1、使用UIWebView加载网页

运行XCode 4.3，新建一个Single View Application，命名为WebViewDemo。

2、加载WebView

在ViewController.h添加WebView成员变量和在ViewController.m添加实现

[cpp] view plaincopyprint?

#import <UIKit/UIKit.h>   

  

@interface ViewController : UIViewController  

{  

    UIWebView *webView;  

}  

@end  

#import <UIKit/UIKit.h>@interface ViewController : UIViewController {UIWebView *webView; } @end [cpp] view plaincopyprint?

ViewController.m  

ViewController.m [cpp] view plaincopyprint?

- (void)viewDidLoad  

{  

    [super viewDidLoad];  

    webView = [[UIWebView alloc] initWithFrame:CGRectMake(0, 0, 320, 480)];  

    NSURLRequest *request =[NSURLRequest requestWithURL:[NSURL URLWithString:@"http://www.baidu.com"]];  

    [self.view addSubview: webView];  

    [webView loadRequest:request];  

}  

- (void)viewDidLoad {[super viewDidLoad];webView = [[UIWebView alloc] initWithFrame:CGRectMake(0, 0, 320, 480)];NSURLRequest *request =[NSURLRequest requestWithURL:[NSURL URLWithString:@"http://www.baidu.com"]];[self.view addSubview: webView];[webView loadRequest:request]; }运行，这样百度网页就打开了

手机的网络环境是实时变化的，网络慢的时候，怎么提示用户网页正在打开呢？在网页打开出错的时候怎么提示用户呢？这时候我们就需要知道网页什么时候打开的，

什么时候加载完成，什么时候出错了。那么我们需要实现这个<UIWebViewDelegate>协议

3、实现协议，在ViewController.h修改如下：

[cpp] view plaincopyprint?

#import <UIKit/UIKit.h>   

  

@interface ViewController : UIViewController<UIWebViewDelegate>  

{  

    UIWebView *webView;  

}  

@end  

#import <UIKit/UIKit.h>@interface ViewController : UIViewController<UIWebViewDelegate> {UIWebView *webView; } @end
按住control+command+向上键，切换到ViewController.m文件，这是我们在文件中打入- (void) webView，就能看到如下实现方法：

UIWebView中几个重要的函数
1.- (void )webViewDidStartLoad:(UIWebView  *)webView   网页开始加载的时候调用
2.- (void )webViewDidFinishLoad:(UIWebView  *)webView  网页加载完成的时候调用
3.- (void)webView:(UIWebView *)webView  didFailLoadWithError:(NSError *)error 网页加载错误的时候调用

4、实现这三个方法，加入NSLog。

先在viewDidLoad 的webView实例化下面加上

    [webView setDelegate:self];设置代理。这样上面的三个方法才能得到回调。

三个方法实现如下：

[cpp] view plaincopyprint?

<SPAN style="FONT-FAMILY: Arial, Verdana, sans-serif; COLOR: #333333">- (void) webViewDidStartLoad:(UIWebView *)webView  

{  

    NSLog(@"webViewDidStartLoad");  

}  

- (void) webViewDidFinishLoad:(UIWebView *)webView  

{  

    NSLog(@"webViewDidFinishLoad");  

}  

- (void) webView:(UIWebView *)webView didFailLoadWithError:(NSError *)error  

{  

    NSLog(@"didFailLoadWithError:%@", error);  

}  

</SPAN>  

- (void) webViewDidStartLoad:(UIWebView *)webView {NSLog(@"webViewDidStartLoad"); } - (void) webViewDidFinishLoad:(UIWebView *)webView {NSLog(@"webViewDidFinishLoad"); } - (void) webView:(UIWebView *)webView didFailLoadWithError:(NSError *)error {NSLog(@"didFailLoadWithError:%@", error); } 运行打印：

