components/Collections/examples/CollectionsHeaderFooterExample.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 "MaterialTypography.h"
#import "supplemental/CollectionsHeaderFooterExample.h"

static const NSInteger kSectionCount = 3;
static const NSInteger kSectionItemCount = 2;
static NSString *const kReusableIdentifierItem = @"itemCellIdentifier";

@implementation CollectionsHeaderFooterExample {
  NSMutableArray <NSMutableArray *>*_content;
}

- (void)viewDidLoad {
  [super viewDidLoad];

  // Register cell.
  [self.collectionView registerClass:[MDCCollectionViewTextCell class]
          forCellWithReuseIdentifier:kReusableIdentifierItem];

  // Register header.
  [self.collectionView registerClass:[MDCCollectionViewTextCell class]
          forSupplementaryViewOfKind:UICollectionElementKindSectionHeader
                 withReuseIdentifier:UICollectionElementKindSectionHeader];

  // Register footer.
  [self.collectionView registerClass:[MDCCollectionViewTextCell class]
          forSupplementaryViewOfKind:UICollectionElementKindSectionFooter
                 withReuseIdentifier:UICollectionElementKindSectionFooter];

  // Populate content.
  _content = [NSMutableArray array];
  for (NSInteger i = 0; i < kSectionCount; i++) {
    NSMutableArray *items = [NSMutableArray array];
    for (NSInteger j = 0; j < kSectionItemCount; j++) {
      NSString *itemString = [NSString stringWithFormat:@"Section-%ld Item-%ld", (long)i, (long)j];
      [items addObject:itemString];
    }
    [_content addObject:items];
  }

  // Customize collection view settings.
  self.styler.cellStyle = MDCCollectionViewCellStyleCard;
}

#pragma mark - <UICollectionViewDataSource>

- (NSInteger)numberOfSectionsInCollectionView:(UICollectionView *)collectionView {
  return [_content count];
}

- (NSInteger)collectionView:(UICollectionView *)collectionView
     numberOfItemsInSection:(NSInteger)section {
  return [_content[section] count];
}

- (UICollectionViewCell *)collectionView:(UICollectionView *)collectionView
                  cellForItemAtIndexPath:(NSIndexPath *)indexPath {
  MDCCollectionViewTextCell *cell =
      [collectionView dequeueReusableCellWithReuseIdentifier:kReusableIdentifierItem
                                                forIndexPath:indexPath];
  cell.textLabel.text = _content[indexPath.section][indexPath.item];
  return cell;
}

- (UICollectionReusableView *)collectionView:(UICollectionView *)collectionView
           viewForSupplementaryElementOfKind:(NSString *)kind
                                 atIndexPath:(NSIndexPath *)indexPath {
  MDCCollectionViewTextCell *supplementaryView =
      [collectionView dequeueReusableSupplementaryViewOfKind:kind
                                         withReuseIdentifier:kind
                                                forIndexPath:indexPath];

  if ([kind isEqualToString:UICollectionElementKindSectionHeader]) {
    if (indexPath.section == 0) {
      supplementaryView.textLabel.text = @"Section with only header";
    } else {
      supplementaryView.textLabel.text = @"Section header";
    }
  } else if ([kind isEqualToString:UICollectionElementKindSectionFooter]) {
    if (indexPath.section == 1) {
      supplementaryView.textLabel.text = @"Section with only footer";
    } else {
      supplementaryView.textLabel.text = @"Section footer";
    }
  }

  return supplementaryView;
}

#pragma mark - <UICollectionViewDelegateFlowLayout>

- (CGSize)collectionView:(UICollectionView *)collectionView
                             layout:(UICollectionViewLayout *)collectionViewLayout
    referenceSizeForHeaderInSection:(NSInteger)section {
  if (section == 0 || section == 2) {
    return CGSizeMake(collectionView.bounds.size.width, MDCCellDefaultOneLineHeight);
  }
  return CGSizeZero;
}

- (CGSize)collectionView:(UICollectionView *)collectionView
                             layout:(UICollectionViewLayout *)collectionViewLayout
    referenceSizeForFooterInSection:(NSInteger)section {
  if (section > 0) {
    return CGSizeMake(collectionView.bounds.size.width, MDCCellDefaultOneLineHeight);
  }
  return CGSizeZero;
}

#pragma mark - <MDCCollectionViewStylingDelegate>

- (BOOL)collectionView:(UICollectionView *)collectionView
    shouldHideFooterBackgroundForSection:(NSInteger)section {
  return (section == 2);
}

#pragma mark - CatalogByConvention

+ (NSArray *)catalogBreadcrumbs {
  return @[ @"Collections", @"Header / Footer Demo" ];
}

+ (BOOL)catalogIsPrimaryDemo {
  return NO;
}

+ (BOOL)catalogIsPresentable {
  return NO;
}

@end