The Cardview widget is a UI component that presents text and image content in views that resemble cards. This guide explains how to use and customize CardView in Xamarin.Android applications while maintaining backward compatibility with earlier versions of Android.
Cardview widget, introduced in Android 5.0 (Lollipop), is a UI
component that presents text and image content in views that resemble
CardView is implemented as a
FrameLayout widget with rounded
corners and a shadow. Typically, a
CardView is used to present a
single row item in a
GridView view group. For example,
the following screen shot is an example of a travel reservation app
CardView-based travel destination cards in a
This guide explains how to add the
CardView package to your
Xamarin.Android project, how to add
CardView to your layout, and how
to customize the appearance of
CardView in your app. In addition,
this guide provides a detailed list of
CardView attributes that you
can change, including attributes to help you use
CardView on versions
of Android earlier than Android 5.0 Lollipop.
The following is required to use new Android 5.0 and later features
CardView) in Xamarin-based apps:
Xamarin.Android – Xamarin.Android 4.20 or later must be installed and configured with either Visual Studio or Visual Studio for Mac.
Android SDK – Android 5.0 (API 21) or later must be installed via the Android SDK Manager.
Java JDK 1.8 – JDK 1.7 can be used if you are specifically targeting API level 23 and earlier. JDK 1.8 is available from Oracle.
Your app must also include the
package. To add the
Xamarin.Android.Support.v7.CardView package in
Visual Studio for Mac:
Open your project, right-click Packages and select Add Packages.
In the Add Packages dialog, search for CardView.
Select Xamarin Support Library v7 CardView, then click Add Package.
To add the
Xamarin.Android.Support.v7.CardView package in Visual
Open your project, right-click the References node (in the Solution Explorer pane) and select Manage NuGet Packages....
When the Manage NuGet Packages dialog is displayed, enter CardView in the search box.
When Xamarin Support Library v7 CardView appears, click Install.
CardView resembles a white card with minimally rounded
corners and a slight shadow. The following example Main.axml layout
displays a single
CardView widget that contains a
<?xml version="1.0" encoding="utf-8"?> <LinearLayout xmlns:android="http://schemas.android.com/apk/res/android" android:orientation="vertical" android:layout_width="fill_parent" android:layout_height="fill_parent" android:gravity="center_horizontal" android:padding="5dp"> <android.support.v7.widget.CardView android:layout_width="fill_parent" android:layout_height="245dp" android:layout_gravity="center_horizontal"> <TextView android:text="Basic CardView" android:layout_marginTop="0dp" android:layout_width="match_parent" android:layout_height="match_parent" android:gravity="center" android:layout_centerVertical="true" android:layout_alignParentRight="true" android:layout_alignParentEnd="true" /> </android.support.v7.widget.CardView> </LinearLayout>
If you use this XML to replace the existing contents of Main.axml, be sure to comment out any code in MainActivity.cs that refers to resources in the previous XML.
This layout example creates a default
CardView with a single line of
text as shown in the following screen shot:
In this example, the app style is set to the light Material Theme
Theme.Material.Light) so that the
CardView shadows and edges are
easier to see. For more information about theming Android 5.0 apps, see
Material Theme. In
the next section, we'll learn how to customize
CardView for an
You can modify the basic
CardView attributes to customize the
appearance of the
CardView in your app. For example, the elevation of
CardView can be increased to cast a larger shadow (which makes
the card seem to float higher above the background). Also, the corner
radius can be increased to make the corners of the card more rounded.
In the next layout example, a customized
CardView is used to create a
simulation of a print photograph (a "snapshot"). An
added to the
CardView for displaying the image, and a
positioned below the
ImageView for displaying the title of the image.
In this example layout, the
CardView has the following
cardElevationis increased to 4dp to cast a larger shadow.
cardCornerRadiusis increased to 5dp to make the corners appear more rounded.
CardView is provided by the Android v7 support library, its
attributes are not available from the
android: namespace. Therefore,
you must define your own XML namespace and use that namespace as the
CardView attribute prefix. In the layout example below, we will use
this line to define a namespace called
You can call this namespace
card_view or even
myapp if you
choose (it's accessible only within the scope of this file). Whatever
you choose to call this namespace, you must use it to prefix the
CardView attribute that you want to modify. In this layout example,
cardview namespace is the prefix for
<?xml version="1.0" encoding="utf-8"?> <LinearLayout xmlns:android="http://schemas.android.com/apk/res/android" xmlns:cardview="http://schemas.android.com/apk/res-auto" android:orientation="vertical" android:layout_width="fill_parent" android:layout_height="fill_parent" android:gravity="center_horizontal" android:padding="5dp"> <android.support.v7.widget.CardView android:layout_width="fill_parent" android:layout_height="245dp" android:layout_gravity="center_horizontal" cardview:cardElevation="4dp" cardview:cardCornerRadius="5dp"> <LinearLayout android:layout_width="fill_parent" android:layout_height="240dp" android:orientation="vertical" android:padding="8dp"> <ImageView android:layout_width="fill_parent" android:layout_height="190dp" android:id="@+id/imageView" android:scaleType="centerCrop" /> <TextView android:layout_width="fill_parent" android:layout_height="wrap_content" android:textAppearance="?android:attr/textAppearanceMedium" android:textColor="#333333" android:text="Photo Title" android:id="@+id/textView" android:layout_gravity="center_horizontal" android:layout_marginLeft="5dp" /> </LinearLayout> </android.support.v7.widget.CardView> </LinearLayout>
When this layout example is used to display an image in a photo viewing
CardView has the appearance of a photo snapshot, as depicted
in the following screenshot:
This screenshot is taken from the
sample app, which uses a
RecyclerView widget to present a scrolling
CardView images for viewing photos. For more information
RecyclerView, see the
Notice that a
CardView can display more than one child view in its
content area. For example, in the above photo viewing app example,
the content area is comprised of a
ListView that contains an
ImageView and a
CardView instances are often
arranged vertically, you can also arrange them horizontally (see
Creating a Custom View Style
for an example screenshot).
