一、瘦身技术大图
二、On-Demand Resources 简介
将其保存管理在苹果的服务器，按需使用资源、优化包体积，实现更小的应用程序。ODR 的好处：
- 应用体积更小，下载更快，提升初次启动速度
- 资源会在后台下载
- 操作系统将会在磁盘资源不够的时候清理 ODR
三、实现
3.1、创建标签
标签的理想大小小于或等于64 MB。这种尺寸在下载速度和本地存储空间之间提供了良好的平衡，以便在设备的本地存储空间不足时进行清理。
- Initial install tags：初始安装标签，资源与应用程序同时下载；
- Prefetch tag order.：预取标签顺序，安装应用程序后，资源开始下载；
- Dowloaded only on demand：仅按需下载。当应用程序要求时，标签会下载；
3.2、pod组建引用
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| s.on_demand_resources = { 'Tag1' => 'file1.png' } s.on_demand_resources = { 'Tag1' => 'file1.png', 'file2.png' } s.on_demand_resources = { 'Tag1' => { :paths => 'file1.png', 'file2.png', :category => :download_on_demand } } s.on_demand_resources = { 'Tag1' => { :paths => 'file1.png', 'file2.png', :category => :initial_install } } |
3.3、访问和下载资源
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| - (NSBundleResourceRequest *)requestOdrWithTags:(NSSet<NSString *> *)tags { NSBundleResourceRequest *request = \[NSBundleResourceRequest alloc initWithTags:tags]; /// 检查设备上是否已有标签 request conditionallyBeginAccessingResourcesWithCompletionHandler:\^(BOOL resourcesAvailable) { if (!resourcesAvailable) { /// 资源不在本地 \[request beginAccessingResourcesWithCompletionHandler:\^(NSError \* _Nullable error) { if (error) { /// 下载失败 \[self failRetryWithTags:tags; } else { /// 下载成功 self.retryDelay = 0; } }]; } else { /// 资源已存在 self.retryDelay = 0; } }]; return request; } |
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| @interface IMYOdrManager () /// 持有 NSBundleResourceRequest，资源才会被使用，要不然会被释放 /// 每个NSBundleResourceRequest 对象只能用于一个请求访问/结束访问周期。 @property (nonatomic, strong) NSBundleResourceRequest *request; @end @implementation IMYOdrManager @synthesize tagName; IMY_KYLIN_FUNC_LAUNCHED_ASYNC { NSSet *set = NSSet setWithObject:@"IMYLevel1"; \[IMYOdrManager sharedInstance reloadOdrWithTags:set]; } + (instancetype)sharedInstance { static id instance; static dispatch_once_t onceToken; dispatch_once(&onceToken, ^{ instance = self new; }); return instance; } - (instancetype)init { if (self = super init) { self addObserver; } return self; } #pragma mark - public - (void)reloadOdrWithTags:(NSSet *)set { self.tagName = set; self reloadOdr; } - (void)reloadOdr { if (self.tagName.count > 0) { self.request = \[IMYOdrDownloadManager new requestOdrWithTags:self.tagName]; // 设置优先级 between 0.0 and 1.0 self.request.loadingPriority = 1.0; } } #pragma mark - private - (void)addObserver { /// 低空位警告 @weakify(self); \[\[\[\[NSNotificationCenter defaultCenter rac_addObserverForName:NSBundleResourceRequestLowDiskSpaceNotification object:nil] deliverOnMainThread] takeUntil:self.rac_willDeallocSignal] subscribeNext:^(NSNotification *notify) { @strongify(self); self.request endAccessingResources; }]; } @end |
3.4、一些额外方法
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| /// 暂停当前下载 - (void)pauseOdr { self.request.progress pause; } /// 恢复当前下载 - (void)resumeOdr { self.request.progress resume; } /// 取消当前下载 - (void)cancelOdr { self.request.progress cancel; } |
3.5、运行后的效果
3.6、通常的设计原则
- 必要时可用
- 下载期间影响最小
- 对应用程序内存的影响最小
四、参考文献