ios - iPad中的UIWebView后退按钮实现问题

Question

我已经通过使用在我的应用程序中实现了一个浏览器UIWebView，默认情况下我在我的浏览器中加载谷歌页面。

当我在 google 页面中搜索某些内容时，会调用UIWebViewDelegate'swebView:shouldStartLoadWithRequest:navigationType:方法。

问题是当我从这个搜索页面点击后退按钮时，没有代表被调用，所以我在禁用我的后退按钮时遇到问题。

此问题仅发生在 iPad 应用程序中，而不发生在 iPhone 应用程序中。

Answer 1

这段代码可以帮助你...

UIWebView 是一个 UIView，它可以加载网页，同时保留在用户的应用程序中。通过使用网页本身中的嵌入链接，可以导航到其他网页。可以使用实例方法 goForward 和 goBack 设置通过历史的向前和向后导航，但程序员必须提供按钮。

以下示例使用 UIWebView，并且

1）添加前进和后退按钮。使用 UIWebViewDelegate 可选方法 webViewDidStartLoad: 和 webViewDidFinishLoad: 启用和突出显示按钮

2) 添加一个 UIActivityIndi​​catorView 在网页加载时显示

在 WebViewController 的 .h 文件中：

声明 UIWebView，可选：添加按钮以控制通过浏览历史和 IBAction 向前和向后移动以按下按钮，可选再次：添加 UIActivityIndi​​catorView。

@interface WebViewController : UIViewController <UIWebViewDelegate>
{
    UIWebView *webView;
    UIButton *back;
    UIButton *forward;
    UIActivityIndicatorView *activityIndicator;
}

@property(nonatomic,retain)IBOutlet UIWebView *webView;
@property(nonatomic,retain)IBOutlet UIButton *back;
@property(nonatomic,retain)IBOutlet UIButton *forward;
@property(nonatomic,retain)IBOutlet UIActivityIndicatorView *activityIndicator;

-(IBAction)backButtonPressed: (id)sender;
-(IBAction)forwardButtonPressed: (id)sender;

@end

//在WebViewController的.m文件中

@implementation WebViewController

@synthesize webView;
@synthesize back;
@synthesize forward;
@synthesize activityIndicator;

//method for going backwards in the webpage history
-(IBAction)backButtonPressed:(id)sender {
    [webView goBack]; 
}

//method for going forward in the webpage history
-(IBAction)forwardButtonPressed:(id)sender
{
    [webView goForward];
}

//programmer defined method to load the webpage

-(void)startWebViewLoad
{
    //NSString *urlAddress = @"http://www.google.com";
    NSString *urlAddress = @"http://cagt.bu.edu/page/IPhone-summer2010-wiki_problemsandsolutions";

    //Create a URL object.
    NSURL *url = [NSURL URLWithString:urlAddress];

    //URL Requst Object
    NSURLRequest *requestObj = [NSURLRequest requestWithURL:url];

    //Load the request in the UIWebView.
    [webView loadRequest:requestObj];
}


// acivityIndicator is set up here
- (void)viewDidLoad
 {
    //start an animator symbol for the webpage loading to follow
    UIActivityIndicatorView *progressWheel = [[UIActivityIndicatorView alloc] initWithActivityIndicatorStyle:UIActivityIndicatorViewStyleGray];

    //makes activity indicator disappear when it is stopped
    progressWheel.hidesWhenStopped = YES;

    //used to locate position of activity indicator
    progressWheel.center = CGPointMake(160, 160);

    self.activityIndicator = progressWheel;
    [self.view addSubview: self.activityIndicator];
    [self.activityIndicator startAnimating];
    [progressWheel release];

    [super viewDidLoad];

    //call another method to do the webpage loading
    [self performSelector:@selector(startWebViewLoad) withObject:nil afterDelay:0];  
}


- (void)dealloc 
{
    [webView release];
    [back release];
    [forward release];
    [activityIndicator release];
    [super dealloc];
}


#pragma mark UIWebViewDelegate methods

//only used here to enable or disable the back and forward buttons
- (void)webViewDidStartLoad:(UIWebView *)thisWebView
{
    back.enabled = NO;
    forward.enabled = NO;
}

- (void)webViewDidFinishLoad:(UIWebView *)thisWebView
{
    //stop the activity indicator when done loading
    [self.activityIndicator stopAnimating]; 

        //canGoBack and canGoForward are properties which indicate if there is 

        //any forward or backward history

    if(thisWebView.canGoBack == YES)
    {
        back.enabled = YES;
        back.highlighted = YES;
    }

    if(thisWebView.canGoForward == YES)
    {
        forward.enabled = YES;
        forward.highlighted = YES;
    }
}

@end

/ * ** * ** * ** * ** * ** * ** * ** * ** * **** /

//In viewDidLoad for the class which adds the WebViewController:


WebViewController *ourWebVC = [[WebViewController alloc] initWithNibName:@"WebViewController" bundle:nil];

ourWebVC.title = @"WebView";
[self.view addSubview:ourWebVC];

//release ourWebVC somewhere else

Answer 2

在您的情况下，您必须忽略/避免“缓存数据”。以下代码行可能会有所帮助。

NSURLRequest *requestObj = [NSURLRequest requestWithURL:[NSURL URLWithString:@"http://www.google.com"] cachePolicy: NSURLRequestReloadIgnoringLocalAndRemoteCacheData timeoutInterval:10.0];
[webView loadRequest:requestObj];