@interface ViewController ()<UIWebViewDelegate>  @property (weak, nonatomic) IBOutlet UIBarButtonItem *backItem;  @property (weak, nonatomic) IBOutlet UIBarButtonItem *forwardItem;  @property(nonatomic,weak)UIWebView * webView;  - (IBAction)back;  - (IBAction)forward;    @end    @implementation ViewController    - (void)viewDidLoad {      [super viewDidLoad];                  //1.创建webView      UIWebView * webView = [[UIWebView alloc]init];      webView.frame = self.view.bounds;      self.webView = webView;      [self.view addSubview:webView];      //设置代理      webView.delegate = self;                  //2.加载请求      //加载的三种方式，加载三种数据            //《1》加载url请求  //        NSURL * url = [[NSBundle mainBundle]URLForResource:@"login" withExtension:@"html"];  //        NSURLRequest * request = [NSURLRequest requestWithURL:url];  //        [webView loadRequest:request];            //《2》加载html（用于显示传递过来的内容，因为loadHTMLString传递的是什么，就显示什么）(这种方式加载的网页，不能回退)  //    NSString * path = [[NSBundle mainBundle]pathForResource:@"login.html" ofType:nil];  //    NSString * string = [NSString stringWithContentsOfFile:path encoding:NSUTF8StringEncoding error:nil];  //    NSLog(@"----%@", string);  //    [webView loadHTMLString:string baseURL:nil];                        //《3》加载data数据（可以加载图片，word，pdf等）（这个方法加载的也不能回退）            //获取路径      NSString * path = [[NSBundle mainBundle]pathForResource:@"hell" ofType:@"pdf"];      //获取mimetype      NSURL * url = [NSURL fileURLWithPath:path];//不要使用urlWithString方法      NSURLRequest * request = [NSURLRequest requestWithURL:url];      NSURLResponse  * rest = nil;      [NSURLConnection  sendSynchronousRequest:request returningResponse:&rest error:nil];//因为需要使用这个返回值，所以使用同步方法      //加载      NSData * data = [NSData dataWithContentsOfFile:path];      [webView loadData:data MIMEType:rest.MIMEType textEncodingName:@"utf8"baseURL:nil];      NSLog(@"MIMEType-----%@",rest.MIMEType);      NSLog(@"%ld",data.length);                    }      - (IBAction)back{      [self.webView goBack];//不使用dismiss方法,因为跳转的不是控制器        }    - (IBAction)forward {      [self.webView goForward];//前进  }        #pragma mark - UIWebViewDelegate(四个代理方法)  - (void)webViewDidStartLoad:(UIWebView *)webView{  //    NSLog(@"webViewDidStartLoad");        }  - (void)webViewDidFinishLoad:(UIWebView *)webView{      //    if ([webView canGoBack]) {//先判断这个页面有没有返回功能      //        self.backItem.enabled = YES;      //    }else{      //    self.backItem.enabled = NO;      //    }            //简便写法      NSLog(@"########%i", [webView canGoBack]);      self.backItem.enabled = [webView canGoBack];      self.forwardItem.enabled = [webView canGoForward];        }  - (void)webView:(UIWebView *)webView didFailLoadWithError:(NSError *)error{  //    NSLog(@"didFailLoadWithError");  }      - (BOOL)webView:(UIWebView *)webView shouldStartLoadWithRequest:(NSURLRequest *)request navigationType:(UIWebViewNavigationType)navigationType{      //URL      //"http://www.baidu.com/"      //协议头://主机名//路径            //过滤掉还有baidu的url  //    NSString * path = request.URL.absoluteString;//注意不是URL.path这个方法，这个方法返回的是“/”  //    NSInteger location = [path rangeOfString:@"baidu"].location;  //    if (location != NSNotFound) {  //        return NO;  //    }            NSLog(@"%@", request.URL.absoluteString);      return YES;        }    @end