android - BottomSheetDialog with transparent background

Question

I would like to display a bottom sheet dialog less wide than the screen width.

For instance, the Share option from Google Play Music on a Nexus 9.

Do you know how to achieve this ?

For now I just succed to reduce the width of the sheet content but the background is still at the screen width and display a white background.

Some code:

build.gradle

compile 'com.android.support:design:23.3.0'

MainActivity

@Override
protected void onCreate(Bundle savedInstanceState) {
    ...

    mBottomSheetDialog = new BottomSheetDialog(this);
    mBottomSheetDialog.setContentView(R.layout.sheet_test);
    mBottomSheetDialog.setOnDismissListener(new DialogInterface.OnDismissListener() {
        @Override
        public void onDismiss(DialogInterface dialog) {
            mBottomSheetDialog = null;
        }
    });
    mBottomSheetDialog.show();
}

sheet_test

<?xml version="1.0" encoding="utf-8"?>
<android.support.v4.widget.NestedScrollView xmlns:android="http://schemas.android.com/apk/res/android"
    android:layout_width="100dp"
    android:layout_height="match_parent"
    android:orientation="vertical">

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

        <TextView
            style="@style/TextAppearance.AppCompat.Body1"
            android:layout_width="wrap_content"
            android:layout_height="wrap_content"
            android:layout_margin="16dp"
            android:text="Some Text"
            android:textColor="@color/colorPrimary" />

        <View
            android:layout_width="match_parent"
            android:layout_height="1dp"
            android:background="#ddd" />

        <TextView
            style="@style/TextAppearance.AppCompat.Body1"
            android:layout_width="match_parent"
            android:layout_height="match_parent"
            android:layout_margin="16dp"
            android:text="Some Text" />

        <View
            android:layout_width="match_parent"
            android:layout_height="1dp"
            android:background="#ddd" />

    </LinearLayout>

</android.support.v4.widget.NestedScrollView>

Answer 1

This worked for me when using BottomSheetDialogFragment:

public class CustomDialogFragment extends BottomSheetDialogFragment {

  @Override
  public void onCreate(@Nullable Bundle savedInstanceState) {
    super.onCreate(savedInstanceState);
    setStyle(BottomSheetDialogFragment.STYLE_NORMAL, R.style.CustomBottomSheetDialogTheme);
  }
  
  ...
}

Also add this to your styles.xml

<style name="CustomBottomSheetDialogTheme" parent="Theme.Design.Light.BottomSheetDialog">
    <item name="bottomSheetStyle">@style/CustomBottomSheetStyle</item>
</style>

<style name="CustomBottomSheetStyle" parent="Widget.Design.BottomSheet.Modal">
    <item name="android:background">@android:color/transparent</item>
</style>

Option 2:

override fun getTheme() = R.style.CustomBottomSheetDialogTheme