following events are available to use:

Name	EventArg	Description	Android	iOS
Dismissed	DismissOrigin	Invoked when the sheet is dismissed. The EventArgs will either be DismissOrigin.Gesture when the user dragged it down or DismissOrigin.Programmatic when Dismiss is called.	✅	✅
Showing	EventArg.Emtpy	Called when the sheet is about to animate in. This is the best time to configure the behavior of the sheet for specific platforms (See Platform specifics)	✅	✅
Shown	EventArg.Emtpy	Called when the sheet finished animating in.	✅	✅

Platform specifics

On Android, the Google.Android.Material.BottomSheet.BottomSheetBehavior is made available under sheet.Controller.Behavior, to ensure the property is set, access it when the Showing event is fired. Learn more about it here: BottomSheetBehavior  |  Android Developers

On iOS, the UIKit.UISheetPresentationController is made available under sheet.Controller.SheetPresentationController, to ensure the property is set, access it when the Showing event is fired. Learn more about it here: UISheetPresentationController | Apple Developer Documentation

Common questions

How can I remove the backdrop on iOS

A sheet without backdrop works on iOS only if using MediumDetent and FullscreenDetent. Using the OnPlatform tool replace the detent on iOS to only use those and it will work.

Note: In the future, iOS might allow custom detents to support the largestUndimmableDetentIdentifier. If that happens, this plugin will be updated to support it

Here is how you can use the detents you need on Android, and use the detents compatible with HasBackdrop and SelectedDetent:

A IsDefault property can be used to select the detent that will be shown when calling ShowAsync. Otherwise the smallest detent is used.

<the49:BottomSheet xmlns="http://schemas.microsoft.com/dotnet/2021/maui"
             xmlns:x="http://schemas.microsoft.com/winfx/2009/xaml"
             xmlns:the49="https://schemas.the49.com/dotnet/2023/maui"
             x:Class="MyApp.SheetPage"
             Title="SheetPage">
    <the49:BottomSheet.Detents>
        <OnPlatform>
            <On Platform="Android">
                <the49:FullscreenDetent />
                <the49:ContentDetent />
                <the49:AnchorDetent Anchor="{x:Reference divider}" />
            </On>
            <On Platform="iOS">
                <the49:FullscreenDetent />
                <the49:MediumDetent />
            </On>
        </OnPlatform>
    </the49:BottomSheet.Detents>
    <VerticalStackLayout Spacing="16">
        <VerticalStackLayout>
            <!-- some content -->
        </VerticalStackLayout>
        <BoxView x:Name="divider" />
        <VerticalStackLayout>
            <!-- more content -->
        </VerticalStackLayout>
    </VerticalStackLayout>
</the49:BottomSheetPage>

How do I prevent the rounded corner to animate on Android?

var sheet = new MySheet();
sheet.Showing += (s, e) =>
{
    page.Controller.Behavior.DisableShapeAnimations();
};
sheet.ShowAsync(Window);

How can I change the detent used when showing the sheet

You can either add IsDefault="True" to the detent or set SelectedDetent to one of your detents before calling ShowAsync.

How do I change the corner radius?

Use the CornerRadius property.

Implementation details

iOS

The bottom sheet on iOS is presented using the UIViewController's PresentViewController and configuring the sheet with UISheetPresentationController.

Detents are created using the custom method

Android

The Material library's bottom sheet is used.

A xml layout contains a Frame, CoordinatorLayout and another Frame with the com.google.android.material.bottomsheet.BottomSheetBehavior behavior. The layout is inflated and added to the DrawerLayout is using AppShell or CoordinatorLayout is using NavigationPage

A backdrop is added and animated when requested

Detents are created using a combination of expandedOffset, halfExpandedRatio and peekHeight. These are the only configurable stop points for the bottom sheets, and that is why this library only supports up to 3 detents on Android.

Changes since Gerald Versluis' video

If you're coming from Gerald Versluis' video, a few things have changed. Here is what you need to know:

• Property names have been updated to be more consistent, discoverable and aligned with standard MAUI properties:

  • ShowHandle is now HasHandle
  • Cancelable is now IsCancelable
  • IsModal is now HasBackdrop

• 2 new properties have been added:

  • HandleColor
  • SelectedDetent

• Methods have been renamed

  • Show is now ShowAsync and completes when the animation of the sheet finishes. It also accepts a boolean to turn off animations
  • Dismiss is now DismissAsync and completes when the animation of the sheet finishes. It also accepts a boolean to turn off animations

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Made within The49