修改UIWebView的ua，加载webOffice的.PDF文件

//
修改ua
NSString* userAgent = [self.myWebView stringByEvaluatingJavaScriptFromString:@"navigator.userAgent"];
NSString *executableFile = [[[NSBundle
mainBundle]
infoDictionary]
objectForKey:(NSString *)kCFBundleExecutableKey];
NSString *version = [[[NSBundle mainBundle] infoDictionary] objectForKey:(NSString *)kCFBundleVersionKey];

//系统ua
NSString* hereUa = [NSString stringWithFormat:@"%@ %@/%@",
userAgent,
executableFile,version];
//
加载PDF的ua
NSString * webUa = @"Mozilla/5.0 (Macintosh; U; Intel Mac OS X 10_6_3; en-us) AppleWebKit/533.16
(KHTML, like Gecko) Version/5.0 Safari/533.16";
[[NSUserDefaults standardUserDefaults] registerDefaults:@{@"UserAgent" : webUa, @"User-Agent"
: hereUa}];

//===============================================================================================

NSURLRequest* request = [NSURLRequest requestWithURL:courceUrl];
NSString *lowerCaseString1 = [courseType lowercaseString];//转成小写
// 修改webView的request的ua
if ([lowerCaseString1 isEqualToString:@"pdf"]) {
[request valueForHTTPHeaderField:@"User-Agent"];
}else{
[request valueForHTTPHeaderField:@"UserAgent"];
}
[self.myWebView loadRequest:request];