作为一名iOS工程师，深知复杂动画的痛苦，下面我们来介绍下Lottie来解决日常的动画难题。
Lottie的简单介绍：
- 使用Lottie开发的流程是： 设计师在AE中设计完成你的动画，通过bodymoving插件导出纪录动画信息的JSON文件，然后开发人员使用 Lottie 的Android，iOS，React Native apps开源动画库读取这份JSON文件, 解析动画结构和参数信息并渲染。
Lottie的优点：
- 设计即所见: 设计师用AE设计好动画后直接导出Json文件，Lottie 解析Json文件后调Core Animation的API绘制渲染。还原度更好，开发成本更低。
- 跨平台: 支持iOS、Android、React Native。
- 性能：Lottie对于从AE导出的Json文件，用Core Animation做矢量动画, 性能较佳。Lottie 对解析后的数据模型有内存缓存。但是对多图片帧动画，性能比较差。
支持动画属性多：比起脸书的Keyframes，Lottie支持了更多AE动画属性，比如Mask, Trim Paths,Stroke (shape layer)等。
- 包大小，相比动辄上百K的帧动画，Json文件包大小很小。有图片资源的情况下，同一张图片也可以被多个图层复用，而且运行时内存中只有一个UIImage对象（iOS）。
Lottie在iOS中的使用
- pod 'lottie-ios' 使用cocoaPods来加载Lottie。
- 在使用的界面添加头文件#import <Lottie/Lottie.h>
- 简单的使用介绍（要想深入学习，还需要自己点击进入源代码中去深究每一个方法和属性，在此就不一一列举了）
LOTAnimationView * animation = [LOTAnimationView animationNamed:@"HappyBirthday"];
animation.loopAnimation = YES; //是否是循环播放
animation.frame = self.view.bounds;
[self.view addSubview:animation];
animation.backgroundColor = [UIColor whiteColor];
[animation playWithCompletion:^(BOOL animationFinished) {
//播放完成，循环播放则不进入此方法
}];
//可以以动画为北京来添加子控件
UILabel * newV = [[UILabel alloc]initWithFrame:CGRectMake(100,100,200,100)];
newV.backgroundColor = [UIColor clearColor];
newV.textColor = [UIColor blackColor];
newV.text = @"Lottie的使用教程";
[animation addSubview:newV];
另外的创建方法
/// Load animation by name from the default bundle, Images are also loaded from the bundle
+ (nonnull instancetype)animationNamed:(nonnull NSString *)animationName NS_SWIFT_NAME(init(name:));
/// Loads animation by name from specified bundle, Images are also loaded from the bundle
+ (nonnull instancetype)animationNamed:(nonnull NSString *)animationName inBundle:(nonnull NSBundle *)bundle NS_SWIFT_NAME(init(name:bundle:));
/// Creates an animation from the deserialized JSON Dictionary
+ (nonnull instancetype)animationFromJSON:(nonnull NSDictionary *)animationJSON NS_SWIFT_NAME(init(json:));
/// Loads an animation from a specific file path. WARNING Do not use a web URL for file path.
+ (nonnull instancetype)animationWithFilePath:(nonnull NSString *)filePath NS_SWIFT_NAME(init(filePath:));
/// Creates an animation from the deserialized JSON Dictionary, images are loaded from the specified bundle
+ (nonnull instancetype)animationFromJSON:(nullable NSDictionary *)animationJSON inBundle:(nullable NSBundle *)bundle NS_SWIFT_NAME(init(json:bundle:));
/// Creates an animation from the LOTComposition, images are loaded from the specified bundle
- (nonnull instancetype)initWithModel:(nullable LOTComposition *)model inBundle:(nullable NSBundle *)bundle;
/// Loads animation asynchrounously from the specified URL
- (nonnull instancetype)initWithContentsOfURL:(nonnull NSURL *)url;
LOTAnimationView的属性
/// Flag is YES when the animation is playing
@property (nonatomic, readonly) BOOL isAnimationPlaying;
/// Tells the animation to loop indefinitely.
@property (nonatomic, assign) BOOL loopAnimation;
/// The animation will play forward and then backwards if loopAnimation is also YES
@property (nonatomic, assign) BOOL autoReverseAnimation;
/// Sets a progress from 0 - 1 of the animation. If the animation is playing it will stop and the compeltion block will be called.
/// The current progress of the animation in absolute time.
/// e.g. a value of 0.75 always represents the same point in the animation, regardless of positive
/// or negative speed.
@property (nonatomic, assign) CGFloat animationProgress;
/// Sets the speed of the animation. Accepts a negative value for reversing animation.
@property (nonatomic, assign) CGFloat animationSpeed;
/// Read only of the duration in seconds of the animation at speed of 1
@property (nonatomic, readonly) CGFloat animationDuration;
/// Enables or disables caching of the backing animation model. Defaults to YES
@property (nonatomic, assign) BOOL cacheEnable;
/// Sets a completion block to call when the animation has completed
@property (nonatomic, copy, nullable) LOTAnimationCompletionBlock completionBlock;
/// Set the amimation data
@property (nonatomic, strong, nullable) LOTComposition *sceneModel;
- 简单应用的场景：(1)App的动画引导页。(2)一些特定的动画界面。(3)来作为Tabbar来使用。
- 这里来介绍下作为Tabbar的使用gitHub上原作者
- Lottie动画资源网站
- 后续有新的学习会更新的。