2012-06-23 15:20:29.728 WebViewDemo[1001:f803] webViewDidStartLoad

2012-06-23 15:20:29.991 WebViewDemo[1001:f803] webViewDidFinishLoad

那我们试试error情况，把wifi关掉，运行打印结果：

2012-06-23 15:23:58.939 WebViewDemo[1087:f803] webViewDidStartLoad

2012-06-23 15:23:59.016 WebViewDemo[1087:f803] webViewDidFinishLoad

请求结果不变，为什么关掉网络还成功了呢？缓存？我换163.com试试，这是真正的结果出来了：

2012-06-23 15:24:41.131 WebViewDemo[1134:f803] webViewDidStartLoad

2012-06-23 15:24:41.149 WebViewDemo[1134:f803] didFailLoadWithError:Error Domain=NSURLErrorDomain Code=-1009 "The Internet connection appears to be offline." UserInfo=0x6b41660 {NSErrorFailingURLStringKey=http://www.163.com/, NSErrorFailingURLKey=http://www.163.com/, NSLocalizedDescription=The Internet connection appears to be offline., NSUnderlyingError=0x6eae690 "The Internet connection appears to be offline."}

连接错误了，调用了 didFailLoadWithError。

5、加载等待界面

为了给用户更直观的界面效果，我们加上等待的loading界面试试

在webViewDidStartLoad加入等待

[cpp] view plaincopyprint?

<STRONG>- (void) webViewDidStartLoad:(UIWebView *)webView  

{  

    //创建UIActivityIndicatorView背底半透明View        

    UIView *view = [[UIView alloc] initWithFrame:CGRectMake(0, 0, 320, 480)];    

    [view setTag:108];    

    [view setBackgroundColor:[UIColor blackColor]];    

    [view setAlpha:0.5];    

    [self.view addSubview:view];    

      

    activityIndicator = [[UIActivityIndicatorView alloc] initWithFrame:CGRectMake(0.0f, 0.0f, 32.0f, 32.0f)];    

    [activityIndicator setCenter:view.center];    

    [activityIndicator setActivityIndicatorViewStyle:UIActivityIndicatorViewStyleWhite];    

    [view addSubview:activityIndicator];    

  

    [activityIndicator startAnimating];  

   </STRONG>  

- (void) webViewDidStartLoad:(UIWebView *)webView {//创建UIActivityIndicatorView背底半透明View UIView *view = [[UIView alloc] initWithFrame:CGRectMake(0, 0, 320, 480)]; [view setTag:108]; [view setBackgroundColor:[UIColor blackColor]]; [view setAlpha:0.5]; [self.view addSubview:view]; activityIndicator = [[UIActivityIndicatorView alloc] initWithFrame:CGRectMake(0.0f, 0.0f, 32.0f, 32.0f)]; [activityIndicator setCenter:view.center]; [activityIndicator setActivityIndicatorViewStyle:UIActivityIndicatorViewStyleWhite]; [view addSubview:activityIndicator]; [activityIndicator startAnimating];
加载完成或失败时，去掉loading效果

[cpp] view plaincopyprint?

<STRONG>- (void) webViewDidFinishLoad:(UIWebView *)webView  

{  

    [activityIndicator stopAnimating];  

    UIView *view = (UIView*)[self.view viewWithTag:108];  

    [view removeFromSuperview];  

    NSLog(@"webViewDidFinishLoad");  

  

}  

- (void) webView:(UIWebView *)webView didFailLoadWithError:(NSError *)error  

{  

    [activityIndicator stopAnimating];  

    UIView *view = (UIView*)[self.view viewWithTag:108];  

    [view removeFromSuperview];  

    </STRONG>  

- (void) webViewDidFinishLoad:(UIWebView *)webView {[activityIndicator stopAnimating];UIView *view = (UIView*)[self.view viewWithTag:108];[view removeFromSuperview];NSLog(@"webViewDidFinishLoad");} - (void) webView:(UIWebView *)webView didFailLoadWithError:(NSError *)error {[activityIndicator stopAnimating];UIView *view = (UIView*)[self.view viewWithTag:108];[view removeFromSuperview]; 运行效果：

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