Question

我创建了一个运行完美的ARC应用程序。它有一个UINavigationController，我用它来浏览视图，一切运行正常。

我正在将应用程序转换为iPad，我决定将其中一个视图显示为popover。（我不喜欢UIPopoverController所以我创建了自己的基本弹出窗口）。它被添加到视图中如下..

MyViewController *hotelinf = [[MyViewController alloc]
initWithNibName:@"MyViewController_iPad" bundle:nil];

[self.view addSubview:hotelinf.view];

该视图被添加为子视图。我正在添加的视图包含一个UIWebView，其中包含常用的委托方法，但当视图尝试访问其中一个委托时，它只会崩溃。

*** -[MyViewController respondsToSelector:]: message sent to deallocated instance 0x7917b90

具体来说，它在这一行崩溃了..

[self.webView loadHTMLString:stringResponse baseURL:nil];

我已经多次将视图（和UINavigationControllers）显示为子视图而没有任何问题，尽管它们都没有包含UIWebView委托。我猜我必须设置我的UIViewController istance的委托，但我不知道如何。值得注意的是，如果我在现有的UINavigationController中推送视图，它会调用并加载HTML，这肯定意味着它与视图本身的代码无关。

任何帮助将不胜感激！这是代码（除了上面显示控制器）..

·H

@interface MyViewController : UIViewController <UIWebViewDelegate, UIActionSheetDelegate> {

//Unrelated IBOutlets

}


@property (nonatomic, strong) UIWebView *webView;

@end

的.m

@implementation MyViewController
@synthesize webView;

- (void)viewDidLoad
{
    [super viewDidLoad];

    self.webView = [[UIWebView alloc]initWithFrame:CGRectMake(317,283,393,354)];
    self.webView.delegate = self;
    [self.view addSubview:self.webView];

    [NSThread detachNewThreadSelector:@selector(getHTMLString) toTarget:self withObject:nil];  
}

-(void)getHTMLString {

    @autoreleasepool {
        //Download a valid HTML String
        [self performSelectorOnMainThread:@selector(loadHTML) withObject:nil waitUntilDone:NO];
    }
}

- (void)viewDidDisappear:(BOOL)animated
{
    [super viewDidDisappear:animated];
    self.webView = nil;
}

-(void)loadHTML {


    self.webView.opaque = NO;
    self.webView.backgroundColor = [UIColor clearColor];
    if ([stringResponse isEqualToString:@""]) {
        UIAlertView *alert = [[UIAlertView alloc] initWithTitle:@"Error" message:@"Could not connect to XXXXX.com. Please verify you are connected to a working 3G/WIFI Network." delegate:self cancelButtonTitle:@"OK" otherButtonTitles:nil];
        [alert show];

    } else {
        //it crashes here only when loaded as a subview - the first access to the delegate
        [self.webView loadHTMLString:stringResponse baseURL:nil];
    }   
}

- (void)connection:(NSURLConnection *)connection didReceiveResponse:(NSURLResponse *)response {
}


- (void)connection:(NSURLConnection *)connection didReceiveData:(NSData *)data {
}

- (void)viewWillAppear:(BOOL)animated
{
    [super viewWillAppear:animated];
}

- (void)webViewDidFinishLoad:(UIWebView *)webView {

        [self stopIndicator];
} 

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

    if (error.code == NSURLErrorCancelled) return; // this is Error -999
    [self stopIndicator];

    // report the error inside the webview
    NSString* errorString = [NSString stringWithFormat:
                             @"<html><center><font size=+10              color='black' face='Helvetica'>An error occurred:<br>%@</font></center></html>",
                             error.localizedDescription];
    [self.webView loadHTMLString:errorString baseURL:nil];

    UIAlertView *alert = [[UIAlertView alloc]
                          initWithTitle:@"Cannot load URL."
                          message:@"You have a connection failure. Please    verify you are connected to a WIFI or 3G enabled Network."
                          delegate:self cancelButtonTitle:@"Ok"     otherButtonTitles:nil];
    [alert show];



}

@end

Answer 1

该问题与UIWebView无关，而与您的控制器类无关。事实上，

MyViewController *hotelinf = [[MyViewController alloc]
   initWithNibName:@"MyViewController_iPad" bundle:nil];

[self.view addSubview:hotelinf.view];

您正在分配控制器并将其分配给局部变量;然后将控制器的视图作为子视图添加到当前视图中。这样做，该视图被保留，但控制器对象本身会发生什么？你发布了吗？或者它泄漏（因为它被分配给局部变量）？

这可能解释了为什么稍后调用respondsToSelector方法时，控制器已被解除分配...

解决此问题的方法是在主控制器类中创建新属性或ivar，并在其中存储MyViewController。不要忘记以dealloc发布它。

我还会建议另一件事。在：

- (void)viewDidDisappear:(BOOL)animated
{
    [super viewDidDisappear:animated];
    self.webView = nil;
}

在发布视图之前将webView委托设置为nil：

- (void)viewDidDisappear:(BOOL)animated
{
    [super viewDidDisappear:animated];
    self.webView.delegate = nil;
    self.webView = nil;
}

我还可以查看您在viewDidDisappear中发布webView的原因。另一方面，您在viewDidLoad中分配它。这种不对称是危险的，因为每当主视图消失（出于任何原因）时，webView将被删除，当视图重新出现时，它就不再存在了。

Answer 2

更好地添加所有委托方法。你没有添加前两个。最有可能的是，当发送消息webViewDidStartLoad时，您的代码会崩溃

– webView:shouldStartLoadWithRequest:navigationType:
– webViewDidStartLoad:
– webViewDidFinishLoad:
– webView:didFailLoadWithError:

令人沮丧的UIWebView委托崩溃问题

2 个答案: