components/FlexibleHeader/examples/FlexibleHeaderHorizontalPagingExample.m

/*
 Copyright 2016-present the Material Components for iOS authors. All Rights Reserved.

 Licensed under the Apache License, Version 2.0 (the "License");
 you may not use this file except in compliance with the License.
 You may obtain a copy of the License at

 http://www.apache.org/licenses/LICENSE-2.0

 Unless required by applicable law or agreed to in writing, software
 distributed under the License is distributed on an "AS IS" BASIS,
 WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
 See the License for the specific language governing permissions and
 limitations under the License.
 */

#import "FlexibleHeaderHorizontalPagingSupplemental.h"

#import "MaterialFlexibleHeader.h"

static UIColor *HexColor(uint32_t hex) {
  return [UIColor colorWithRed:(CGFloat)((uint8_t)(hex >> 16)) / (CGFloat)255
                         green:(CGFloat)((uint8_t)(hex >> 8)) / (CGFloat)255
                          blue:(CGFloat)((uint8_t)hex) / (CGFloat)255
                         alpha:1];
}

static const NSUInteger kNumberOfPages = 10;

@interface FlexibleHeaderHorizontalPagingViewController () <UIScrollViewDelegate>
@end

@implementation FlexibleHeaderHorizontalPagingViewController {
  UIScrollView *_pagingScrollView;
  NSArray *_pageScrollViews;
}

- (void)viewDidLoad {
  [super viewDidLoad];

  _pagingScrollView = [[UIScrollView alloc] initWithFrame:self.view.bounds];
  _pagingScrollView.pagingEnabled = YES;
  _pagingScrollView.delegate = self;
  _pagingScrollView.autoresizingMask =
      (UIViewAutoresizingFlexibleWidth | UIViewAutoresizingFlexibleHeight);
  _pagingScrollView.scrollsToTop = NO;
  self.title = @"Swipe Right From Left Edge to Go Back";

  NSArray *pageColors = @[ HexColor(0x55C4F5), HexColor(0x8BC34A), HexColor(0xFFC107) ];

  NSMutableArray *pageScrollViews = [NSMutableArray array];
  for (NSUInteger ix = 0; ix < kNumberOfPages; ++ix) {
    UIScrollView *scrollView = [[UIScrollView alloc] init];
    scrollView.delegate = self.fhvc;
    scrollView.backgroundColor = pageColors[ix % [pageColors count]];
    [_pagingScrollView addSubview:scrollView];

    [pageScrollViews addObject:scrollView];
  }
  _pageScrollViews = pageScrollViews;

  [self.view addSubview:_pagingScrollView];

  self.fhvc.headerView.trackingScrollView = [_pageScrollViews firstObject];

  [self typicalFlexibleHeaderViewDidLoad];
}

- (void)recalculatePageBounds {
  CGRect frame = self.view.bounds;
  for (NSUInteger ix = 0; ix < [_pageScrollViews count]; ++ix) {
    UIScrollView *scrollView = _pageScrollViews[ix];

    scrollView.frame = frame;
    scrollView.contentSize = CGSizeMake(frame.size.width, frame.size.height * 10);

    frame.origin.x += frame.size.width;
  }

  _pagingScrollView.contentSize = CGSizeMake(self.view.bounds.size.width * [_pageScrollViews count],
                                             self.view.bounds.size.height);
}

- (void)viewWillAppear:(BOOL)animated {
  [super viewWillAppear:animated];

  [self recalculatePageBounds];

  [self.navigationController setNavigationBarHidden:YES animated:animated];
}

- (void)viewWillTransitionToSize:(CGSize)size
       withTransitionCoordinator:(id<UIViewControllerTransitionCoordinator>)coordinator {
  [super viewWillTransitionToSize:size withTransitionCoordinator:coordinator];

  [self recalculatePageBounds];
}

#pragma mark - UIScrollViewDelegate

- (void)scrollViewWillBeginDragging:(UIScrollView *)scrollView {
  if (scrollView == _pagingScrollView) {
    NSInteger pageIndex = (NSInteger)(scrollView.contentOffset.x / self.view.bounds.size.width);
    for (NSInteger ix = MAX(0, pageIndex - 1);
         ix <= MIN((NSInteger)_pageScrollViews.count - 1, pageIndex + 1); ++ix) {
      if (ix != pageIndex) {
        [self.fhvc.headerView trackingScrollWillChangeToScrollView:_pageScrollViews[ix]];
      }
    }
  }
}

- (void)scrollViewDidEndDecelerating:(UIScrollView *)scrollView {
  if (scrollView == _pagingScrollView) {
    NSUInteger pageIndex = (NSUInteger)(scrollView.contentOffset.x / self.view.bounds.size.width);
    self.fhvc.headerView.trackingScrollView = _pageScrollViews[pageIndex];
    [self.fhvc.headerView.trackingScrollView flashScrollIndicators];
  }
}

#pragma mark - From the Typical Use example

- (instancetype)init {
  self = [super init];
  if (self) {
    [self commonMDCFlexibleHeaderViewControllerInit];
  }
  return self;
}

- (instancetype)initWithNibName:(NSString *)nibNameOrNil bundle:(NSBundle *)nibBundleOrNil {
  self = [super initWithNibName:nibNameOrNil bundle:nibBundleOrNil];
  if (self) {
    [self commonMDCFlexibleHeaderViewControllerInit];
  }
  return self;
}

- (instancetype)initWithCoder:(NSCoder *)aDecoder {
  self = [super initWithCoder:aDecoder];
  if (self) {
    [self commonMDCFlexibleHeaderViewControllerInit];
  }
  return self;
}

- (void)commonMDCFlexibleHeaderViewControllerInit {
  self.fhvc = [[MDCFlexibleHeaderViewController alloc] initWithNibName:nil bundle:nil];
  [self addChildViewController:_fhvc];
}

- (void)typicalFlexibleHeaderViewDidLoad {
  self.fhvc.view.frame = self.view.bounds;
  [self.view addSubview:self.fhvc.view];
  [self.fhvc didMoveToParentViewController:self];

  self.fhvc.headerView.backgroundColor = [UIColor colorWithWhite:0.1 alpha:1.0];
}

- (UIStatusBarStyle)preferredStatusBarStyle {
  return UIStatusBarStyleLightContent;
}

- (UIViewController *)childViewControllerForStatusBarHidden {
  return self.fhvc;
}

@end