Android资料设计 - LinearLayout提升

Question

I'm just starting with material design and having a problem getting elevation to work with anything but a CardView. Specifically, should it work on a LinearLayout?

<LinearLayout
            android:paddingTop="10dp"
            android:orientation="vertical"
            android:paddingLeft="@dimen/activity_horizontal_margin"
            android:paddingRight="@dimen/activity_horizontal_margin"
            android:layout_width="match_parent"
            android:layout_height="wrap_content"
            android:elevation="2dp">
            <LinearLayout
                android:id="@+id/shareLayout"
                android:layout_width="match_parent"
                android:layout_height="wrap_content"
                android:paddingBottom="10dp">

                <ImageView
                    android:id="@+id/shareIcon"
                    android:layout_width="wrap_content"
                    android:layout_height="wrap_content"
                    android:src="@drawable/ic_share_black_48dp"/>
                <TextView
                    android:id="@+id/shareText"
                    android:layout_width="wrap_content"
                    android:layout_height="wrap_content"
                    android:layout_gravity="center_vertical"
                    android:paddingLeft="10dp"
                    android:text="@string/action_share"/>
            </LinearLayout>
            <LinearLayout
                android:layout_width="wrap_content"
                android:layout_height="wrap_content">

                <ImageView
                    android:layout_width="wrap_content"
                    android:layout_height="wrap_content"
                    android:src="@drawable/ic_computer_black_48dp"/>
                <TextView
                    android:layout_width="wrap_content"
                    android:layout_height="wrap_content"
                    android:layout_gravity="center_vertical"
                    android:paddingLeft="10dp"
                    android:text="@string/action_desktop"/>
            </LinearLayout>

        </LinearLayout>

This code produces no visible elevation of the layout - no shadow. If I put it in a CardView, the elevation works, but then I have problems getting click events to fire. I have tried removing the images, but that has no effect. Do I just have to wrap everything I want elevated in a CardView, or is there another way? Thanks.

I am testing on a Nexus 7 running Android 5.0.2.

UPDATE

I tried the outline provider as suggested, and that results in a shadow, but a strange one.

It looks like the LinearLayout is angled or something instead of just elevated. Changing the margin doesn't seem to help. Anybody have any other ideas?

Answer 1

Shadows are generated for all views with ViewOutlineProvider. Such provider is generated automatically from view's background if a background is set. The shadow takes the shape and the transparency of the background. To make a transparent view cast a shadow, you have to set your own ViewOutlineProvider:

view.setOutlineProvider(new ViewOutlineProvider() {
    @Override
    public void getOutline(View view, Outline outline) {
        outline.setRect(0, 0, view.getWidth(), view.getHeight());
    }
});

Make sure that the shadow caster has enough space to draw its shadow. CardView adds its own padding for that purpose by default.