我的应用是一个电子阅读器,用于在 iPhone/iPad 上阅读书籍。用户可以选择下载我们在设备上保存为 .epub 文件(压缩内容)的图书 - 这样可以在离线时查看图书。页面内容为html。
有些 Assets (如视频)不在此 .epub 内容中。当用户导航到这样的页面时,我必须检测不在 .ePub 中的外部 Assets ,并显示一个简单的占位符,其中包含文本“此内容在离线时不可用”。
这些视频可以嵌入到 iFrame html 标签或对象标签中。
现在我们有一个继承自 NSURLProtocol 抽象类的类,我正在使用它来处理这个需求。我有这 3 种方法的实现:
+ (BOOL) canInitWithRequest:(NSURLRequest *)request
- (void)startLoading
- (void) sendResponse:(NSData *)data mimetype:(NSString *)mimetype url:(NSURL *)url
我现在的问题是我有一个简单的 .png 显示“离线时此内容不可用”,但它很难看,因为有时 iFrame 的区域小于图像。我如何缩放它以适应?或者有更好的方法吗?它不一定是图像,只要我可以显示此内容不可用的消息即可。我当前在 startLoading 方法中的代码:
- (void) startLoading
{
…
NSString *bundlePath = [NSString stringWithFormat:@"%@/%@",[[NSBundle mainBundle] bundlePath],@"PxeReaderResources.bundle"];
NSString *pathToPlaceholder = [NSString stringWithFormat:@"%@/%@",bundlePath,@"OfflinePlaceholder.png"]; //my placeholder image
NSLog(@"Path to placeholder is: %@", pathToPlaceholder);
data = [[NSFileManager defaultManager] contentsAtPath:pathToPlaceholder];
…
[self sendResponse:data mimetype:@"application/octet-stream" url:self.request.URL];
}
- (void) sendResponse:(NSData *)data mimetype:(NSString *)mimetype url:(NSURL *)url
{
NSDictionary *headers = @{@"Content-Type" : mimetype, @"Access-Control-Allow-Origin" : @"*", @"Cache-control" : @"no-cache"};
NSHTTPURLResponse *response = [[NSHTTPURLResponse alloc] initWithURL:url statusCode:200 HTTPVersion:@"HTTP/1.1" headerFields:headers];
[self.client URLProtocol:self didReceiveResponse:response cacheStoragePolicy:NSURLCacheStorageNotAllowed];
[self.client URLProtocol:self didLoadData:data];
[self.client URLProtocolDidFinishLoading:self];
}
感谢您的任何建议。
最佳答案
我能够发送一个简单的自定义 html div 标签来代替外部 Assets 。这是代码 - 希望这会对某人有所帮助。 注意:所有这些代码都在我继承自 NSURLProtocol 的自定义类中
#define EXTERNAL_REQUEST_KEY @"ExternalRequest"
+ (BOOL) canInitWithRequest:(NSURLRequest *)request
{
NSString* filePath = [[PxePlayer sharedInstance] getBaseURL]; //gets base path to the epub zipped folder
if ([Reachability isReachable])
{
return filePath != nil && [@"file" caseInsensitiveCompare:request.URL.scheme] == NSOrderedSame;
}
else
{
if ([request.URL.scheme isEqualToString:@"https"] || [request.URL.scheme isEqualToString:@"http"]) //these schemes won't work if offline
{
[NSURLProtocol setProperty:@YES forKey:EXTERNAL_REQUEST_KEY inRequest:(NSMutableURLRequest*)request]; //marking those request so that we will only provide placeholder for these requests
}
return filePath != nil && ([@"file" caseInsensitiveCompare:request.URL.scheme] == NSOrderedSame ||
[@"https" caseInsensitiveCompare:request.URL.scheme] == NSOrderedSame ||
[@"http" caseInsensitiveCompare:request.URL.scheme] == NSOrderedSame);
}
}
- (void) startLoading
{
...
if ([NSURLProtocol propertyForKey:EXTERNAL_REQUEST_KEY inRequest:self.request])
{
custMimeType = @"text/html";
data = [self prepareDataForPlaceholderForExternalAsset];
}
...
if (data)
{
//Now ready to send the placeholder as custom response
[self sendResponse:data mimetype:custMimeType url:self.request.URL];
}
}
//method to create a simple div tag as NSData
- (NSData*) prepareDataForPlaceholderForExternalAsset
{
NSString *placeholder =
@"<div style=\"background-color:#efefef; border:1px solid #999999; text-align:center; width:100%; height:100%\"> \
<font font-family=\"Helvetica Neue\" font-weight=\"Medium\" size=\"5\" color=\"#b3b3b3\"> \
<div style=\"display:inline-block; margin-top:5%\"> \
This content is unavailable when offline or printing \
</div> \
</font> \
</div>";
return [placeholder dataUsingEncoding:NSUTF8StringEncoding];
}
- (void) sendResponse:(NSData *)data mimetype:(NSString *)mimetype url:(NSURL *)url
{
NSDictionary *headers = @{@"Content-Type" : mimetype, @"Access-Control-Allow-Origin" : @"*", @"Cache-control" : @"no-cache"};
NSHTTPURLResponse *response = [[NSHTTPURLResponse alloc] initWithURL:url statusCode:200 HTTPVersion:@"HTTP/1.1" headerFields:headers];
[self.client URLProtocol:self didReceiveResponse:response cacheStoragePolicy:NSURLCacheStorageNotAllowed];
[self.client URLProtocol:self didLoadData:data];
[self.client URLProtocolDidFinishLoading:self];
}
关于ios - UIWebView/NSURLProtocol - 离线时不可访问的外部 Assets 的占位符,我们在Stack Overflow上找到一个类似的问题: https://stackoverflow.com/questions/32635605/