material-components_material-components-ios/components/Cards/README.md

Cards

Cards contain content and actions about a single subject.

Using cards

Cards are implemented by MDCCard, which inherits from UIControl, and MDCCardCollectionCell, which inherits from UICollectionViewCell.

A card's state determines its visual styling.

When treated as a UIControl (MDCCard), it has a default styling (UIControlStateNormal), and a highlighted styling (UIControlStateHighlighted) when interacted with.

When treated as a UICollectionViewCell (MDCCardCollectionCell), it has a default styling (MDCCardCellStateNormal), a highlighted styling (MDCCardCellStateHighlighted), and lastly a selected styling (MDCCardCellStateSelected).

Customization to the card is exposed via its API either in MDCCard or MDCCardCollectionCell. Currently the card consists of these customizations:

• The border width for a specific state
• The border color for a specific state
• The shadow elevation for a specific state
• The shadow color for a specific state
• The corner radius for the card

(MDCCardCollectionCell customization only):

• Changing the image that appears in the Selected state.
• Changing the image tint color that appears in the Selected state.

An MDCCard can be added and used as you would add any UIView or UIControl, if manually in code, or through Interface Builder.

An MDCCardCollectionCell can be added, used, and reused as a UICollectionViewCell, if manually in code, or through Interface Builder.

Cards Classes

MDCCard

MDCCard subclasses UIControl and provides a simple class for developers to subclass and create custom cards with ink, shadows, corner radius, and stroke matching the Material spec.

MDCCard uses the highlighted property that is built-in in UIControl and the UIControlState to move between states.

MDCCardCollectionCell

MDCCardCollectionCell subclasses UICollectionViewCell and provides a simple collection view cell for developers to use in their collections with ink, shadows, corner radius, and stroke matching the Material spec.

MDCCardCollectionCell uses the selected property that is built-in in UICollectionViewCell and has its own MDCCardCellState to keep track of the current state it is in.

Install MDCCard or MDCCardCollectionCell

In order to use MDCCard or MDCCardCollectionCell, first add Cards to your Podfile:

pod MaterialComponents/Cards

Then, run the installer.

pod install

After that, import the Cards target.

Swift

import MaterialComponents.MaterialCards

Objective-C

#import "MaterialCards.h"

From there, either initialize an MDCCard like you would any UIView or use MDCCardCollectionCell as a superclass for a custom UICollectionViewCell.

Making cards accessible

To help ensure your cards are accessible to as many users as possible, please be sure to review the following recommendations:

Accessibility for Cards in a Collection

Since assistive technologies visit all cards in a collection in a sequential order, it is often easier to distinguish between elements that belong to different cards by aggregating all the card's information so the card is read as a single sentence.
This can be done by setting an appropriate accessibilityLabel for the card. Additionally, set the card's isAccessibilityElement to true. Cards are a container element and setting isAccessibiltyElement for a container turns off individually selecting its subelements.

Swift

card.isAccessibilityElement = true
card.accessibilityLabel = "Location \(userLocation.name) is popular with users " +
  "who enjoy \(userLocation.popularActivityMatchingUserProfile(userProfile))"

Objective-C

card.isAccessibilityElement = YES;
card.accessibilityLabel = [NSString 
  stringWithFormat:@"Location %@ is popular with users who enjoy %@",  
  userLocation.name, 
  userLocation.popularActivityMatchingUserProfile(userProfile)];

Accessibility for Single Cards

Nested elements in MDCCards are available to assistive technologies without additional customization, however additional setup may be needed to accommodate special scenarios, such as:

Accessibility for Single Cards: Images

Images that have additional context beyond text that is already presented on the card.
For example, news article images can benefit from an accessibilityLabel describing their content.

Swift

articleImageView.isAccessibilityElement = true
articleImageView.accessibilityLabel = "Event or scene description"

Objective-C

articleImageView.isAccessibilityElement = YES;
articleImageView.accessibilityLabel = @"Event or scene description";

Accessibility for Single Cards: Star Rating

Star or rating images should have an accessibilityLabel describing its purpuse and an accessibilityValue describing the rating value.

Swift

ratingView.isAccessibilityElement = true
ratingView.accessibilityLabel = "Average customer rating, out of " + 
  "\(MDCProductRating.maximumValue) stars"
ratingView.accessibilityValue = (String)product.averageRating

Objective-C

ratingView.isAccessibilityElement = YES;
ratingView.accessibilityLabel = [NSString stringWithFormat:@"Average customer" +
  " rating, out of %d stars", MDCProductRating.maximumValue];
ratingView.accessibilityValue = @(product.averageRating).stringValue;

Accessibility for Single Cards: Reordering elements

Primary content or actions that appear lower on the screen will be read last by assistive technologies, sometimes after longer or non-primary content. To change the order, or group elements together, you can make the card an accessibility container by adopting the UIAccessibilityContainer protocol. Grouping and order is controlled by creating as many UIAccessibilityElement elements as needed, and returning them in the desired order.

Card

Cards can be used to build custom UIs, like the one shown above, from CardWithImageViewAndButtonsExample.

MDCCard and MDCCardCollectionCell inherit from UIControl and UICollectionViewCell, respectively.

