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Question

我正在尝试确保单例在UI更新之前完成执行。我尝试使用alertView显示请等待并在完成后将其解雇，但它不起作用。然后，当适配器更改状态时，我尝试使用通知中心更新UI中的标签。

点击按钮并等待单身人士完成连接的最佳方式是什么？我应该在dispatch_get_main_queue中移动_adapter和_transporter吗？

 - (IBAction)connectAdapter:(id)sender {
// connnect to adapter
dispatch_queue_t myQueue = dispatch_queue_create("my queue", NULL);
dispatch_async(myQueue, ^{
    [BLEManager sharedInstance];
    NSLog(@"DID RUN BLE MANAGER");
    _adapter = BLEManager.sharedInstance.adapter;
    _transporter = BLEManager.sharedInstance.transporter;
    dispatch_async(dispatch_get_main_queue(), ^{
        //update your UI
        [[NSNotificationCenter defaultCenter] addObserver:self selector:@selector(onAdapterChangedState:) name:AdapterDidUpdateState object:nil];
    });
});
}

更新

如果我在一个带有微调器的警报视图中添加如下代码，我会在异步队列中调用它还是在实例化myQueue之前

UIAlertController *alert = [UIAlertController alertControllerWithTitle:nil
                                                               message:@"Please wait\n\n\n"
                                                        preferredStyle:UIAlertControllerStyleAlert];

UIActivityIndicatorView *spinner = [[UIActivityIndicatorView alloc] initWithActivityIndicatorStyle:UIActivityIndicatorViewStyleWhiteLarge];
spinner.center = CGPointMake(130.5, 65.5);
spinner.color = [UIColor blackColor];
[spinner startAnimating];
[alert.view addSubview:spinner];
[self presentViewController:alert animated:NO completion:nil];

然后我可以使用：

关闭get_main_queue中的警报视图

[alert dismissViewControllerAnimated:YES completion:nil];