iOS预加载Web页面方案

khan7923 4年前
   <h2><strong>iOS预加载Web页面方案</strong></h2>    <p>可以预加载多个网址,然后在离线状态去显示那几个网址,看看是不是都完全缓存下来了。</p>    <h2><strong>使用方法</strong></h2>    <p>在需要开启预加载的地方创建</p>    <pre>  <code class="language-objectivec">self.sCache = [STMURLCache create:^(STMURLCacheMk *mk) {      mk.whiteListsHost(whiteLists).whiteUserAgent(@"starming");  }];</code></pre>    <p>这里是所有可设置项目,默认设置可以查看 model 的 get 方法</p>    <pre>  <code class="language-objectivec">- (STMURLCacheMk *(^)(NSUInteger)) memoryCapacity;   //内存容量  - (STMURLCacheMk *(^)(NSUInteger)) diskCapacity;     //本地存储容量  - (STMURLCacheMk *(^)(NSUInteger)) cacheTime;        //缓存时间  - (STMURLCacheMk *(^)(NSString *)) subDirectory;     //子目录  - (STMURLCacheMk *(^)(BOOL)) isDownloadMode;         //是否启动下载模式  - (STMURLCacheMk *(^)(NSArray *)) whiteListsHost;    //域名白名单  - (STMURLCacheMk *(^)(NSString *)) whiteUserAgent;   //WebView的user-agent白名单    - (STMURLCacheMk *(^)(NSString *)) addHostWhiteList;        //添加一个域名白名单  - (STMURLCacheMk *(^)(NSString *)) addRequestUrlWhiteList;  //添加请求白名单    //NSURLProtocol相关设置  - (STMURLCacheMk *(^)(BOOL)) isUsingURLProtocol; //是否使用NSURLProtocol,默认使用NSURLCache</code></pre>    <p>也可以随时更新这些设置项</p>    <pre>  <code class="language-objectivec">[self.sCache update:^(STMURLCacheMk *mk) {      mk.isDownloadMode(YES);  }];</code></pre>    <p>预加载名单可以按照整个 web 页面请求进行预加载</p>    <pre>  <code class="language-objectivec">[self.sCache preLoadByWebViewWithUrls:@[@"http://www.v2ex.com",@"http://www.github.com"];</code></pre>    <p>如果需要按照单个资源列表进行预加载可以使用 preLoadByRequestWithUrls 这个方法。</p>    <h2><strong>白名单设置</strong></h2>    <p>对于只希望缓存特定域名或者地址的可以通过白名单进行设置,可以在创建时进行设置或者更新时设置。</p>    <pre>  <code class="language-objectivec">NSString *whiteListStr = @"www.starming.com|www.github.com|www.v2ex.com|www.baidu.com";  NSMutableArray *whiteLists = [NSMutableArray arrayWithArray:[whiteListStr componentsSeparatedByString:@"|"]];  self.sCache = [STMURLCache create:^(STMURLCacheMk *mk) {      mk.whiteListsHost(whiteLists).whiteUserAgent(@"starming");  }];</code></pre>    <p>这里的 <em>whiteUserAgent</em> 的设置会设置 webview 的 UserAgent,这样能够让webview以外的网络请求被过滤掉。</p>    <h2><strong>基本加载缓存实现原理</strong></h2>    <p>创建 STMURLCache 后设置 NSURLCache 的 URLCache ,在 cachedResponseForRequest 方法中获取 NSURLRequest 判断白名单,检验是否有与之对应的 Cache ,有就使用本地数据返回 NSCachedURLResponse ,没有就通过网络获取数据数据缓存。 STMURLCache 对象释放时将 NSURLCache 设置为不缓存,表示这次预加载完成不需要再缓存。当缓存空间超出设置大小会将其清空。</p>    <p>使用 <em>NSURLProtocol</em> 这种原理基本类似。</p>    <h2><strong>白名单实现原理</strong></h2>    <p>创建域名列表设置项 whiteListsHost 和 userAgent 设置项,在创建和更新时对其进行设置。在网络请求开始通过设置项进行过滤。具体实现如下</p>    <pre>  <code class="language-objectivec">//对于域名白名单的过滤  if (self.mk.cModel.whiteListsHost.count > 0) {      id isExist = [self.mk.cModel.whiteListsHost objectForKey:[self hostFromRequest:request]];      if (!isExist) {          return nil;      }  }  //User-Agent来过滤  if (self.mk.cModel.whiteUserAgent.length > 0) {      NSString *uAgent = [request.allHTTPHeaderFields objectForKey:@"User-Agent"];      if (uAgent) {          if (![uAgent hasSuffix:self.mk.cModel.whiteUserAgent]) {              return nil;          }      }  }</code></pre>    <h2><strong>具体缓存实现</strong></h2>    <p>缓存的实现有两种,一种是 <em>NSURLCache</em> 另一种是 <em>NSURLProtocol</em> , <em>STMURLCache</em> 同时支持了这两种,通过 <em>STMURLCacheModel</em> 里的 <em>isUsingURLProtocol</em> 设置项来选择使用哪个。</p>    <h3><strong>NSURLCache的实现</strong></h3>    <p>没有缓存的 request 会对其进行请求将获取数据按照hash地址存两份于本地,一份是数据,一份记录时间和类型,时间记录可以用于判断失效时间。对于判断是否有缓存可以根据请求地址对应的文件进行判断。具体实现如下:</p>    <pre>  <code class="language-objectivec">- (NSCachedURLResponse *)localCacheResponeWithRequest:(NSURLRequest *)request {      __block NSCachedURLResponse *cachedResponse = nil;      NSString *filePath = [self filePathFromRequest:request isInfo:NO];      NSString *otherInfoPath = [self filePathFromRequest:request isInfo:YES];      NSDate *date = [NSDate date];      NSFileManager *fm = [NSFileManager defaultManager];      if ([fm fileExistsAtPath:filePath]) {          //有缓存文件的情况          BOOL expire = false;          NSDictionary *otherInfo = [NSDictionary dictionaryWithContentsOfFile:otherInfoPath];          if (self.cacheTime > 0) {              NSInteger createTime = [[otherInfo objectForKey:@"time"] integerValue];              if (createTime + self.cacheTime < [date timeIntervalSince1970]) {                  expire = true;              }          }          if (expire == false) {              //从缓存里读取数据              NSData *data = [NSData dataWithContentsOfFile:filePath];              NSURLResponse *response = [[NSURLResponse alloc] initWithURL:request.URL MIMEType:[otherInfo objectForKey:@"MIMEType"] expectedContentLength:data.length textEncodingName:[otherInfo objectForKey:@"textEncodingName"]];              NSCachedURLResponse *cachedResponse = [[NSCachedURLResponse alloc] initWithResponse:response data:data];              return cachedResponse;          } else {              //cache失效了              [fm removeItemAtPath:filePath error:nil];      //清除缓存data              [fm removeItemAtPath:otherInfoPath error:nil]; //清除缓存其它信息              return nil;          }      } else {          //从网络读取          self.isSavedOnDisk = NO;          id isExist = [self.responseDic objectForKey:request.URL.absoluteString];          if (isExist == nil) {              [self.responseDic setValue:[NSNumber numberWithBool:TRUE] forKey:request.URL.absoluteString];              NSURLSession *session = [NSURLSession sharedSession];              NSURLSessionDataTask *task = [session dataTaskWithRequest:request completionHandler:^(NSData * _Nullable data, NSURLResponse * _Nullable response, NSError * _Nullable error) {                  if (error) {                      cachedResponse = nil;                  } else {                      NSDictionary *dic = [NSDictionary dictionaryWithObjectsAndKeys:[NSString stringWithFormat:@"%f",[date timeIntervalSince1970]],@"time",response.MIMEType,@"MIMEType",response.textEncodingName,@"textEncodingName", nil];                      BOOL resultO = [dic writeToFile:otherInfoPath atomically:YES];                      BOOL result = [data writeToFile:filePath atomically:YES];                      if (resultO == NO || result == NO) {                      } else {                      }                      cachedResponse = [[NSCachedURLResponse alloc] initWithResponse:response data:data];                  }              }];              [task resume];              return cachedResponse;          }          return nil;      }  }</code></pre>    <h3><strong>NSURLProtocol的实现</strong></h3>    <p>在设置配置项和更新配置项时需要创建一个 <em>STMURLCacheModel</em> 的单例来进行设置和更新配置项给 NSURLProtocol 的实现来使用。通过 isUsingURLProtocol 设置项区分, NSURLProtocol 是通过registerClass方式将protocol实现的进行注册。</p>    <pre>  <code class="language-objectivec">- (STMURLCache *)configWithMk {        self.mk.cModel.isSavedOnDisk = YES;        if (self.mk.cModel.isUsingURLProtocol) {          STMURLCacheModel *sModel = [STMURLCacheModel shareInstance];          sModel.cacheTime = self.mk.cModel.cacheTime;          sModel.diskCapacity = self.mk.cModel.diskCapacity;          sModel.diskPath = self.mk.cModel.diskPath;          sModel.cacheFolder = self.mk.cModel.cacheFolder;          sModel.subDirectory = self.mk.cModel.subDirectory;          sModel.whiteUserAgent = self.mk.cModel.whiteUserAgent;          sModel.whiteListsHost = self.mk.cModel.whiteListsHost;          [NSURLProtocol registerClass:[STMURLProtocol class]];      } else {          [NSURLCache setSharedURLCache:self];      }      return self;  }</code></pre>    <p>关闭时两者也是不同的,通过设置项进行区分</p>    <pre>  <code class="language-objectivec">- (void)stop {      if (self.mk.cModel.isUsingURLProtocol) {          [NSURLProtocol unregisterClass:[STMURLProtocol class]];      } else {          NSURLCache *c = [[NSURLCache alloc] initWithMemoryCapacity:0 diskCapacity:0 diskPath:nil];          [NSURLCache setSharedURLCache:c];      }      [self.mk.cModel checkCapacity];  }</code></pre>    <p>白名单处理还有读取缓存和前者都类似,但是在缓存Data时 <em>NSURLCached</em> 的方案里是通过发起一次新的请求来获取数据,而 <em>NSURLProtocol</em> 在 <em>NSURLConnection</em> 的 Delegate 里可以获取到,少了一次网络的请求,这里需要注意的是在 - (void) connection:(NSURLConnection <em>)connection didReceiveData:(NSData</em> )data 每次从这个回调里获取的数据不是完整的,要在 - (void) connectionDidFinishLoading:(NSURLConnection *)connection 这个会调里将分段数据拼接成完整的数据保存下来。具体完整的代码实现可以看 STMURLProtocol 里的代码实现。</p>    <h2><strong>后记</strong></h2>    <p>通过 <em>map</em> 网络请求可以缓存请求,也可以 <em>mock</em> 接口请求进行测试。</p>    <p> </p>    <p>来自:http://www.cocoachina.com/ios/20161130/18230.html</p>    <p> </p>