• MDCCard

  • GitHub source

• MDCCardCollectionCell

  • GitHub source

Card examples using MDCCard

MDCCard can be used like a regular UIView. This is an example of a regular card:

Swift

let card = MDCCard(frame: CGRect(x: 30, y: 100, width: 150, height: 150))
card.applyTheme(withScheme: containerScheme)
view.addSubview(card)

Objective-C

MDCCard *card = [[MDCCard alloc] initWithFrame:CGRectMake(30, 100, 150, 150)];
[card applyThemeWithScheme:containerScheme];
[view addSubview:card];

Card examples using MDCCardCollectionCell

MDCCardCollectionCell can be used like a regular UICollectionViewCell. This is an example of MDCCardCollectionCells in a collection:

Swift

collectionView.register(MDCCardCollectionCell.self, forCellWithReuseIdentifier: "Cell")

func collectionView(_ collectionView: UICollectionView,
                    cellForItemAt indexPath: IndexPath) -> UICollectionViewCell {
  let cell = collectionView.dequeueReusableCell(withReuseIdentifier: "Cell",
                                                for: indexPath) as! MDCCardCollectionCell
  // If you wanted to have the card show the selected state when tapped
  // then you need to turn isSelectable to true, otherwise the default is false.
  cell.isSelectable = true
  cell.cornerRadius = 8
  return cell
}

Objective-C

[self.collectionView registerClass:[MDCCardCollectionCell class]
        forCellWithReuseIdentifier:@"Cell"];

- (UICollectionViewCell *)collectionView:(UICollectionView *)collectionView
                  cellForItemAtIndexPath:(NSIndexPath *)indexPath {
  MDCCardCollectionCell *cell =
  [collectionView dequeueReusableCellWithReuseIdentifier:@"Cell"
                                            forIndexPath:indexPath];
  // If you wanted to have the card show the selected state when tapped
  // then you need to turn selectable to true, otherwise the default is false.
  [cell setSelectable:YES];
  [cell setCornerRadius:8];
  return cell;
}

Anatomy and key properties

A card has a container and an optional thumbnail, header text, secondary text, media, supporting text, buttons and icons.

1. Container
2. Thumbnail
3. Header text
4. Secondary text
5. Media
6. Supporting text
7. Buttons
8. Icons
9. Checked icon (not shown)

Note: All the optional elements of a card's content are implemented through the use of other views/components.

Container attributes for MDCCard

	Attribute	Related method(s)	Default value
Color	backgroundColor	-setBackgroundColor: backgroundColor:	Surface color
Foreground color	N/A	N/A	N/A
Stroke color	layer.borderColor	-setBorderColor:forState: -borderColorForState:	On surface color at 37% opacity
Stroke width	layer.borderWidth	-setBorderWidth:forState: -borderWidthForState:	1
Shape	shapeGenerator	-setShapeGenerator: -shapeGenerator	MDCRectangleShapeGenerator
Elevation	N/A	-setShadowElevation:forState: -shadowElevationForState:	1
Ripple color	rippleView.rippleColor	N/A	nil

Container attributes for MDCCardCollectionCell

	Attribute	Related method(s)	Default value
Color	backgroundColor	-setBackgroundColor: backgroundColor:	Surface color
Foreground color	N/A	N/A	N/A
Stroke color	layer.borderColor	-setBorderColor:forState: -borderColorForState:	On surface color at 37% opacity
Stroke width	layer.borderWidth	-setBorderWidth:forState: -borderWidthForState:	1
Shape	shapeGenerator	-setShapeGenerator: -shapeGenerator	MDCRectangleShapeGenerator
Elevation	N/A	-setShadowElevation:forState: -shadowElevationForState:	1
Ripple color	rippleView.rippleColor	N/A	nil

Theming cards

Cards supports Material Theming using a Container Scheme. MDCCard and MDCCardCollectionCell have both default and outlined theming methods. Learn more about theming extensions. Below is a screenshot of an MDCCard with the Material Design Shrine theme:

Cards theming example

To make use of Cards theming install the Cards theming extensions with Cocoapods. First, add the following line to your Podfile.

pod MaterialComponents/Cards+Theming

Then Run the installer.

pod install

Next, import the Cards theming target, and call the correct theming method.

Swift

import MaterialComponents.MaterialCards
import MaterialComponents.MaterialCards_Theming

...
 // Create a card
let card = MDCCard()
 // Create or use your app's Container Scheme
let containerScheme = MDCContainerScheme()
 // Theme the card with either default theme
card.applyTheme(withScheme: containerScheme)
 // Or outlined theme
card.applyOutlinedTheme(withScheme: containerScheme)

Objective-C

#import "MaterialCards.h"
#import "MaterialCards+Theming.h"

...
 // Create a card
MDCCard *card = [[MDCCard alloc] init];
 // Create or use your app's Container Scheme
MDCContainerScheme *containerScheme = [[MDCContainerScheme alloc] init];
 // Theme the card with either default theme
[self.card applyThemeWithScheme:containerScheme];
 // Or outlined theme
[self.card applyOutlinedThemeWithScheme:containerScheme];