Question

所以我使用NSURLConnection委托在我的AppDelegate.m文件中下载JSON提要。现在我有一个问题。我的应用程序：didFinishLaunchingWithOptions如下所示：

- (BOOL)application:(UIApplication *)application didFinishLaunchingWithOptions:(NSDictionary *)launchOptions {

// Display the progress indicator
HUD = [[MBProgressHUD showHUDAddedTo:self.navigationController.view animated:YES] retain];

// Start the HTTP request
responseData = [[NSMutableData data] retain];
NSURLRequest *request = [NSURLRequest requestWithURL:
                         [NSURL URLWithString:@"*****some url here*********"]];
[[NSURLConnection alloc] initWithRequest:request delegate:self];

// Display the navigation controller
self.window.rootViewController = self.navigationController;
[self.window makeKeyAndVisible];

return YES;

}

所以我所做的就是显示一个活动指示器，启动HTTP请求（这是NSURLConnection委托开始工作的时候），然后我显示我的导航控制器的根视图控制器。现在问题是它将加载具有表视图的视图，其中没有任何数据（因为NSURLConnection）尚未完成下载数据。它看起来很丑陋，因为我在界面构建器上创建了静态UILabel，因此它显示它们然后在加载后它将显示数据。我在屏幕中间有一个活动指示器，因此用户始终知道正在加载新数据。

现在，在我的NSURLConnection完成下载数据之后，由于一些奇怪的原因，视图再次加载了一次。我知道因为如果我把NSLog（@“Test”）;在我的viewDidLoad方法中，它打印出两次。在应用程序结束时：didFinishLaunchingWithOptions并在connectionDidFinishLoading结束时。这是为什么？如何使其看起来整洁，在我的数据加载后视图加载一次？有什么建议吗？

谢谢大家，

编辑：申请前AppDelegate中的更多代码：didFinishLaunchingWithOptions

- (void)hudWasHidden {
    // Remove HUD from screen when the HUD was hidded
    [HUD removeFromSuperview];
    [HUD release];
}

#pragma mark -
#pragma mark NSURLConnectionDelegete

- (void)connection:(NSURLConnection *)connection didReceiveResponse:(NSURLResponse *)response {
    NSLog(@"Starting Response");

    [responseData setLength:0];
    expectedLength = [response expectedContentLength];
    currentLength = 0;

    // Change the progress indicator to the loading wheel
    HUD.mode = MBProgressHUDModeDeterminate;

    NSLog(@"Done Response");
}

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

    NSLog(@"Starting Data");

    [responseData appendData:data];
    currentLength += [data length];

    // Calculate progress indicator progress
    HUD.progress = currentLength / (float)expectedLength;

    NSLog(@"Done Data");
}

- (void)connection:(NSURLConnection *)connection didFailWithError:(NSError *)error {

    NSLog(@"Start Error");

    [HUD hide:YES];

    UIAlertView *alert = [[UIAlertView alloc] 
                          initWithTitle:@"Error" 
                          message:@"Please check your network connection and relaunch the application" 
                          delegate:self 
                          cancelButtonTitle:@"Dismiss" 
                           otherButtonTitles:nil, nil];
    [alert show];
    [alert release];

    [connection release];

    NSLog(@"Done Error");
}

- (void)connectionDidFinishLoading:(NSURLConnection *)connection {

    NSLog(@"Start Finish Loading");

    NSString *responseString = [[NSString alloc] initWithData:responseData encoding:NSUTF8StringEncoding];

    if ([responseString isEqualToString:@"Unable to find specified resource."]) {
        NSLog(@"Unable to find specified resource.n");
    } 

    else {

        ListingsViewController *listingsViewController = [[ListingsViewController alloc] initWithNibName:@"ListingsViewController" bundle:nil];
        listingsViewController.jsonData = responseString;
        [self.navigationController pushViewController:listingsViewController animated:NO];
        [self.navigationController setViewControllers:[NSArray arrayWithObject:listingsViewController] animated:NO];
        [listingsViewController release];
    }

    // Save the pList to the Documents directory in iOS

    ListingsViewController *listingsViewController = (ListingsViewController *)[self.navigationController topViewController];

    NSArray *paths = NSSearchPathForDirectoriesInDomains(NSDocumentDirectory, NSUserDomainMask, YES);
    NSString *documentsDirectoryPath = [paths objectAtIndex:0];
    NSString *plistFilePathInDocumentsDirectory = [documentsDirectoryPath stringByAppendingPathComponent:@"Channels.plist"];

    // Instantiate a modifiable array and initialize it with the content of the plist file
    NSMutableDictionary *channelsData = [[NSMutableDictionary alloc] initWithContentsOfFile:plistFilePathInDocumentsDirectory];

    if (!channelsData) {
        NSString *plistFilePathInMainBundle = [[NSBundle mainBundle] pathForResource:@"Channels" ofType:@"plist"];

        // Instantiate a modifiable array and initialize it with the content of the plist file in main bundle
        channelsData = [[NSMutableDictionary alloc] initWithContentsOfFile:plistFilePathInMainBundle];
    }

    // Set the ListingsViewController's's savedChannels array
    listingsViewController.channelsDict = channelsData;

    [channelsData release];

    // Display progress indicator checkmark and hide
    HUD.customView = [[[UIImageView alloc] initWithImage:[UIImage imageNamed:@"37x-Checkmark.png"]] autorelease];
    HUD.mode = MBProgressHUDModeCustomView;
    [HUD hide:YES afterDelay:1];

    [connection release];
    [responseData release];

    NSLog(@"Done finish loading");
    [window removeFromSuperview];
}

Answer 1

这些都在你的代码中：

    ListingsViewController *listingsViewController = [[ListingsViewController alloc] initWithNibName:@"ListingsViewController" bundle:nil];
    listingsViewController.jsonData = responseString;
    [self.navigationController pushViewController:listingsViewController animated:NO];
    [self.navigationController setViewControllers:[NSArray arrayWithObject:listingsViewController] animated:NO];
    [listingsViewController release];

您正在创建一个新的ListingsViewController并用它替换旧的。新的ListingsViewController尚未加载其视图。（您不需要同时调用-pushViewController:animated:和-setViewControllers:;在这种情况下，第二个会覆盖第一个。）

其他事项：

在-hudWasHidden中，您可能希望[HUD release]; HUD = nil;。
目前尚不清楚[window removeFromSuperview]试图实现什么（它可能什么也没做，因为Windows没有超视图）。

NSURLConnection重新加载我的视图

1 个答案: