iOS userAgent

User-Agent（用户代理）字符串是Web浏览器用于声明自身型号版本并随HTTP请求发送给Web服务器的字符串，在Web服务器上可以获取到该字符串。

在公司产品中，在userAgent中增加了NetType字段，用于标识客户端当前的网络环境。

• NetType/WIFI
• NetType/3G

web服务器端根据NetType类型加载不同分辨率的商品图片。我们只有两种，WIFI下高清图，非WIFI低分辨率图。

一、如何获取UserAgent

UIWebView方式：

• UIWebView *webView = [[UIWebView alloc] initWithFrame:CGRectZero];

• NSString *userAgent = [webView stringByEvaluatingJavaScriptFromString:@"navigator.userAgent"];

• DLog(@"userAgent :%@", userAgent);

WKWebView方式：

// 注意这个方法是异步的

• WKWebView *wkWebView = [[WKWebView alloc] initWithFrame:CGRectZero];
• [wkWebView evaluateJavaScript:@"navigator.userAgent" completionHandler:^(id result, NSError *error) { DLog(@"userAgent :%@", result); }];

二、如何修改UserAgent

方案一，修改全局UserAgent值（这里是在原有基础上拼接自定义的字符串）

• - (BOOL)application:(UIApplication *)application didFinishLaunchingWithOptions:(NSDictionary *)launchOptions {
• UIWebView *webView = [[UIWebView alloc] initWithFrame:CGRectZero];
• NSString *userAgent = [webView stringByEvaluatingJavaScriptFromString:@"navigator.userAgent"];
• NSString *newUserAgent = [userAgent stringByAppendingString:@" native_iOS"];
• //自定义需要拼接的字符串 NSDictionary *dictionary = [NSDictionary dictionaryWithObjectsAndKeys:newUserAgent, @"UserAgent", nil];
• [[NSUserDefaults standardUserDefaults] registerDefaults:dictionary]; }

方案二，自定义UserAgent值

• WKWebView *wkWebView = [[WKWebView alloc] initWithFrame:self.view.bounds];
• [self.view addSubview: wkWebView];
• NSString *customUserAgent = @"native_iOS";
• [[NSUserDefaults standardUserDefaults] registerDefaults:@{@"UserAgent":customUserAgent}];
• [[NSUserDefaults standardUserDefaults] synchronize];
• [self.wkWebView setCustomUserAgent:customUserAgent];
• NSURL *url = [NSURL URLWithString:self.strUrl];
• NSURLRequest *request = [NSURLRequest requestWithURL:url cachePolicy:NSURLRequestUseProtocolCachePolicy timeoutInterval:10.f];
• [self.wkWebView loadRequest:request];

方案三

• self.wkWebView = [[WKWebView alloc] initWithFrame:self.view.bounds];
• __weak typeof(self) weakSelf = self;
• [self.wkWebView evaluateJavaScript:@"navigator.userAgent" completionHandler:^(id result, NSError *error) {
• __strong typeof(weakSelf) strongSelf = weakSelf;
• NSString *userAgent = result;
• NSString *newUserAgent = [userAgent stringByAppendingString:@" native_iOS"];
• NSDictionary *dictionary = [NSDictionary dictionaryWithObjectsAndKeys:newUserAgent, @"UserAgent", nil];
• [[NSUserDefaults standardUserDefaults] registerDefaults:dictionary];
• [[NSUserDefaults standardUserDefaults] synchronize];
• [strongSelf.wkWebView setCustomUserAgent:customUserAgent];
• strongSelf.wkWebView = [[WKWebView alloc] initWithFrame:strongSelf.view.bounds];
• }];
• [self.wkWebView loadRequest:request];