iOS中UIWebView网页加载组件的基础及使用技巧实例

基本用法示例

- (void)viewDidLoad
{
  [super viewDidLoad];
  // Do any additional setup after loading the view.

  UIWebView * webView = [[UIWebView alloc]initWithFrame:CGRectMake(0, 20, ScreenWidth, ScreenHeight-20)];
  // 自动队页面进行缩放以适应屏幕
  webView.scalesPageToFit = YES;
  webView.userInteractionEnabled = YES;
  webView.opaque = YES;

  [self.view addSubview:webView];

  NSURL * url = [NSURL URLWithString:@"http://www.youku.com"];
  NSURLRequest * request = [NSURLRequest requestWithURL:url];
  [webView loadRequest:request];
//  NSString * myHT = @"优酷";
//  [webView loadHTMLString:myHT baseURL:url];
/*
  [webView goBack];    // 返回
  [webView goForward];   // 前往
  [webView reload];
  [webView stopLoading];
 */
  webView.delegate = self;

  //移除滚动后的外边阴影
  UIScrollView *scrollView = webView.scrollView;
  for (int i = 0; i < scrollView.subviews.count ; i++) {
    UIView *view = [scrollView.subviews objectAtIndex:i];
    if ([view isKindOfClass:[UIImageView class]]) {
      view.hidden = YES ;
    }
  }
}

#pragma mark - UIWebViewDelegate
- (BOOL)webView:(UIWebView *)webView shouldStartLoadWithRequest:(NSURLRequest *)request navigationType:(UIWebViewNavigationType)navigationType{

  /**
   * typedef NS_ENUM(NSInteger, UIWebViewNavigationType) {
   * UIWebViewNavigationTypeLinkClicked,
   * UIWebViewNavigationTypeFormSubmitted,
   * UIWebViewNavigationTypeBackForward,
   * UIWebViewNavigationTypeReload,
   * UIWebViewNavigationTypeFormResubmitted,
   * UIWebViewNavigationTypeOther
   };
   */

  NSLOG_FUNCTION;

  return YES;
}

// 开始加载
- (void)webViewDidStartLoad:(UIWebView *)webView{

  NSLOG_FUNCTION;

}

// 完成加载
- (void)webViewDidFinishLoad:(UIWebView *)webView{

  NSLOG_FUNCTION;

}

// 加载失败,弹出错误提示
- (void)webView:(UIWebView *)webView didFailLoadWithError:(NSError *)error{

  UIAlertView *alterview = [[UIAlertView alloc] initWithTitle:@"" message:[error localizedDescription]
                            delegate:nil cancelButtonTitle:nil otherButtonTitles:@"OK", nil];
  [alterview show];
  [alterview release];
  NSLOG_FUNCTION;

}

以下是关于它的一些使用技巧：

1.让网页适应手机屏幕宽度

如果用UIWebView显示一些pc站的网页，会发现网页会超出屏幕，显得很不好看，这时可以在webViewDidFinishLoad这个代理里面通过js添加一个meta：

- (void)webViewDidFinishLoad:(UIWebView *)webView

{

  NSString *meta = [NSString stringWithFormat:@"document.getElementsByName(\"viewport\")[0].content = \"width=%f, initial-scale=1.0, minimum-scale=1.0, maximum-scale=1.0, user-scalable=no\"", IPHONE_WIDTH];

  [webView stringByEvaluatingJavaScriptFromString:meta];

}

注意：使用这个方法时要把UIWebView的scalesPageToFit设成NO

webView.scalesPageToFit = NO;

2.为网页中的图片添加点击事件，当点击图片时放大查看

思路是给每一个img标签添加onclick事件，在事件中把img的src属性封装成一个特殊的url，然后进行拦截

如果是通过loadHTMLString去加载网页的话，可以执行下面一句进行替换：

    html = [html stringByReplacingOccurrencesOfString:@"<img " withString:@"<img onclick=\"window.location.href=('http://src.'+this.src);\" "];

如果是通过loadRequest，那就要再webViewDidFinishLoad中执行以下JS：

  NSString *js = @"var imgs = document.getElementsByTagName(\"img\");"

  "for(var i=0;i<imgs.length;i++){"

  "  var img = imgs[i];"

  "  img.onclick=function(){window.location.href=('http://src.'+this.src);}"

  "}";

  [webView stringByEvaluatingJavaScriptFromString:js];

然后通过webview的代理方法去拦截，拿到图片的url，之后就可以做各种处理了

- (BOOL)webView:(UIWebView *)webView shouldStartLoadWithRequest:(NSURLRequest *)request navigationType:(UIWebViewNavigationType)navigationType

{

  NSString *url = request.URL.absoluteString;

  if ([url hasPrefix:@"http://src."])

  {

    url = [url stringByReplacingOccurrencesOfString:@"http://src." withString:@""];

    // Do something..

    return NO;

  }

  return YES;

}

3.为UIWebView添加一个跟随网页滚动的页头

UIWebView里包含一个scrollview，可以向scrollview里添加一个页头以达到跟随网页滚动的效果

CGFloat headerHeight = 36.0f;

// 注意：y坐标必须是负数，IPHONE_WIDTH是屏幕宽度

UIView *headerView = [[UIView alloc] initWithFrame:CGRectMake(0, -headerHeight, IPHONE_WIDTH, headerHeight)];

[_webView.scrollView addSubview:_headerView];

// 修改webView的scrollView的contentInset，让顶部留出一点空间

UIEdgeInsets edgeInset = _webView.scrollView.contentInset;

_webView.scrollView.contentInset = UIEdgeInsetsMake(headerView.frameHeight, edgeInset.left, edgeInset.bottom, edgeInset.right);