UIWebview向前然后向后并不总是有效

Question

我使用以下代码进行Webview导航。

下面的代码适用于一些URL，但它不起作用的一些URL ..我不知道我的错误在我的代码...

。H

#import <UIKit/UIKit.h>

@interface WebviewViewController : UIViewController <UIWebViewDelegate>
{
    IBOutlet UIWebView * webview;
    IBOutlet UIToolbar * tBar;
    IBOutlet UIBarButtonItem * backbtn;
    IBOutlet UIBarButtonItem * forwardbtn;
}
@property (nonatomic, retain) IBOutlet UIWebView * webview;
@property (nonatomic, retain) IBOutlet UIBarButtonItem * backbtn;
@property (nonatomic, retain) IBOutlet UIBarButtonItem * forwardbtn;
@property (nonatomic, retain) UIToolbar * tBar;
- (IBAction)goBackbttn:(id)sender;
- (IBAction)goForwardbttn:(id)sender;
@end

.M

#import "WebviewViewController.h"
@implementation WebviewViewController
@synthesize webview;
@synthesize tBar, backbtn, forwardbtn;
- (void)viewDidLoad {
    [super viewDidLoad];
    [backbtn setEnabled : FALSE];
    [forwardbtn setEnabled : FALSE];
    NSString * urlAddress = @ "http://www.exampl.com";
    NSURL * url = [NSURL URLWithString:urlAddress];
    NSURLRequest * requestObj = [NSURLRequest requestWithURL:url];
    webview.scalesPageToFit = YES;
    webview.autoresizesSubviews = YES;
    [webview loadRequest : requestObj];
}

- (IBAction)goBackbttn:(id)sender
{
    [forwardbtn setEnabled : TRUE];
}

- (IBAction)goForwardbttn:(id)sender {
    [webview goForward];
}

- (void)webViewDidFinishLoad:(UIWebView *)webView
{
    [backbtn setEnabled :[webView canGoBack]];
    [forwardbtn setEnabled :[webView canGoForward]];
}

- (void)didReceiveMemoryWarning {
    [super didReceiveMemoryWarning];
}

- (void)viewDidUnload {
}

- (void)dealloc {
    [super dealloc];
}
@end

Answer 1

这不应该吗

- (IBAction)goBackbttn:(id)sender
{
    [forwardbtn setEnabled : TRUE];
}

是这样的：

- (IBAction)goBackbttn:(id)sender
{
    [webview goBack];
}

？