iOS预加载Web页面方案
khan7923
8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>