components/HeaderStackView/src/MDCHeaderStackView.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 <CoreGraphics/CoreGraphics.h>

#import "MDCHeaderStackView.h"

static NSString *const MDCHeaderStackViewTopBarKey = @"MDCHeaderStackViewTopBarKey";
static NSString *const MDCHeaderStackViewBottomBarKey = @"MDCHeaderStackViewBottomBarKey";

@implementation MDCHeaderStackView

- (instancetype)initWithCoder:(NSCoder *)aDecoder {
  self = [super initWithCoder:aDecoder];
  if (self) {
    if ([aDecoder containsValueForKey:MDCHeaderStackViewTopBarKey]) {
      _topBar = [aDecoder decodeObjectOfClass:[UIView class] forKey:MDCHeaderStackViewTopBarKey];
    }

    if ([aDecoder containsValueForKey:MDCHeaderStackViewBottomBarKey]) {
      _bottomBar = [aDecoder decodeObjectOfClass:[UIView class]
                                          forKey:MDCHeaderStackViewBottomBarKey];
    }
  }
  return self;
}

- (void)encodeWithCoder:(NSCoder *)aCoder {
  [super encodeWithCoder:aCoder];
  if (self.topBar) {
    [aCoder encodeObject:self.topBar forKey:MDCHeaderStackViewTopBarKey];
  }
  if (self.bottomBar) {
    [aCoder encodeObject:self.bottomBar forKey:MDCHeaderStackViewBottomBarKey];
  }
}

- (CGSize)sizeThatFits:(CGSize)size {
  if (_bottomBar) {
    size.height = [_bottomBar sizeThatFits:size].height;
  } else {
    size.height = [_topBar sizeThatFits:size].height;
  }
  return size;
}

- (void)layoutSubviews {
  [super layoutSubviews];

  CGSize boundsSize = self.bounds.size;

  CGSize bottomBarSize = [_bottomBar sizeThatFits:boundsSize];
  CGFloat remainingHeight = boundsSize.height - bottomBarSize.height;
  CGSize topBarSize = [_topBar sizeThatFits:CGSizeMake(boundsSize.width, remainingHeight)];
  remainingHeight -= topBarSize.height;

  CGRect topBarFrame = CGRectMake(0, 0, topBarSize.width, topBarSize.height);
  CGRect bottomBarFrame = CGRectMake(0, 0, bottomBarSize.width, bottomBarSize.height);

  if (remainingHeight > 0) {
    // Expand the top bar to fill the remaining height.
    topBarFrame.size.height += remainingHeight;

  } else if (remainingHeight < 0) {
    // Negative value causes the top bar to slide up and away.
    topBarFrame.origin.y += remainingHeight;
  }
  bottomBarFrame.origin.y = CGRectGetMaxY(topBarFrame);

  _topBar.frame = topBarFrame;
  _bottomBar.frame = bottomBarFrame;
}

#pragma mark - Public

- (void)setTopBar:(UIView *)topBar {
  if (_topBar == topBar) {
    return;
  }

  [_topBar removeFromSuperview];

  _topBar = topBar;

  [self addSubview:_topBar];
  [self setNeedsLayout];
}

- (void)setBottomBar:(UIView *)bottomBar {
  if (_bottomBar == bottomBar) {
    return;
  }

  [_bottomBar removeFromSuperview];

  _bottomBar = bottomBar;

  [self addSubview:_bottomBar];
  [self setNeedsLayout];
}

@end