components/Tabs/src/TabBarView/private/MDCTabBarViewIndicatorView.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 "MDCTabBarViewIndicatorView.h"

#import "MDCTabBarViewIndicatorAttributes.h"

/** Content view that displays a filled path and supports animation between states. */
@interface MDCTabBarViewIndicatorShapeView : UIView

/** The path to display. It will be filled using the view's tintColor. */
@property(nonatomic, nullable) UIBezierPath *path;

/** The animation duration for changes to the path of the selection indicator. */
@property(nonatomic, assign) CFTimeInterval indicatorPathAnimationDuration;

/** The timing function for animating changes to the path of the selection indicator. */
@property(nonatomic, strong, nonnull) CAMediaTimingFunction *indicatorPathTimingFunction;

@end

@interface MDCTabBarViewIndicatorView ()
/// View responsible for drawing the indicator's path.
@property(nonatomic, strong) MDCTabBarViewIndicatorShapeView *shapeView;
@end

@implementation MDCTabBarViewIndicatorView

- (instancetype)initWithFrame:(CGRect)frame {
  self = [super initWithFrame:frame];
  if (self) {
    [self commonMDCTabBarViewIndicatorViewInit];
  }
  return self;
}

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

#pragma mark - Public

- (void)applySelectionIndicatorAttributes:(MDCTabBarViewIndicatorAttributes *)attributes {
  self.shapeView.path = attributes.path;
}

- (CAMediaTimingFunction *)indicatorPathTimingFunction {
  return self.shapeView.indicatorPathTimingFunction;
}

- (void)setIndicatorPathTimingFunction:(CAMediaTimingFunction *)indicatorPathTimingFunction {
  self.shapeView.indicatorPathTimingFunction = indicatorPathTimingFunction;
}

- (CFTimeInterval)indicatorPathAnimationDuration {
  return self.shapeView.indicatorPathAnimationDuration;
}

- (void)setIndicatorPathAnimationDuration:(CFTimeInterval)indicatorPathAnimationDuration {
  self.shapeView.indicatorPathAnimationDuration = indicatorPathAnimationDuration;
}

#pragma mark - Private

- (void)commonMDCTabBarViewIndicatorViewInit {
  // Fill the indicator with the shape.
  _shapeView = [[MDCTabBarViewIndicatorShapeView alloc] initWithFrame:self.bounds];
  _shapeView.autoresizingMask = UIViewAutoresizingFlexibleWidth | UIViewAutoresizingFlexibleHeight;
  [self addSubview:_shapeView];
}

@end

#pragma mark -

@implementation MDCTabBarViewIndicatorShapeView

- (instancetype)initWithFrame:(CGRect)frame {
  self = [super initWithFrame:frame];
  if (self) {
    [self commonMDCTabBarViewIndicatorShapeViewInit];
  }
  return self;
}

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

- (void)commonMDCTabBarViewIndicatorShapeViewInit {
  _indicatorPathTimingFunction =
      [CAMediaTimingFunction functionWithName:kCAMediaTimingFunctionEaseInEaseOut];
  _indicatorPathAnimationDuration = 0.3;
}

- (UIBezierPath *)path {
  CAShapeLayer *shapeLayer = (CAShapeLayer *)self.layer;
  CGPathRef cgPath = shapeLayer.path;
  return cgPath ? [UIBezierPath bezierPathWithCGPath:cgPath] : nil;
}

- (void)setPath:(UIBezierPath *)path {
  CAShapeLayer *shapeLayer = (CAShapeLayer *)self.layer;
  shapeLayer.path = path.CGPath;
}

#pragma mark - CALayerDelegate

- (id<CAAction>)actionForLayer:(CALayer *)layer forKey:(NSString *)event {
  id<CAAction> action = [super actionForLayer:layer forKey:event];
  // Support implicit animation of paths.
  if ((!action || action == [NSNull null]) && (layer == self.layer) && [event isEqual:@"path"]) {
    CABasicAnimation *animation = [CABasicAnimation animationWithKeyPath:event];
    animation.duration = self.indicatorPathAnimationDuration;
    animation.timingFunction = self.indicatorPathTimingFunction;
    return animation;
  }
  return action;
}

#pragma mark - UIView

+ (Class)layerClass {
  return [CAShapeLayer class];
}

- (void)tintColorDidChange {
  [super tintColorDidChange];

  // Update layer fill color
  CAShapeLayer *shapeLayer = (CAShapeLayer *)self.layer;
  shapeLayer.fillColor = self.tintColor.CGColor;
}

@end