Material-components-android: [BottomSheetDialogFragment] What's the recommended way to customize the behavior of a BottomSheetDialogFragment?

[renanferrari]

Let's say I want my bottom sheet to skip its collapsed state. If I used a BottomSheetBehavior I could just set skipCollapse to true. What's the recommended way to achieve that on a BottomSheetDialogFragment?

So far, I've been retrieving and modifying the BottomSheetDialogFragment's inner BottomSheetBehavior myself, like so:

override fun onViewCreated(view: View, savedInstanceState: Bundle?) {
        super.onViewCreated(view, savedInstanceState)

        dialog?.setOnShowListener { dialogInterface ->
            val sheetDialog = dialogInterface as? BottomSheetDialog

            val bottomSheet = sheetDialog?.findViewById<FrameLayout>(
                    com.google.android.material.R.id.design_bottom_sheet
            )

            bottomSheet?.let {
                val behavior = BottomSheetBehavior.from(it)
                behavior.skipCollapsed = true
                // any other behavior modification here
            }
        }
    }

However, this approach seems kind of _hackish_ to me. Is there any alternative or is this the recommended way to achieve what I want?

[AradiPatrik]

I think you can set it in xml using app:behavior_skipCollapsed="true"
Also in situations where such an xml attribute is not available, using BindingAdapters can help hide the "hackish" implementation details.
Here you can find the full list of xml attributes you can use to customize bottomsheet behavior: https://github.com/material-components/material-components-android/blob/master/lib/java/com/google/android/material/bottomsheet/res/values/attrs.xml

[renanferrari]

@AradiPatrik Thank you, but I don't believe your answer addresses the main point of my question.

My question was specific to BottomSheetDialogFragment, so XML attributes are unavailable. I'm also not looking for ways to "hide" the details of my implementation.

I just want to understand, from the perspective of the maintainers of this library, what's the recommended way to achieve what I need in the context I have described.

[SYtor]

I facing same problem, are behavior attrs cannot be configured via xml for BottomSheetDialogFragment?

[renanferrari]

@SYtor Nope, it uses the default ones and you can only access/change them programmatically, like shown in my original post.

[iRYO400]

I've found a convenient way to config bottom sheet behavior using styles.

1. Customize default BottomSheet by overriding it's attributes, for example in styles.xml

    <style name="Widget.MyApp.BottomSheet.Modal" parent="Widget.MaterialComponents.BottomSheet.Modal">
        <item name="behavior_skipCollapsed">true</item>
        <item name="behavior_fitToContents">true</item>
        <item name="behavior_peekHeight">1000dp</item> // yep, that helped to skip collapsed state at initial
        <item name="behavior_hideable">true</item>
    </style>

Go inside Widget.MaterialComponents.BottomSheet.Modal to see what settings you can modify.

1. Then create custom theme inherited from Theme.Design.BottomSheetDialog and set that you want to override bottom sheet's style with you own. Also can be placed in styles.xml

    <style name="Theme.MyApp.BottomSheetDialog" parent="Theme.Design.BottomSheetDialog">
        <item name="bottomSheetStyle">@style/Widget.MyApp.BottomSheet.Modal</item>
    </style>

1. And the last, define your new created theme for bottom sheet dialog in your Activity's theme or Application's theme, which placed in themes.xml(hope you follow Google's recommendations about packaging styles&themes)

<style name="Base.Theme.MyApp" parent="Base.Theme.Root">
    ... too many other things
    <item name="bottomSheetDialogTheme">@style/Theme.MyApp.BottomSheetDialog</item>
</style>

[iRYO400]

@SYtor @renanferrari checkout my previous comment

P.S. I'm using the latest stable version of MaterialDesign dependency
com.google.android.material:material:1.1.0

[xanscale]

@renanferrari inside onViewCreated i used that

val behavior: BottomSheetBehavior<*> = (dialog as BottomSheetDialog).behavior
behavior.halfExpandedRatio = 0.3f
behavior.state = BottomSheetBehavior.STATE_HALF_EXPANDED

i don't know if it is the correct way