material-components_material-components-ios/components/FlexibleHeader/examples/FlexibleHeaderTopLayoutGuideExample.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 <UIKit/UIKit.h>

#import "MaterialFlexibleHeader.h"
#import "supplemental/FlexibleHeaderTopLayoutGuideSupplemental.h"

@interface FlexibleHeaderTopLayoutGuideExample () <MDCFlexibleHeaderViewLayoutDelegate,
                                                   UIScrollViewDelegate>

@property(nonatomic) MDCFlexibleHeaderViewController *fhvc;
@property(nonatomic, strong) UIView *constrainedView;

@end

@implementation FlexibleHeaderTopLayoutGuideExample

- (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 {
  _fhvc = [[MDCFlexibleHeaderViewController alloc] initWithNibName:nil bundle:nil];

  // Behavioral flags.
  _fhvc.topLayoutGuideViewController = self;
  _fhvc.inferTopSafeAreaInsetFromViewController = YES;
  _fhvc.headerView.minMaxHeightIncludesSafeArea = NO;

  [self addChildViewController:_fhvc];
}

- (void)viewDidLoad {
  [super viewDidLoad];

  // Scroll view configuration
  self.scrollView = [[UIScrollView alloc] initWithFrame:self.view.bounds];
  self.scrollView.backgroundColor = [UIColor whiteColor];
  self.scrollView.autoresizingMask =
      UIViewAutoresizingFlexibleWidth | UIViewAutoresizingFlexibleHeight;
  self.scrollView.delegate = self;
  [self.view addSubview:self.scrollView];
  self.fhvc.headerView.trackingScrollView = self.scrollView;

  // Add Flexible Header View Controller to Parent View
  self.fhvc.view.frame = self.view.bounds;
  [self.view addSubview:self.fhvc.view];
  [self.fhvc didMoveToParentViewController:self];

  self.fhvc.headerView.backgroundColor = [UIColor colorWithWhite:0.1f alpha:1.0f];
  self.fhvc.headerView.shiftBehavior = MDCFlexibleHeaderShiftBehaviorEnabledWithStatusBar;

  [self setupScrollViewContent];
  [self.scrollView setScrollEnabled:YES];
  self.fhvc.layoutDelegate = self;

  // Create UIView Object
  UIView *constrainedView = [[UIView alloc] init];
  constrainedView.backgroundColor =
      [UIColor colorWithRed:11/255.0f green:232/255.0f blue:94/255.0f alpha:1];
  constrainedView.translatesAutoresizingMaskIntoConstraints = NO;
  self.constrainedView = constrainedView;
  [self.view addSubview:self.constrainedView];

  // Setup NSLayoutConstraints on View to topLayoutGuide of parent view
  NSLayoutConstraint *height =
      [NSLayoutConstraint constraintWithItem:self.constrainedView
                                   attribute:NSLayoutAttributeHeight
                                   relatedBy:NSLayoutRelationEqual
                                      toItem:nil
                                   attribute:NSLayoutAttributeNotAnAttribute
                                  multiplier:1.0
                                    constant:100];
  height.active = YES;
  NSLayoutConstraint *width = [NSLayoutConstraint constraintWithItem:self.constrainedView
                                                           attribute:NSLayoutAttributeWidth
                                                           relatedBy:NSLayoutRelationEqual
                                                              toItem:nil
                                                           attribute:NSLayoutAttributeNotAnAttribute
                                                          multiplier:1.0
                                                            constant:100];
  width.active = YES;
  NSLayoutConstraint *top = [NSLayoutConstraint constraintWithItem:self.constrainedView
                                                         attribute:NSLayoutAttributeTop
                                                         relatedBy:NSLayoutRelationEqual
                                                            toItem:self.topLayoutGuide
                                                         attribute:NSLayoutAttributeBottom
                                                        multiplier:1.0
                                                          constant:0];
  top.active = YES;
  NSLayoutConstraint *leading = [NSLayoutConstraint constraintWithItem:self.constrainedView
                                                             attribute:NSLayoutAttributeLeading
                                                             relatedBy:NSLayoutRelationEqual
                                                                toItem:self.view
                                                             attribute:NSLayoutAttributeLeading
                                                            multiplier:1.0
                                                              constant:0];
  leading.active = YES;
}

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

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

// This method must be implemented for MDCFlexibleHeaderViewController's
// MDCFlexibleHeaderView to properly support MDCFlexibleHeaderShiftBehavior should you choose
// to customize it.
- (UIViewController *)childViewControllerForStatusBarHidden {
  return self.fhvc;
}

#pragma mark - MDCFlexibleHeaderViewLayoutDelegate

- (void)flexibleHeaderViewController:(MDCFlexibleHeaderViewController *)flexibleHeaderViewController
    flexibleHeaderViewFrameDidChange:(MDCFlexibleHeaderView *)flexibleHeaderView {
  // Called whenever the frame changes.
}

#pragma mark - UIScrollViewDelegate

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

- (void)scrollViewDidEndDecelerating:(UIScrollView *)scrollView {
  if (scrollView == self.fhvc.headerView.trackingScrollView) {
    [self.fhvc.headerView trackingScrollViewDidEndDecelerating];
  }
}

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

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

@end