Question

我需要显示活动指标，但无法找到正确的方法，我尝试的是：

In ViewDidLoad

[self-performSelectOnMainThread:@selector（setupActivityIndicator）withObject:nil waitUntilDone:NO]


[self-userDataFromServer]；
[self-performSelectionOnMainThread:@selector（stopActivityIndicatorInMainThread）withObject:nil waitUntilDone:NO]
----或者-----

In ViewDidLoad

[self-startActivityIndicator]

[self-userDataFromServer]；
[self-stopActivityIndicator]

两人都在以这种不正确的方式工作。我们如何在并行线程上使用activityindicator？

Answer 1

根据我的经验，从服务器下载数据的最佳实践是

- (void)viewDidLoad {
   [self startActivityIndicator];
    NSURLConnection *conn = [[NSURLConnection alloc] initWithRequest:
                             [NSURLRequest requestWithURL:
                              [NSURL URLWithString:aRequest]] delegate:self];
    [conn release];
}

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

- (void)connection:(NSURLConnection *)connection didFailWithError:(NSError *)error {
    NSLog(@"ERROR DOWNLOADING");

    // Here you can display an UIAlert message

    // Then stop your activity indicator
    [self stopActivityIndicator];

    // Release the connection now that it s finished
    connection = nil;

}

- (void)connectionDidFinishLoading:(NSURLConnection *)connection {
    NSLog(@"FINISH DOWNLOAD");

    // Or just stop
    [self stopActivityIndicator];

    // Do something

    // Release the connection now that it s finished
    connection = nil;
}

Answer 2

没有必要在viewDidLoad中调用performSelectorOnMainThread:，因为您很可能已经在主线程上了。UIKit是UIActivityIndicator的一部分，无论如何都需要从主线程调用它。

我认为您可能想要做的是在辅助线程上运行userDataFromServer。在视图中DidLoad尝试

[self performSelectorInBackground:@selector(userDataFromServer) withObject:nil];

然后，在您的userDataFromServer方法中，确保包含一个NSAutoreleasePool

-(void)userDataFromServer {
        NSAutoreleasePool *pool = [[NSAutoreleasePool alloc] init];
        //code to actually get the data
       [pool release];
}

Answer 3

活动指示器只是显示有活动。

例如，如果您正在使用NSURLConnection在单独的线程上运行NSURLRequest，您将在viewDidLoad上向视图中添加活动指示符，然后在执行[urlConnection start]时执行[activityIndicator startAnimationing]

我假设你的问题是，你正在做的事情是将iphone“挂”在userDataFromServer中，所以最好在另一个线程上执行该选择器。你能把那个方法贴出来吗？如果您使用的是NSURLRequest，那么如果您添加[NSURLConnectionWithRequest:myRequest]并查找NSURLConnection委托方法，那么这对您来说是异步的。

友情链接