消息发送到iPhone中的已释放实例

Question

我是新来的iPhone，

我正在按照苹果在这里的建议创建NSURLConnection，但是当我关闭视图时我的应用程序崩溃了，我尝试了NSZombieEnabled概念，该概念向我显示-[CALayer release]: message sent to deallocated instance 0x68b8f40

我正在Webview显示一个网页，当用户单击Webview下载链接时，我将在创建NSURLConnection此方法中调用shouldStartLoadWithRequest方法。

这是我的代码段，

- (void)connection:(NSURLConnection *)connection didReceiveResponse:(NSURLResponse *)response
{
    [receivedData setLength:0];
}

- (void)connection:(NSURLConnection *)connection didReceiveData:(NSData *)data1
{
    [receivedData appendData:data1];
}

- (void)connectionDidFinishLoading:(NSURLConnection *)connection
{
    NSLog(@"Succeeded! Received %d bytes of data",[receivedData length]);

    DirPath=[self applicationDocumentsDirectory];

     NSLog(@"DirPath=%@",DirPath);
    [receivedData writeToFile:DirPath atomically:YES];

    UIAlertView* Alert = [[UIAlertView alloc] initWithTitle:@"Download Complete !"
                                                         message:nil delegate:nil 
                                               cancelButtonTitle:@"OK"
                                               otherButtonTitles:nil];
    [Alert show];
    [Alert release];


    // release the connection, and the data object
    [connection release];
    [receivedData release];
}


- (void)connection:(NSURLConnection *)connection didFailWithError:(NSError *)error1
{
    [connection release];
    [receivedData release];

    // inform the user
    NSLog(@"Connection failed! Error - %@ %@",
          [error1 localizedDescription],
          [[error1 userInfo] objectForKey:NSURLErrorFailingURLStringErrorKey]);
}

- (BOOL)webView:(UIWebView*)webView shouldStartLoadWithRequest:(NSURLRequest*)request navigationType:(UIWebViewNavigationType)navigationType {


    //CAPTURE USER LINK-CLICK.

            Durl=[[url absoluteString]copy];

            //Checking for Duplicate .FILE at downloaded path....

            BOOL success =[[NSFileManager defaultManager] fileExistsAtPath:path];
            lastPath=[[url lastPathComponent] copy];

            if (success) //if duplicate file found...
            {
                UIAlertView* Alert = [[UIAlertView alloc] initWithTitle:@"This FILE is already present in Library."
                                                                     message:@"Do you want to Downlaod again ?" delegate:self 
                                                           cancelButtonTitle:nil
                                                           otherButtonTitles:@"Yes",@"No",nil];
                [Alert show];
                [Alert release];

            }
            else  //if duplicate file not found directly start download...
            {
                // Create the request.
                NSURLRequest *theRequest=[NSURLRequest requestWithURL:[NSURL URLWithString:Durl]
                                                          cachePolicy:NSURLRequestUseProtocolCachePolicy
                                                      timeoutInterval:60.0];

                // create the connection with the request and start loading the data
                NSURLConnection *theConnection=[[NSURLConnection alloc] initWithRequest:theRequest delegate:self];
                if (theConnection) {
                    // Create the NSMutableData to hold the received data.
                    receivedData = [[NSMutableData data] retain];
                } else {
                    NSLog(@"Inform the user that the connection failed."); 
                }

    return YES;   
}

任何帮助将不胜感激。

Answer 1

确保在实现dealloc时将delegate重置为nil 。 这样做的另一个地方是viewWillDisappear:

您的应用崩溃/访问僵尸的原因是，即使UIWebView实例已经被释放，它也可能会尝试回调viewController。 为了防止这种情况，您必须在viewController超出范围之前将该UIWebView的delegate设置回nil 。 在iOS5的ARC实施之前使用委托时，这是一个普遍的问题。 iOS5的最后提供弱引用，实际上那些nil自己一旦他们的实例得到释放。

范例A：

- (void)dealloc
{
    [...]
    _webView.delegate = nil;
}

范例B：

- (void)viewWillDisappaer:(BOOL)animated
{
    [super viewWillDisappaer:animated];
    _webView.delegate = nil;
}

---

编辑：再次阅读您的问题后，我意识到僵尸是UIView还是UIControl，因为消息已发送到CALayer。 通过暂时删除所有与webView相关的代码，确保您的问题实际上与web视图有关。

Answer 2

我认为此NSURLConnection *theConnection=[[NSURLConnection alloc] initWithRequest:theRequest delegate:self];问题NSURLConnection *theConnection=[[NSURLConnection alloc] initWithRequest:theRequest delegate:self];

您正在创建的实例NSURLConnection有代表自我，当您关闭视图一切都得到了deallocated的这一观点。 但是，当NSURLConnection尝试调用它的委托方法时，将会发生崩溃。

因此，您需要在viewWillDisappear中将NSURLConnection的委托设置为nil，以实现此目的，您需要在接口中创建NSURLConnection对象。

@interface yourClass
{
   NSURLConnection *theConnection;
}
@end

在.m中

theConnection=[[NSURLConnection alloc] initWithRequest:theRequest delegate:self];

- (void)viewWillDisappaer:(BOOL)animated
{
    [super viewWillDisappaer:animated];
    theConnection.delegate = nil;
}