public class InsetViewTransformer extends BaseViewTransformer {
    @Override
    public void transformView(float translation, float maxTranslation, float peekedTranslation, BottomSheetLayout parent, View view) {
        float progress = Math.min(translation / peekedTranslation, 1);
        float scale = (1 - progress) + progress * 0.9f;
        view.setScaleX(scale);
        view.setScaleY(scale);
        if (translation == 0 || translation == parent.getHeight()) {
            parent.setBackgroundColor(0);
            ensureLayer(view, View.LAYER_TYPE_NONE);
        } else {
            parent.setBackgroundColor(view.getResources().getColor(<whatever you want>));
            ensureLayer(view, View.LAYER_TYPE_HARDWARE);
        }
        float translationToTop = -(view.getHeight() * (1 - scale)) / 2;
        view.setTranslationY(translationToTop + progress * 20 * view.getContext().getResources().getDisplayMetrics().density);
    }
    private void ensureLayer(View view, int layerType) {
        if (view.getLayerType() != layerType) {
            view.setLayerType(layerType, null);
        }
    }
}

// In your view class, override this method
@Override
protected void onSizeChanged(int w, int h, int oldw, int oldh) {
    // Necessary for showing elevation on 5.0+
    if (Build.VERSION.SDK_INT >= Build.VERSION_CODES.LOLLIPOP) {
        setOutlineProvider(new Util.ShadowOutline(w, h));
    }
}
// ShadowOutline implementation
@TargetApi(21)
static class ShadowOutline extends ViewOutlineProvider {
    int width;
    int height;
    ShadowOutline(int width, int height) {
        this.width = width;
        this.height = height;
    }
    @Override
    public void getOutline(View view, Outline outline) {
        outline.setRect(0, 0, width, height);
    }
}