Unable to set BottomSheetDialog initial height

Question

I'm trying to set a height peek from which the dialog must start, then the user if dragged should be able to expand it, the issue is that in any case the bottomsheet initial state get half of screen.

The BottomSheet looks like this:

<LinearLayout xmlns:android="http://schemas.android.com/apk/res/android"
    xmlns:tools="http://schemas.android.com/tools"
    xmlns:app="http://schemas.android.com/apk/res-auto"
    android:id="@+id/varianti_preferite_bottom_sheet"
    android:layout_width="match_parent"
    android:layout_height="match_parent"
    android:orientation="vertical"
    android:elevation="8dp"
    app:behavior_peekHeight="200dp"
    app:layout_behavior="com.google.android.material.bottomsheet.BottomSheetBehavior">

    <ImageButton
        android:id="@+id/closeButton"
        style="@style/Widget.AppCompat.ImageButton"
        android:minWidth="75dp"
        android:layout_width="wrap_content"
        android:layout_height="wrap_content"
        android:layout_gravity="center_horizontal"
        android:background="@drawable/bottom_border_radius"
        android:contentDescription="@string/bottom_sheet_close_button"
        android:padding="10dp"
        android:layout_marginBottom="16dp"
        app:srcCompat="@drawable/ic_baseline_close" />

    <androidx.recyclerview.widget.RecyclerView
        android:id="@+id/variantiRecycler"
        android:layout_width="match_parent"
        android:layout_height="match_parent"
        android:paddingBottom="16dp"
        android:clipToPadding="false"
        android:scrollbars="vertical"
        app:layoutManager="androidx.recyclerview.widget.GridLayoutManager"
        app:spanCount="4"
        tools:listitem="@layout/varianti_preferite">

    </androidx.recyclerview.widget.RecyclerView>


</LinearLayout>

What i've tried:

I've tried to override onCreateDialog and set HalfExpanded ratio manually but nothing changed:

   @NonNull
    @Override
    public Dialog onCreateDialog(@Nullable Bundle savedInstanceState) {
        BottomSheetDialog dialog = (BottomSheetDialog) super.onCreateDialog(savedInstanceState);

        dialog.setOnShowListener(dialog1 -> {
            BottomSheetDialog d = (BottomSheetDialog) dialog1;

            FrameLayout bottomSheet = (FrameLayout) d.findViewById(com.google.android.material.R.id.design_bottom_sheet);
            BottomSheetBehavior<FrameLayout> bottomSheetBehavior = BottomSheetBehavior.from(bottomSheet);
            bottomSheetBehavior.setHalfExpandedRatio(0.2f);
            bottomSheetBehavior.setFitToContents(false);

        });

        return dialog;
    }

Kotlin answers are welcome too.

Answer 1

The way that successfully works for me:

1. Add viewTreeObserver.addOnGlobalLayoutListener in onCreate to setup your BottomSheet behavior:

binding.root.viewTreeObserver.addOnGlobalLayoutListener {
    setupBottomSheetBehaviorForView(binding.bottomFragmentContainer)
}

2. Setup behavior:

private fun setupBottomSheetBehaviorForView(view: FragmentContainerView) {
    val behavior = BottomSheetBehavior.from(view)
    val screenHeight =
        if (Build.VERSION.SDK_INT >= Build.VERSION_CODES.R) {
            windowManager.currentWindowMetrics.bounds.height()
        } else {
            val metrics = DisplayMetrics()
            windowManager.defaultDisplay.getMetrics(metrics)
            metrics.heightPixels
        }

    val toolbarLocation = IntArray(COORDINATES_ARRAY_SIZE) // was added to avoid overlapping the toolbar
    binding.toolbar.getLocationOnScreen(toolbarLocation)   // with the bottom sheet (in case of full screen activity)

    behavior.apply {
        peekHeight = (screenHeight * BOTTOM_SHEET_PEEK_PERCENT).toInt()
        isFitToContents = false
        halfExpandedRatio = BOTTOM_SHEET_PEEK_PERCENT
        expandedOffset = toolbarLocation[1]  // it's optional
    }
}

where BOTTOM_SHEET_PEEK_PERCENT is Float const, for 40% initial peek height:

const val BOTTOM_SHEET_PEEK_PERCENT = 0.40f