material-components_material-components-ios/components/AppBar/examples/AppBarTypicalCollectionViewExample.m

/*
 Copyright 2018-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 <UIKit/UIKit.h>

#import "MaterialAppBar.h"
#import "MaterialAppBar+ColorThemer.h"
#import "MaterialAppBar+TypographyThemer.h"

@interface AppBarTypicalCollectionViewExample : UICollectionViewController

// Step 1: Create an App Bar.
@property(nonatomic, strong) MDCAppBar *appBar;

@property(nonatomic, strong) MDCSemanticColorScheme *colorScheme;
@property(nonatomic, strong) MDCTypographyScheme *typographyScheme;

@end
@implementation AppBarTypicalCollectionViewExample

- (id)init {
  UICollectionViewFlowLayout *layout = [[UICollectionViewFlowLayout alloc] init];
  layout.minimumInteritemSpacing = 10.0f;

  self = [super initWithCollectionViewLayout:layout];

  if (self) {
    self.title = @"App Bar";

    // Step 2: Initialize the App Bar and add the headerViewController as a child.
    _appBar = [[MDCAppBar alloc] init];
    [self addChildViewController:_appBar.headerViewController];
  }
  return self;
}

- (void)viewDidLoad {
  [super viewDidLoad];
  // Collection view setup
  self.collectionView.dataSource = self;
  self.collectionView.delegate = self;
  self.collectionView.backgroundColor = [UIColor whiteColor];
  self.collectionView.contentInset = UIEdgeInsetsMake(4, 8, 4, 8);
  [self.collectionView registerClass:[UICollectionViewCell class]
          forCellWithReuseIdentifier:@"Cell"];

  // Recommended step: Set the tracking scroll view.
  MDCFlexibleHeaderView *headerView = self.appBar.headerViewController.headerView;
  headerView.trackingScrollView = self.collectionView;
  headerView.minimumHeight = 64;
  headerView.maximumHeight = 200;

  [self.appBar addSubviewsToParent];
  [MDCAppBarTypographyThemer applyTypographyScheme:self.typographyScheme toAppBar:_appBar];
  [MDCAppBarColorThemer applySemanticColorScheme:self.colorScheme toAppBar:_appBar];
}


- (NSInteger)collectionView:(UICollectionView *)collectionView
     numberOfItemsInSection:(NSInteger)section {
  return 100;
}

- (__kindof UICollectionViewCell *)collectionView:(UICollectionView *)collectionView
                           cellForItemAtIndexPath:(NSIndexPath *)indexPath {
  UICollectionViewCell *cell =
      [collectionView dequeueReusableCellWithReuseIdentifier:@"Cell" forIndexPath:indexPath];
  switch (indexPath.row%3) {
    case 0:
      cell.backgroundColor = [UIColor colorWithWhite:0.2f alpha:1.0f];
      break;
    case 1:
      cell.backgroundColor = [UIColor colorWithWhite:0.5f alpha:1.0f];
      break;
    case 2:
      cell.backgroundColor = [UIColor colorWithWhite:0.7f alpha:1.0f];
      break;
    default:
      break;
  }

  return cell;
}

- (CGSize)collectionView:(UICollectionView *)collectionView
                  layout:(UICollectionViewLayout*)collectionViewLayout
  sizeForItemAtIndexPath:(NSIndexPath *)indexPath {
  CGRect collectionViewFrame = collectionView.frame;
  return CGSizeMake(collectionViewFrame.size.width/2.f - 14.f, 40.f);
}

#pragma mark - UIScrollViewDelegate

- (void)scrollViewDidScroll:(UIScrollView *)scrollView {
  MDCFlexibleHeaderView *headerView = self.appBar.headerViewController.headerView;
  if (scrollView == headerView.trackingScrollView) {
    [headerView trackingScrollViewDidScroll];
  }
}

- (void)scrollViewDidEndDragging:(UIScrollView *)scrollView willDecelerate:(BOOL)decelerate {
  MDCFlexibleHeaderView *headerView = self.appBar.headerViewController.headerView;
  if (scrollView == headerView.trackingScrollView) {
    [headerView trackingScrollViewDidEndDraggingWillDecelerate:decelerate];
  }
}

- (void)scrollViewDidEndDecelerating:(UIScrollView *)scrollView {
  MDCFlexibleHeaderView *headerView = self.appBar.headerViewController.headerView;
  if (scrollView == headerView.trackingScrollView) {
    [headerView trackingScrollViewDidEndDecelerating];
  }
}
- (void)scrollViewWillEndDragging:(UIScrollView *)scrollView
                     withVelocity:(CGPoint)velocity
              targetContentOffset:(inout CGPoint *)targetContentOffset {
  MDCFlexibleHeaderView *headerView = self.appBar.headerViewController.headerView;
  if (scrollView == headerView.trackingScrollView) {
    [headerView trackingScrollViewWillEndDraggingWithVelocity:velocity
                                          targetContentOffset:targetContentOffset];
  }
}

- (UIStatusBarStyle)preferredStatusBarStyle {
  return UIStatusBarStyleLightContent;
}

@end

@implementation AppBarTypicalCollectionViewExample (CatalogByConvention)

+ (NSArray *)catalogBreadcrumbs {
  return @[ @"App Bar", @"Collection View with App bar" ];
}

+ (BOOL)catalogIsPrimaryDemo {
  return NO;
}

- (BOOL)catalogShouldHideNavigation {
  return YES;
}

+ (BOOL)catalogIsPresentable {
  return YES;
}

@end