Tabs

Tabs organize content across different screens, data sets, and other interactions.

Contents

• Using tabs
• Fixed tabs
• Scrollable tabs
• Theming
• Migrating from legacy tabs

Using tabs

Installing

In order to use MDCTabBarView, first add the component to your Podfile:

pod MaterialComponents/Tabs+TabBarView

Then, run pod install:

pod install

After that, import the relevant target or file.

Swift

import MaterialComponents.MaterialTabs_TabBarView

Objective-C

#import <MaterialComponents/MaterialTabs+TabBarView.h>

From there, initialize an MDCTabBarView and add it to your view controller's view.

Making tabs accessible

MDCTabBarView is accessible by default. VoiceOver reads the titles of the UITabBarItems contained within a tab bar as accessibilityLabels, and the MDCTabBarView handles setting the accessibilityTraits when tab bar items become selected and unselected.

Types

Material tabs can be broken into two main categories: 1. Fixed tabs 2. Scrollable tabs

Tabs example

MDCTabBarView supports both fixed and scrolling tabs. By default, MDCTabbarView has a fixed layout. To set it up for scrolling, set the preferredLayoutStyle property to .scrollable. To receive updates about user actions, set the delegate property to an object conforming to MDCTabBarViewDelegate. Here is a simple set up of an MDCTabBarView:

Swift

let tabBarView = MDCTabBarView()
tabBarView.items = [
  UITabBarItem(title: "Recents", image: UIImage(named: "phone"), tag: 0),
  UITabBarItem(title: "Favorites", image: UIImage(named: "heart"), tag: 0),
]
tabBarView.preferredLayoutStyle = .scrollable // or .fixed
view.addSubview(tabBarView)
// Configure constraints

Objective-C

MDCTabBarView *tabBarView = [[MDCTabBarView alloc] init];
tabBarView.items = @[
    [[UITabBarItem alloc] initWithTitle:@"Recents" image:[UIImage imageNamed:@"phone"] tag:0],
    [[UITabBarItem alloc] initWithTitle:@"Favorites" image:[UIImage imageNamed:@"heart"] tag:0],
];
tabBarView.preferredLayoutStyle = MDCTabBarViewLayoutStyleScrollable; // or MDCTabBarViewLayoutStyleFixed
[self.view addSubview:tabBarView];
// Configure constraints

Tabs anatomy

Tab bars contain tab bar items with optional icons and text labels. Tab bar items can be selected or unselected. The selection indicator appears below the currently selected tab bar item.

1. Container
2. Selected icon (optional if there’s a label)
3. Selected text label (optional if there’s an icon)
4. Selection indicator
5. Unselected icon (optional if there’s a label)
6. Unselected text label (optional if there’s an icon)
7. Tab bar item

Container attributes

Tab item icon attributes

Tab item text label attributes

Tab item container attributes

Tab indicator attributes

Theming

Tabs supports Material Theming using a Container Scheme. To learn more about theming extensions, see here. Below is a screenshot of an MDCTabBarView with the Material Design Shrine theme:

Tabs theming example

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

pod MaterialComponents/Tabs+TabBarViewTheming

Then Run the installer:

pod install

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

Swift

import MaterialComponents.MaterialTabs_TabBarViewTheming
...

// Create an MDCTabbarView
let tabBar = MDCTabBarView()
// Create or use your app's Container Scheme
let containerScheme = MDCContainerScheme()
// Theme the tab bar with either Primary Theme
tabBar.applyPrimaryTheme(withScheme: containerScheme)
// Or Surface Theme
tabBar.applySurfaceTheme(withScheme: containerScheme)

Objective-C

// Import the Tabs Theming Extensions header
#import <MaterialComponents/MaterialTabs+TabBarViewTheming.h>
...
// Create or use your app's Container Scheme
MDCContainerScheme *containerScheme = [[MDCContainerScheme alloc] init];
// Theme the tab bar with either Primary Theme
[self.tabBar applyPrimaryThemeWithScheme:containerScheme];
// Or Surface Theme
[self.tabBar applySurfaceThemeWithScheme:containerScheme];

Migrating from legacy tabs

Below are some of the differences between MDCTabBarView and its predecessor, MDCTabBar. If you have been using MDCTabBar, make note of the following changes.

Subclassing Restricted

Subclassing is not supported by MDCTabBarView. Any requirements that you have for Material Tabs that are not met by the public APIs should be filed as a feature request or bug against MDCTabBarView.

Selected Item Behavior

MDCTabBarView does not automatically mark any item as selected when the items array is set, unless the previously-selected item is in the new items array. This is a change from MDCTabBar, but ensures that the view and its APIs present equivalent information.

Colors, Fonts, and Theming

To set the image tint colors, use - setImageTintColor:forState:. The MDCTabBar APIs, - selectedItemTintColor and - unselectedItemTintColor are unavailable.

To set the fonts of the labels, use - setTitleFont:forState:. The MDCTabBar APIs, - selectedItemTitleFont and - unselectedItemTitleFont are unavailable. Note that the tab bar may adjust the sizes of its views to account for changes in fonts, and that can result in unexpected changes from Fixed Tabs to Scrollable Tabs depending on font choices and title length.

MDCTabBarView uses Material Ripple by default (MDCRippleView) and does not support Ink. You may configure the Ripple color for touch feedback by setting the - rippleColor property.

Alignment and Item Rendering

The MDCTabBar API itemAppearance has no equivalent on MDCTabBarView. Whatever relevant properties (e.g., title, image) are provided on UITabBarItem should be used instead.

The MDCTabBar APIs displaysUppercaseTitles and titleTextTransform have no equivalent in MDCTabBarView. Titles are rendered as set on UITabBarItem and accessibilityLabel should be set on the item if the title text is not correctly handled by UIAccessibility.

UIBarPositioningDelegate

MDCTabBarView no longer conforms to UIBarPositioning, since Material Tabs are always positioned above their related content views. As a result, MDCTabBarViewDelegate does not inherit from UIBarPositioningDelegate.

Selection Indicator Template

The Selection Indicator Template APIs and protocols are copied nearly verbatim from MDCTabBar, with the names changed to prevent collision. One difference is the expected behavior of contentFrame as used by the indicator template. In MDCTabBar the value of contentFrame was the union of the title and image frames. However, in MDCTabBarView the width of the contentFrame is always the width of the title (when present), and the height will include both the title and image. This change is necessary to support internal clients.

Custom Views

Features like badges and horizontal layout of titles and images are not supported on MDCTabBarView. Clients who need such behavior should implement their own custom UIView and assign it to the mdc_customView property of a UITabBarItem sublcass that conforms to MDCTabBarItemCustomViewing. A simple subclass conforming to the MDCTabBarItemCustomViewing protocol is provided as MDCTabBarItem.

Swift

let customView = MyCustomTabView()
let customItem = MDCTabBarItem()
customItem.mdc_customView = customView
let tabBarView = MDCTabBarView()
tabBarView.items = [ customItem ]

Objective-C

MyCustomTabView *customView = [[MyCustomTabView alloc] init];
MDCTabBarItem *customItem = [[MDCTabBarItem alloc] init];
customItem.mdc_customView = customView;
MDCTabBarView *tabBarView = [[MDCTabBarView alloc] init];
tabBarView.items = @[ customItem ]