components/Collections/examples/CollectionsSectionInsetsExample.m

/*
 Copyright 2017-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 "supplemental/CollectionsSectionInsetsExampleSupplemental.h"

@implementation CollectionsSectionInsetsExample

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

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

- (instancetype)initWithCollectionViewLayout:(UICollectionViewLayout *)layout {
  if (self = [super initWithCollectionViewLayout:layout]) {
    [self collectionsSectionInsetsExampleCommonInit];
  }
  return self;
}

- (void)collectionsSectionInsetsExampleCommonInit {
  _content = [NSMutableArray array];
  _sectionUsesCustomInsets = [NSMutableDictionary dictionaryWithCapacity:kSectionCount];
}

- (UICollectionViewCell *)collectionView:(UICollectionView *)collectionView
                  cellForItemAtIndexPath:(NSIndexPath *)indexPath {
  MDCCollectionViewTextCell *cell =
      [collectionView dequeueReusableCellWithReuseIdentifier:kReusableIdentifierItem
                                                forIndexPath:indexPath];
  cell.textLabel.text = self.content[indexPath.section][indexPath.item];
  cell.accessibilityIdentifier =
      [NSString stringWithFormat:@"%ld.%ld", (long)indexPath.section, (long)indexPath.row];
  if (indexPath.row == 0) {
    UISwitch *switchControl = [[UISwitch alloc] initWithFrame:CGRectZero];
    [switchControl setOn:[self.sectionUsesCustomInsets[@(indexPath.section)] boolValue]];
    [switchControl addTarget:self
                      action:@selector(didSet:)
            forControlEvents:UIControlEventValueChanged];
    switchControl.tag = indexPath.section;

    cell.accessoryView = switchControl;
  }

  return cell;
}

#pragma mark - <UICollectionViewDelegateFlowLayout>

- (UIEdgeInsets)collectionView:(UICollectionView *)collectionView
                        layout:(UICollectionViewLayout *)collectionViewLayout
        insetForSectionAtIndex:(NSInteger)section {
  UIEdgeInsets insets = [super collectionView:collectionView
                                       layout:collectionViewLayout
                       insetForSectionAtIndex:section];
  if ([self.sectionUsesCustomInsets[@(section)] boolValue]) {
    insets.left = MIN(40, 8 * section);
    insets.right = insets.left;
  }
  return insets;
}

#pragma mark - UIControlEventHandlers

- (void)didSet:(UISwitch *)sender {
  NSUInteger section = sender.tag;
  self.sectionUsesCustomInsets[@(section)] = @(sender.isOn);
  [self.collectionView.collectionViewLayout invalidateLayout];
}

@end