material-components_material-components-ios/components/Tabs/examples/BottomNavigationBarExample.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 "MaterialColorScheme.h"
#import "MaterialTabs.h"
#import "MaterialTabs+ColorThemer.h"

@interface BottomNavigationBarExample : UIViewController <MDCTabBarDelegate>
@property(nonatomic, strong) MDCSemanticColorScheme *colorScheme;
@end

@implementation BottomNavigationBarExample {
  MDCTabBar *_bottomNavigationBar;
  NSArray<UIColor *> *_colors;
}

- (id)init {
  self = [super init];
  if (self) {
    self.colorScheme = [[MDCSemanticColorScheme alloc] init];
  }
  return self;
}

- (void)viewDidLoad {
  [super viewDidLoad];

  _bottomNavigationBar = [[MDCTabBar alloc] initWithFrame:CGRectZero];
  _bottomNavigationBar.translatesAutoresizingMaskIntoConstraints = NO;
  _bottomNavigationBar.delegate = self;
  [MDCTabBarColorThemer applySemanticColorScheme:self.colorScheme toTabs:_bottomNavigationBar];
  
  _bottomNavigationBar.inkColor = [UIColor colorWithRed:0 green:0.5f blue:0 alpha:0.15f];

  NSBundle *bundle = [NSBundle bundleForClass:[BottomNavigationBarExample class]];
  UIImage *infoImage =
      [UIImage imageNamed:@"TabBarDemo_ic_info" inBundle:bundle compatibleWithTraitCollection:nil];
  UIImage *starImage =
      [UIImage imageNamed:@"TabBarDemo_ic_star" inBundle:bundle compatibleWithTraitCollection:nil];
  _bottomNavigationBar.items = @[
    [[UITabBarItem alloc] initWithTitle:@"Red" image:infoImage tag:0],
    [[UITabBarItem alloc] initWithTitle:@"Blue" image:starImage tag:0]
  ];

  _colors = @[
    [UIColor colorWithRed:0.5 green:0 blue:0 alpha:1],
    [UIColor colorWithRed:0 green:0 blue:0.5 alpha:1]
  ];

  [self.view addSubview:_bottomNavigationBar];
  [self updateDisplay];

  [NSLayoutConstraint constraintWithItem:_bottomNavigationBar
                               attribute:NSLayoutAttributeBottom
                               relatedBy:NSLayoutRelationEqual
                                  toItem:self.view
                               attribute:NSLayoutAttributeBottom
                              multiplier:1
                                constant:0].active = YES;
  [NSLayoutConstraint constraintWithItem:_bottomNavigationBar
                               attribute:NSLayoutAttributeLeft
                               relatedBy:NSLayoutRelationEqual
                                  toItem:self.view
                               attribute:NSLayoutAttributeLeft
                              multiplier:1
                                constant:0].active = YES;
  [NSLayoutConstraint constraintWithItem:_bottomNavigationBar
                               attribute:NSLayoutAttributeRight
                               relatedBy:NSLayoutRelationEqual
                                  toItem:self.view
                               attribute:NSLayoutAttributeRight
                              multiplier:1
                                constant:0].active = YES;
}

#pragma mark - MDCTabBarDelegate

- (void)tabBar:(MDCTabBar *)tabBar didSelectItem:(UITabBarItem *)item {
  [self updateDisplay];
}

#pragma mark - UIBarPositioningDelegate

- (UIBarPosition)positionForBar:(id<UIBarPositioning>)bar {
  return UIBarPositionBottom;
}

#pragma mark - Private

- (void)updateDisplay {
  UITabBarItem *selectedItem = _bottomNavigationBar.selectedItem;
  if (!selectedItem) {
    return;
  }

  NSUInteger selectedIndex = [_bottomNavigationBar.items indexOfObject:selectedItem];
  if (selectedIndex == NSNotFound) {
    return;
  }

  self.view.backgroundColor = _colors[selectedIndex];
}

@end

@implementation BottomNavigationBarExample (CatalogByConvention)

+ (NSDictionary *)catalogMetadata {
  return @{
    @"breadcrumbs": @[ @"Tab Bar", @"Bottom Navigation" ],
    @"primaryDemo": @NO,
    @"presentable": @NO,
  };
}

@end