Android “elevation” not showing a shadow

Question

I have a ListView, and with each list item I want it to show a shadow beneath it. I am using Android Lollipop's new elevation feature to set a Z on the View that I want to cast a shadow, and am already doing this effectively with the ActionBar (technically a Toolbar in Lollipop). I am using Lollipop's elevation, but for some reason it isn't showing a shadow under the list items. Here is how each list item's layout is set up:

<?xml version="1.0" encoding="utf-8"?>
<RelativeLayout xmlns:android="http://schemas.android.com/apk/res/android"
    xmlns:app="http://schemas.android.com/apk/res-auto"
    android:orientation="vertical"
    style="@style/block"
    android:gravity="center"
    android:layout_gravity="center"
    android:background="@color/lightgray"
    >

    <RelativeLayout
        android:layout_width="300dp"
        android:layout_height="300dp"
        android:layout_marginLeft="40dp"
        android:layout_marginRight="40dp"
        android:layout_marginTop="20dp"
        android:layout_marginBottom="20dp"
        android:elevation="30dp"
        >

        <ImageView
            android:id="@+id/documentImageView"
            android:layout_width="match_parent"
            android:layout_height="match_parent"
            android:scaleType="centerCrop" />

        <LinearLayout
            android:orientation="vertical"
            android:layout_width="match_parent"
            android:layout_height="wrap_content"
            android:background="@color/alphared"
            android:layout_alignParentBottom="true" >

            <appuccino.simplyscan.Extra.CustomTextView
                android:id="@+id/documentName"
                android:layout_width="match_parent"
                android:layout_height="wrap_content"
                android:textColor="@color/white"
                app:typeface="light"
                android:paddingLeft="16dp"
                android:paddingTop="8dp"
                android:paddingBottom="4dp"
                android:singleLine="true"
                android:text="New Document"
                android:textSize="27sp"/>

            <appuccino.simplyscan.Extra.CustomTextView
                android:id="@+id/documentPageCount"
                android:layout_width="match_parent"
                android:layout_height="wrap_content"
                android:textColor="@color/white"
                app:typeface="italic"
                android:paddingLeft="16dp"
                android:layout_marginBottom="16dp"
                android:text="1 page"
                android:textSize="20sp"/>

        </LinearLayout>

    </RelativeLayout>

</RelativeLayout>

However, here is how it shows the list item, without a shadow:

I have also tried the following to no avail:

1. Set the elevation to the ImageView and TextViews themselves instead of the parent layout.
2. Applied a background to the ImageView.
3. Used TranslationZ in place of Elevation.

Answer 1

I had some luck with setting clipChildren="false" on the parent layout.

Answer 2

I've been playing around with shadows on Lollipop for a bit and this is what I've found:

1. It appears that a parent ViewGroup's bounds cutoff the shadow of its children for some reason; and
2. shadows set with android:elevation are cutoff by the View's bounds, not the bounds extended through the margin;
3. the right way to get a child view to show shadow is to set padding on the parent and set android:clipToPadding="false" on that parent.

Here's my suggestion to you based on what I know:

1. Set your top-level RelativeLayout to have padding equal to the margins you've set on the relative layout that you want to show shadow;
2. set android:clipToPadding="false" on the same RelativeLayout;
3. Remove the margin from the RelativeLayout that also has elevation set;
4. [EDIT] you may also need to set a non-transparent background color on the child layout that needs elevation.

At the end of the day, your top-level relative layout should look like this:

<RelativeLayout xmlns:android="http://schemas.android.com/apk/res/android"
    xmlns:app="http://schemas.android.com/apk/res-auto"
    style="@style/block"
    android:gravity="center"
    android:layout_gravity="center"
    android:background="@color/lightgray"
    android:paddingLeft="40dp"
    android:paddingRight="40dp"
    android:paddingTop="20dp"
    android:paddingBottom="20dp"
    android:clipToPadding="false"
    >

The interior relative layout should look like this:

<RelativeLayout
    android:layout_width="300dp"
    android:layout_height="300dp"
    android:background="[some non-transparent color]"
    android:elevation="30dp"
    >

Answer 3

Ugh, just spent an hour trying to figure this out. In my case I had a background set, however it was set to a color. This is not enough, you need to have the background of the view set to a drawable.

e.g. This won't have a shadow:

<LinearLayout
    android:layout_width="match_parent"
    android:layout_height="165dp"
    android:background="@color/ight_grey"
    android:elevation="20dp"
    android:orientation="vertical"
    />

but this will

<LinearLayout
    android:layout_width="match_parent"
    android:layout_height="165dp"
    android:background="@drawable/selector_grey"
    android:elevation="20dp"
    android:orientation="vertical"
    />

EDIT: Have also discovered that if you use a selector as a background, if you don't have the corner set then the shadow won't show up in the Preview window but it will show up on the device

e.g. This doesn't have a shadow in preview:

<selector xmlns:android="http://schemas.android.com/apk/res/android">
    <item>
        <shape android:shape="rectangle">
            <solid android:color="@color/white" />
            <stroke
                android:width="1dp"
                android:color="@color/grey"/>
        </shape>
    </item>
</selector>

but this does:

<selector xmlns:android="http://schemas.android.com/apk/res/android">
    <item>
        <shape android:shape="rectangle">
            <solid android:color="@color/white" />
            <corners android:radius="1dp" />
            <stroke
                android:width="1dp"
                android:color="@color/grey"/>
        </shape>
    </item>
</selector>

Answer 4

Adding background color helped me.

<CalendarView
    android:layout_width="match_parent"
    android:id="@+id/calendarView"
    android:layout_alignParentTop="true"
    android:layout_alignParentStart="true"
    android:layout_height="wrap_content"
    android:elevation="5dp"

    android:background="@color/windowBackground"

    />

Answer 5

I believe your issue stems from the fact that you have applied the elevation element to a relative layout that fills its parent. Its parent clips all child views within its own drawing canvas (and is the view that handles the child's shadow). You can fix this by applying an elevation property to the topmost RelativeLayout in your view xml (the root tag).

Answer 6

If you are adding elevation to a button element, you need to add the following line:

android:stateListAnimator="@null"

See Android 5.0 android:elevation Works for View, but not Button?