当相机在 iPhone 中运行时使用 UIAlertView

Question

当我的相机使用 OpenCV 检测到人脸时，我尝试触发 AlertView。我设法进行人脸检测并可以成功输出 NSLog。但是，当我尝试触发警报视图时，

NSLog(@"Face Detected");
UIAlertView *alert = [[[UIAlertView alloc] initWithTitle:@"Face Detected" message:@"Do you really  want to try again?" delegate:self cancelButtonTitle:@"Cancel" otherButtonTitles:nil] autorelease];

[alert addButtonWithTitle:@"Yes"];

[alert show];
[alert release];

我可以看到警报视图在屏幕变暗时被触发，但我永远看不到警报视图出来......

感谢您的帮助！

Answer 1

删除[警报发布]。您已经对其调用了 autorelease 。

此外，您还可以将 [alert addButtonWithTitle:@"Yes"]; 集成到初始化程序中：

UIAlertView *alert = [[[UIAlertView alloc] initWithTitle:@"Face Detected" 
                                                message:@"Do you really  want to try again?" 
                                               delegate:self 
                                      cancelButtonTitle:@"Cancel" 
                                      otherButtonTitles:@"OK", nil] autorelease];

Answer 2

你从哪里打电话来的？主线程还是次要线程？
因为 UIKit 的东西应该总是在主线程上完成。

代码示例：

- (void)opencvFaceDetect
{
  // stuff before
  [self performSelectorOnMainThread: @selector(openAlertView) withObject:nil waitUntilDone:false];
  // stuff after
}

然后

- (void)openAlertView
{
  UIAlertView *alert = [[[UIAlertView alloc] initWithTitle:@"Face Detected" 
                                                message:@"Do you really  want to try again?" 
                                               delegate:self 
                                      cancelButtonTitle:@"Cancel" 
                                      otherButtonTitles:@"OK", nil] autorelease];
}