README.md

Page control

This control is designed to be a drop-in replacement for UIPageControl, with a user experience influenced by Material Design specifications for animation and layout. The API methods are the same as a UIPageControl, with the addition of a few key methods required to achieve the desired animation of the control.

Design & API documentation

• Class: MDCPageControl

Table of contents

• Overview
• Installation
  • Installation with CocoaPods
  • Importing
• Usage
  • Typical use
  • Differences From UIPageControl
• Extensions
  • Color Theming

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Overview

Page control showing current page in resting state.

Page control showing animated track with current page indicator positioned along the track.

Page control showing new current page.

Installation

Installation with CocoaPods

Add the following to your Podfile:

pod 'MaterialComponents/PageControl'

Then, run the following command:

pod install

Importing

To import the component:

Swift

import MaterialComponents.MaterialPageControl

Objective-C

#import "MaterialPageControl.h"

Usage

Typical use

Integrating the page control requires two steps. First, add a page control with companion scroll view, and second, forward the scroll view delegate methods to the page control.

Step 1: Add the page control to a view

Add the page control to a view and set the desired page control properties. This step is done similarly to a native UIPageControl. In addition, provide a tap gesture handler for the control to to fire off the UIControlEventValueChanged events in which the scroll view would typically be notified of page changes.

Swift

let pageControl = MDCPageControl()
let scrollView = UIScrollView()
let pages = NSMutableArray()

override func viewDidLoad() {
  super.viewDidLoad()

  scrollView.delegate = self
  view.addSubview(scrollView)

  pageControl.numberOfPages = 3

  let pageControlSize = pageControl.sizeThatFits(view.bounds.size)
  pageControl.frame = CGRect(x: 0, y: view.bounds.height - pageControlSize.height, width: view.bounds.width, height: pageControlSize.height)

  pageControl.addTarget(self, action: #selector(didChangePage), for: .valueChanged)
  pageControl.autoresizingMask = [.flexibleTopMargin, .flexibleWidth]
  view.addSubview(pageControl)
}

func didChangePage(sender: MDCPageControl){
  var offset = scrollView.contentOffset
  offset.x = CGFloat(sender.currentPage) * scrollView.bounds.size.width;
  scrollView.setContentOffset(offset, animated: true)
}

Objective-C

- (void)viewDidLoad {
  [super viewDidLoad];

  self.scrollView.delegate = self;
  [self.view addSubview:self.scrollView];

  self.pageControl.numberOfPages = 3;

  CGSize pageControlSize = [self.pageControl sizeThatFits:self.view.bounds.size];
  self.pageControl.frame = CGRectMake(0, self.view.bounds.size.height - pageControlSize.height, self.view.bounds.size.width, pageControlSize.height);

  [self.pageControl addTarget:self action:@selector(didChangePage:) forControlEvents: UIControlEventValueChanged];
  self.pageControl.autoresizingMask = UIViewAutoresizingFlexibleWidth | UIViewAutoresizingFlexibleTopMargin;
  [self.view addSubview:self.pageControl];

}

- (void)didChangePage:(MDCPageControl*)sender {
  CGPoint offset = self.scrollView.contentOffset;
  offset.x = (CGFloat)sender.currentPage * self.scrollView.bounds.size.width;
  [self.scrollView setContentOffset:offset animated: true];
}

Step 2: Forwarding the required scroll view delegate methods

This page control is designed to be used in conjunction with a scroll view. To achieve the desired page control animation effects, there are three scroll view delegate methods that must be forwarded to the page control (-scrollViewDidScroll, -scrollViewDidEndDecelerating, and -scrollViewDidEndScrollingAnimation). This allows the page control to keep in sync with the scrolling movement of the designated scroll view.

Swift

func scrollViewDidScroll(_ scrollView: UIScrollView) {
  pageControl.scrollViewDidScroll(scrollView)
}

func scrollViewDidEndDecelerating(_ scrollView: UIScrollView) {
  pageControl.scrollViewDidEndDecelerating(scrollView)
}

func scrollViewDidEndScrollingAnimation(_ scrollView: UIScrollView) {
  pageControl.scrollViewDidEndScrollingAnimation(scrollView)
}

Objective-C

- (void)scrollViewDidScroll:(UIScrollView *)scrollView {
  [self.pageControl scrollViewDidScroll:scrollView];
}

- (void)scrollViewDidEndDecelerating:(UIScrollView *)scrollView {
  [self.pageControl scrollViewDidEndDecelerating:scrollView];
}

- (void)scrollViewDidEndScrollingAnimation:(UIScrollView *)scrollView {
  [self.pageControl scrollViewDidEndScrollingAnimation:scrollView];
}

Differences From UIPageControl

This page control provides an animation effect that keeps a page indicator in sync with the scrolling of a designated scroll view. This is in contrast to a native UIPageControl, which shows the current page indicator without any animated transitions between changes.

As the user scrolls, a track will be drawn with animation from the current indicator position towards the next indicator position that is being scrolled towards. The current indicator will float along this track and position itself based on the percent scrolled between the pages. When the scroll view finishes scrolling, the track will disappear with animation towards the final position of the new page.

Extensions

Color Theming

Page Control does not yet have a Material Design color system themer. The following tasks are tracking its development:

• Task: Implement a color themer