当UIActivityIndicatorView单击IBAction时，IBAction不能工作

Question

我有一个将图像上传到服务器的代码，当图像上传到服务器时，我会放置一个UIActivityIndicatorView。its的UIActivityIndicatorView直到代码结束才会出现，只有在图像上传之后才会出现UIActivityIndicatorView。

这是代码：

- (IBAction)sendTHE:(id)sender {

    _sendTHE.enabled = NO;
    LodingactivityIndicator.hidden = NO;
    [LodingactivityIndicator startAnimating];

    if ([_textmsg.text isEqualToString:@""]) {
        UIAlertView *userExists = [[UIAlertView alloc] initWithTitle:@"Error:" message:@"Please write some message" delegate:self cancelButtonTitle:@"OK" otherButtonTitles:nil];
        [userExists show];
        _sendTHE.enabled = YES;
    }
    else {

        NSString *URLString;
        NSData *storeData = UIImageJPEGRepresentation(_imageView.image, 90);
        if (_imageView.image==NULL)
        {    URLString = [NSString stringWithFormat:@"http://37.142.62.22/the/sendmsg.php?f=ns&t=%@&sn=%@&re=%@", _textmsg.text,_userid,_reciverid];
        }
        else if (_imageView.image!=NULL)
        {    URLString = [NSString stringWithFormat:@"http://37.142.62.22/the/sendmsg.php?f=fs&t=%@&sn=%@&re=%@", _textmsg.text,_userid,_reciverid];
        }
        NSMutableURLRequest *request  = [[NSMutableURLRequest alloc] init];
        [request setURL:[NSURL URLWithString:URLString]];
        [request setHTTPMethod:@"POST"];

        NSString *boundary = @"---------------------------14737809831466499882746641449";
        NSString *contentType = [NSString stringWithFormat:@"multipart/form-data; boundary=%@",boundary];
        [request addValue:contentType forHTTPHeaderField:@"Content-Type"];

        NSMutableData *body = [NSMutableData data];
        [body appendData:[[NSString stringWithFormat:@"\r\n--%@\r\n",boundary] dataUsingEncoding:NSUTF8StringEncoding]];
        [body appendData:[[NSString stringWithFormat:@"Content-Disposition: form-data; name=\"file\"; filename=\"%@.jpg\"\r\n", @"the"] dataUsingEncoding:NSUTF8StringEncoding]];
        [body appendData:[[NSString stringWithFormat:@"Content-Type: application/octet-stream\r\n\r\n"] dataUsingEncoding:NSUTF8StringEncoding]];
        [body appendData:[NSData dataWithData:storeData]];
        [body appendData:[[NSString stringWithFormat:@"\r\n--%@--\r\n", boundary] dataUsingEncoding:NSUTF8StringEncoding]];
        [request setHTTPBody:body];

        NSData *returnData = [NSURLConnection sendSynchronousRequest:request returningResponse:nil error:nil];
        NSString *returnString = [[NSString alloc] initWithData:returnData encoding:NSUTF8StringEncoding];
        [LodingactivityIndicator stopAnimating];


        //NSLog(@"%@",returnString);
        //[self performSegueWithIdentifier:@"showfriends" sender:self];

    }


}

UIActivityIndicatorView在NSURLConnection执行请求后启动。如何在执行请求时显示UIActivityIndicatorView？

Answer 1

您正在主线程上同步执行请求。这意味着在请求返回之前，sendTHE:方法不会返回(并且所有视图都被禁用)。

你有几个选择。

您可以在主线程之外的另一个线程上同步执行请求：

dispatch_async(dispatch_get_global_queue(DISPATCH_QUEUE_PRIORITY_DEFAULT, 0), ^{

    /* Do your networking */ 

    dispatch_async(dispatch_get_main_queue(), ^{

        /* Update your UI with the result */

    });
});

你可以用[NSURLConnection +sendAsynchronousRequest:queue:completionHandler:]。

您可以使用像AFNetworking这样的库来处理这一切。

请记住：

• 不要用耗时的网络和磁盘操作阻止主线程。
• 始终在主线程上更新您的UI