material-components_material-components-ios/components/Cards

Cards

Cards contain content and actions about a single subject. They can be used standalone, or as part of a list. Cards are meant to be interactive, and aren't meant to be be used solely for style purposes.

Design & API documentation

• Material Design guidelines: Cards
• Class: MDCCard
• Class: MDCCardCollectionCell
• Enumeration: Enumerations
• Enumeration: MDCCardCellHorizontalImageAlignment
• Enumeration: MDCCardCellState
• Enumeration: MDCCardCellVerticalImageAlignment

Table of contents

• Overview
  • Cards Classes
• Installation
  • Installation with CocoaPods
  • Importing
• Usage
  • Typical use: as a view
  • Typical use: in a collection view
• Extensions
  • Color Theming
  • Shape Theming
• Accessibility
  • Card Accessibility

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Overview

Cards provides two different versions, MDCCard inheriting from UIControl and MDCCardCollectionCell inheriting 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.

MDCCardThemer exposes apis to theme MDCCard and MDCCardCollectionCell instances as either a default or outlined variant. An outlined variant behaves identically to a default styled card, but differs in its coloring and in that it has a stroked border. Use 'applyScheme:toCard:' to style an instance with default values and 'applyOutlinedVariantWithScheme:toCard:' to style an instance with the outlined values.

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.

Installation

Installation with CocoaPods

Add the following to your Podfile:

pod 'MaterialComponents/Cards'

Then, run the following command:

pod install

Importing

To import the component:

Swift

import MaterialComponents.MaterialCards

Objective-C

#import "MaterialCards.h"

Usage

Typical use: as a view

MDCCard can be used like a regular UIView.

Swift

let card = MDCCard()

// Create, position, and add content views:
let imageView = UIImageView()
card.addSubview(imageView)

Objective-C

MDCCard *card = [[MDCCard alloc] init];

// Create, position, and add content views:
UIImageView *imageView = [[UIImageView alloc] init];
[card addSubview:imageView];

Typical use: in a collection view

Use MDCCardCollectionCell as a base class for your custom collection view cell

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.selectedImageTintColor = .blue
  cell.cornerRadius = 8
  cell.setShadowElevation(6, for: .selected)
  cell.setShadowColor(UIColor.black, for: .highlighted)
  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 setSelectedImageTintColor:[UIColor blueColor]];
  [cell setCornerRadius:8.f];
  [cell setShadowElevation:6.f forState:MDCCardCellStateSelected];
  [cell setShadowColor:[UIColor blackColor] forState:MDCCardCellStateHighlighted];
}

Extensions

Color Theming

You can theme a card with your app's color scheme using the ColorThemer extension.

You must first add the Color Themer extension to your project:

pod 'MaterialComponents/Cards+ColorThemer'

Swift

// Step 1: Import the ColorThemer extension
import MaterialComponents.MaterialCards_ColorThemer

// Step 2: Create or get a color scheme
let colorScheme = MDCSemanticColorScheme()

// Step 3: Apply the color scheme to your component
MDCCardsColorThemer.applySemanticColorScheme(colorScheme, to: component)

Objective-C

// Step 1: Import the ColorThemer extension
#import "MaterialCards+ColorThemer.h"

// Step 2: Create or get a color scheme
id<MDCColorScheming> colorScheme = [[MDCSemanticColorScheme alloc] init];

// Step 3: Apply the color scheme to your component
[MDCCardsColorThemer applySemanticColorScheme:colorScheme
     toCard:component];

Shape Theming

You can theme a card with your app's shape scheme using the ShapeThemer extension.

You must first add the ShapeThemer extension to your project:

pod 'MaterialComponents/Cards+ShapeThemer'

Swift

// Step 1: Import the ShapeThemer extension
import MaterialComponents.MaterialCards_ShapeThemer

// Step 2: Create or get a shape scheme
let shapeScheme = MDCShapeScheme()

// Step 3: Apply the shape scheme to your component
MDCCardsShapeThemer.applyShapeScheme(shapeScheme, to: component)

Objective-C

// Step 1: Import the ShapeThemer extension
#import "MaterialCards+ShapeThemer.h"

// Step 2: Create or get a shape scheme
id<MDCShapeScheming> shapeScheme = [[MDCShapeScheme alloc] init];

// Step 3: Apply the shape scheme to your component
[MDCCardsShapeThemer applyShapeScheme:shapeScheme
     toCard:component];

Accessibility

Card Accessibility

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.