ios - 多点连接减缓 View 创建

Question

我有一个使用 Multipeer Connectivity 的应用程序，当一个设备向组中的其他设备发送数据时，所有其他设备都应该在他们的屏幕上收到数据发送给他们的通知，然后他们可以选择是否发送接受。无论我做什么，我一次又一次遇到的问题是通知 View 至少需要五秒钟才能显示出来，而且大多数时间更长(我什至用我自己的快速和粗略的替代 UIAlertView -如图所示注释掉 - 如果 UIAlertView 是问题，它没有解决任何问题)。我在 session:didReceiveData:fromPeer 中运行了通知代码此 API 的方法。我的 NSLog 在 UIAlertView 上方和下方以及我的粗略替换都快速连续显示， View 显示需要很长时间。有任何想法吗？这是我的代码:

-(void)session:(MCSession *)session didReceiveData:(NSData *)data fromPeer:(MCPeerID *)peerID{
    NSLog(@"DATA RECEIVED: %lu bytes!", (unsigned long)data.length);
    dataReceived = data;
    receivedDataDict = [[NSMutableDictionary alloc] init];
    NSLog(@"Initializing ReceivedDataDict");
    receivedDataDict = [NSKeyedUnarchiver unarchiveObjectWithData:dataReceived];
    NSLog(@"ReceivedDataDict is Unarchived");

    UIAlertView *alert = [[UIAlertView alloc]initWithTitle: @"Hey!"
                                               message: [[NSString alloc] initWithFormat:@"%@ is trying to send you data! Do you accept?", [peerID displayName]]
                                              delegate: self
                                     cancelButtonTitle:@"Nuh Uh!!"
                                     otherButtonTitles:@"Ok, I guess.",nil];
    [alert show];

//    [self.view addSubview:greyOut];
//    
//    CGRect headsUpViewRect = CGRectMake(236, 400, 300, 200);
//    headsUpView = [[UIView alloc] initWithFrame:headsUpViewRect];
//    headsUpView.backgroundColor = [UIColor whiteColor];
//    headsUpView.layer.cornerRadius = 10;
//    
//    CGRect headsUpTitleLblRect = CGRectMake(20, 20, 260, 30);
//    UILabel *headsUpTitleLbl = [[UILabel alloc] initWithFrame:headsUpTitleLblRect];
//    headsUpTitleLbl.text = [[NSString alloc] initWithFormat:@"%@ is trying to send you matches!", [peerID displayName]];
//    headsUpTitleLbl.font = [UIFont systemFontOfSize:15];
//    headsUpTitleLbl.textAlignment = NSTextAlignmentCenter;
//    [headsUpView addSubview:headsUpTitleLbl];
//    
//    CGRect headsUpSubTitleLblRect = CGRectMake(50, 60, 200, 30);
//    UILabel *headsUpSubTitleLbl = [[UILabel alloc] initWithFrame:headsUpSubTitleLblRect];
//    headsUpSubTitleLbl.text = @"Do you accept their gift?";
//    headsUpSubTitleLbl.font = [UIFont systemFontOfSize:10];
//    headsUpSubTitleLbl.textAlignment = NSTextAlignmentCenter;
//    [headsUpView addSubview:headsUpSubTitleLbl];
//    
//    CGRect confirmBtnRect = CGRectMake(200, 120, 80, 50);
//    UIButton *confirmBtn = [UIButton buttonWithType:UIButtonTypeSystem];
//    [confirmBtn addTarget:self action:@selector(headsUpViewClickedButtonAtIndex1) forControlEvents:UIControlEventTouchUpInside];
//    confirmBtn.frame = confirmBtnRect;
//    [confirmBtn setTitle:@"Of Course!" forState:UIControlStateNormal];
//    confirmBtn.backgroundColor = [UIColor colorWithWhite:0.8 alpha:1.0];
//    [headsUpView addSubview:confirmBtn];
//    confirmBtn.layer.cornerRadius = 5;
//    
//    CGRect cancelBtnRect = CGRectMake(20, 120, 80, 50);
//    UIButton *cancelBtn = [UIButton buttonWithType:UIButtonTypeSystem];
//    [cancelBtn addTarget:self action:@selector(cancelHeadsUpView) forControlEvents:UIControlEventTouchUpInside];
//    cancelBtn.frame = cancelBtnRect;
//    [cancelBtn setTitle:@"Nuh Uh!!" forState:UIControlStateNormal];
//    cancelBtn.backgroundColor = [UIColor colorWithWhite:0.8 alpha:1.0];
//    [headsUpView addSubview:cancelBtn];
//    cancelBtn.layer.cornerRadius = 5;
//    
//    headsUpView.transform = CGAffineTransformMakeScale(0.01, 0.01);
//    [self.view addSubview:headsUpView];
//    [UIView animateWithDuration:0.3 delay:0 options:UIViewAnimationOptionCurveEaseOut
//                     animations:^{
//                         headsUpView.transform = CGAffineTransformIdentity;
//                     }
//                     completion:^(BOOL finished){
//                     }];

    NSLog(@"Should Show Alert");
}

NSLog(@"Should Show Alert")在两种编码方法的 View 实际出现之前很久就出现在我的控制台窗口中。数据传输正常工作，所有设备都获得了他们应该获得的数据，但我想知道为什么加载这么小的用户界面需要这么长时间。

Answer 1

原来我的用户界面代码没有作为主线程的一部分被调用，所以我的解决方案看起来像这样:

dispatch_async(dispatch_get_main_queue(), ^(void) {
     UIAlertView *alert = …
});

在 Apple 开发者论坛上向帮助我的人大喊