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];
该视图作为子视图添加正常.我正在添加的视图包含一个UIWebView,其中包含通常的委托方法,但是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,它崩溃在这条线上..
[self.webView loadHTMLString:stringResponse baseURL:nil];
我已经多次将视图(和UINavigationControllers)显示为subViews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.
.H
@interface MyViewController : UIViewController <UIWebViewDelegate,UIActionSheetDelegate> { //Unrelated IBOutlets } @property (nonatomic,strong) UIWebView *webView; @end
.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
解决方法
该问题与UIWebView无关,而与您的控制器类无关.确实,
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…
解决这个问题的方法是在主控制器类中创建一个新属性或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; }
在释放视图之前将webView委托设置为nil:
- (void)viewDiddisappear:(BOOL)animated { [super viewDiddisappear:animated]; self.webView.delegate = nil; self.webView = nil; }
我还可能会查看您在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.