Jetpack Compose Basics - Looking for an alternative to menus or dialogues? Try the Modal Bottom Sheet
Peter Šuly
Android developer
Bottom Sheet is component used as supplementary surface anchored to bottom of screen. This article will be about exact type of Bottom Sheet - Modal Bottom Sheet and how to use it in Jetpack Compose.
It's an alternative to menus or dialogs, it has to be dismissed (either by swipe or by some other user interaction) to interact with underlaying content of screen. In Jetpack Compose, bottom sheet is implemented via ModalBottomSheet composable.
ModalBottomSheet has 3 possible state defined through sheetState parameter of type ModalBottomSheetValue. Possible values are Hidden, Expanded or HalfExpanded. Default value in sheet state is Hidden, own state can be remembered like this
ModalBottomSheet, as usual in Jetpack Compose, has many parameters for customisation, two of them are mandatory.
Mandatory parameters
sheetContent - composable, containing content of bottom sheet
content - composable, containing content of screen behind the bottom sheet. This content is overlayed by scrimColor when bottom sheet is in Expanded state
Optional parameters
sheetState - controls state of ModalBottomSheet
modifier - used for changes from the caller side
sheetShape - shape of bottom sheet e.g. *RoundedCornerShape*(topStart = 24.*dp*, topEnd = 24.*dp*)
sheetElevation - elevation of bottom sheet in dp
sheetBackgroundColor - background color of bottom sheet, defaultly set to surface color
sheetContentColor - content color contrasting on background color, default value is computed using contentColorFor function
scrimColor - color of overlay applied on content when bottom sheet is visible
Behaviour of bottom sheet
How to open ModalBottomSheet on Button click?
There are show() and hide() functions ready for animated transition of ModalBottomSheet which can be called on modalBottomSheetState. These are suspend functions, because animation run as coroutine, scope or LaunchedEffect is needed to use them.
How to disable Half Expanded state in ModalBottomSheet?
In some cases, HalfExpanded state is not desirable and luckily there is a way to disable it by returning false in confirmStateChange lambda.
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