How i can set Half Expanded state for my BottomSheet

Question

I have layout with bottom sheet.

<androidx.coordinatorlayout.widget.CoordinatorLayout xmlns:android="http://schemas.android.com/apk/res/android"
    xmlns:app="http://schemas.android.com/apk/res-auto"
    android:id="@+id/coordinator_layout"
    android:layout_width="match_parent"
    android:layout_height="match_parent">

    <com.google.android.material.appbar.AppBarLayout
        android:id="@+id/appbar"
        android:layout_width="match_parent"
        android:layout_height="wrap_content"
        android:theme="@style/ThemeOverlay.AppCompat.Dark.ActionBar">

        <com.google.android.material.appbar.CollapsingToolbarLayout
            android:id="@+id/collapsing_toolbar"
            android:layout_width="match_parent"
            android:layout_height="match_parent"
            app:contentScrim="@color/colorPrimary"
            app:layout_scrollFlags="scroll|exitUntilCollapsed" />
    </com.google.android.material.appbar.AppBarLayout>


    <include layout="@layout/content_main_weather_map" />

    <include layout="@layout/bottom_sheet" />

</androidx.coordinatorlayout.widget.CoordinatorLayout>

Bottom sheet layout

 <?xml version="1.0" encoding="utf-8"?>
    <androidx.core.widget.NestedScrollView xmlns:android="http://schemas.android.com/apk/res/android"
        xmlns:app="http://schemas.android.com/apk/res-auto"
        xmlns:tools="http://schemas.android.com/tools"
        android:id="@+id/bottom_sheet"
        android:layout_width="match_parent"
        android:layout_height="match_parent"
        android:background="@android:color/white"
        android:clipToPadding="true"
        app:behavior_peekHeight="80dp"
        app:layout_behavior="@string/bottom_sheet_behavior">

        <LinearLayout
            android:layout_width="match_parent"
            android:layout_height="match_parent"
            android:orientation="vertical">

            <androidx.recyclerview.widget.RecyclerView
                android:id="@+id/weather_recycler"
                android:layout_width="match_parent"
                android:layout_height="wrap_content"
                android:layout_marginTop="8dp"
                tools:listitem="@layout/item_weather" />

        </LinearLayout>


    </androidx.core.widget.NestedScrollView>

It is necessary for me that my bottom sheet opens first half, and after re-dragging it opens to full screen. How is it done in google maps app. But I have no idea how to do this.

Answer 1

It is better to use the framework with its full potential. As official documentation states for method setFitToContents :

Sets whether the height of the expanded sheet is determined by the height of its contents, or if it is expanded in two stages (half the height of the parent container, full height of parent container). Default value is true.

So all you need is set setFitToContent to false with:

behavior = BottomSheetBehavior.from(your_bottom_sheet_xml)
behavior.isFitToContents = false
behavior.halfExpandedRatio = 0.6f

With this 3-line-code the bottom sheet will expand till 60% of the screen at first, and afterwards it will fully expand to 100%.

Hope it helps!

Answer 2

Just set BottomSheetBehaivor state to BottomSheetBehavior.STATE_HALF_EXPANDED. Also if you need after full expanding let user again go back to half expanded mode, you need to set peek height to half of window height.

val bottomSheetBehavior = BottomSheetBehavior.from<NestedScrollView>(bottom_sheet)
val metrics = resources.displayMetrics
bottomSheetBehavior.peekHeight = metrics.heightPixels / 2
bottomSheetBehavior.state = BottomSheetBehavior.STATE_HALF_EXPANDED