CardView Layout Options
CardView layouts can be customized by setting one or more attributes
that affect its padding, elevation, corner radius, and background color:
Each attribute can also be changed dynamically by calling a
CardView method (for more information on
methods, see the
CardView class reference).
Note that these attributes (except for background
color) accept a dimension value, which is a decimal number followed by
the unit. For example,
11.5dp specifies 11.5 density-independent
CardView offers five padding attributes to position content within the
card. You can set them in your layout XML or you can call
analogous methods in your code:
The padding attributes are explained as follows:
contentPadding– Inner padding between the child views of the
CardViewand all edges of the card.
contentPaddingBottom– Inner padding between the child views of the
CardViewand the bottom edge of the card.
contentPaddingLeft– Inner padding between the child views of the
CardViewand the left edge of the card.
contentPaddingRight– Inner padding between the child views of the
CardViewand the right edge of the card.
contentPaddingTop– Inner padding between the child views of the
CardViewand the top edge of the card.
Content padding attributes are relative to the boundary of the content
area rather than to any given widget located within the content area.
For example, if
contentPadding were sufficiently increased in the photo
viewing app, the
CardView would crop both the image and the text shown
on the card.
CardView offers two elevation attributes to control its elevation and,
as a result, the size of its shadow:
The elevation attributes are explained as follows:
cardElevation– The elevation of the
CardView(represents its Z axis).
cardMaxElevation– The maximum value of the
Larger values of
cardElevation increase the shadow size to make
CardView seem to float higher above the background. The
cardElevation attribute also determines the drawing order of
overlapping views; that is, the
CardView will be drawn under
another overlapping view with a higher elevation setting and above
any overlapping views with a lower elevation setting.
cardMaxElevation setting is useful for when your app changes
elevation dynamically – it prevents the shadow from extending
past the limit that you define with this setting.
Corner Radius and Background Color
CardView offers attributes that you can use to control its
corner radius and its background color. These two properties allow
you change the overall style of the
These attributes are explained as follows:
cardCornerRadius– The corner radius of all corners of the
cardBackgroundColor– The background color of the
In this diagram,
cardCornerRadius is set to a more rounded 10dp and
cardBackgroundColor is set to
"#FFFFCC" (light yellow).
You can use
CardView on versions of Android earlier than Android 5.0
CardView is part of the Android v7 support library,
you can use
CardView with Android 2.1 (API level 7) and higher.
However, you must install the
as described in Requirements, above.
CardView exhibits slightly different behavior on devices before
Lollipop (API level 21):
CardViewuses a programmatic shadow implementation that adds additional padding.
CardViewdoes not clip child views that intersect with the
CardView's rounded corners.
To help in managing these compatibility differences,
provides several additional attributes that you can configure in your
cardPreventCornerOverlap– Set this attribute to
trueto add padding when your app is running on earlier Android versions (API level 20 and earlier). This setting prevents
CardViewcontent from intersecting with the
CardView's rounded corners.
cardUseCompatPadding– Set this attribute to
trueto add padding when your app is running in versions of Android at or greater than API level 21. If you want to use
CardViewon pre-Lollipop devices and have it look the same on Lollipop (or later), set this attribute to
true. When this attribute is enabled,
CardViewadds additional padding to draw shadows when it runs on pre-Lollipop devices. This helps to overcome the differences in padding that are introduced when pre-Lollipop programmatic shadow implementations are in effect.
For more information about maintaining compatibility with earlier versions of Android, see Maintaining Compatibility.
This guide introduced the new
CardView widget included in Android
5.0 (Lollipop). It demonstrated the default
CardView appearance and
explained how to customize
CardView by changing its elevation,
corner roundness, content padding, and background color. It listed the
CardView layout attributes (with reference diagrams), and explained
how to use
CardView on Android devices earlier than Android 5.0
Lollipop. For more information about
CardView, see the
CardView class reference.