设置webView 的 夜间模式

if (YES == [[NSUserDefaults standardUserDefaults]boolForKey:@"isNight"]) {

        [self.web stringByEvaluatingJavaScriptFromString:@"document.getElementsByTagName('body')[0].style.background='#BABABA'"];

       

       

    } else {

        [self.web stringByEvaluatingJavaScriptFromString:@"document.getElementsByTagName('body')[0].style.background='#FFFFFF'"];

    }

注 : 放在 - (void)webViewDidFinishLoad:(UIWebView *)webView 方法里