等待 UIImage

Question

我在 AVCamCaptureManager: 中有这段代码，

- (void) captureStillImage
{
AVCaptureConnection *stillImageConnection = [AVCamUtilities connectionWithMediaType:AVMediaTypeVideo fromConnections:[[self stillImageOutput] connections]];
if ([stillImageConnection isVideoOrientationSupported])
    [stillImageConnection setVideoOrientation:orientation];

[[self stillImageOutput] captureStillImageAsynchronouslyFromConnection:stillImageConnection
                                                     completionHandler:^(CMSampleBufferRef imageDataSampleBuffer, NSError *error) {

                                                         ALAssetsLibraryWriteImageCompletionBlock completionBlock = ^(NSURL *assetURL, NSError *error) {
                                                             if (error) {
                                                                 if ([[self delegate] respondsToSelector:@selector(captureManager:didFailWithError:)]) {
                                                                     [[self delegate] captureManager:self didFailWithError:error];
                                                                     }
                                                             }
                                                         };

                                                         if (imageDataSampleBuffer != NULL) {
                                                             NSData *imageData = [AVCaptureStillImageOutput jpegStillImageNSDataRepresentation:imageDataSampleBuffer];
                                                             //ALAssetsLibrary *library = [[ALAssetsLibrary alloc] init];

                                                             //UIImage *imagePhoto = [[UIImage alloc] initWithData:imageData];
                                                             /*
                                                             [library writeImageToSavedPhotosAlbum:[image CGImage]
                                                                                       orientation:(ALAssetOrientation)[image imageOrientation]
                                                                                   completionBlock:completionBlock];*/
                                                             self.image = [[UIImage alloc] initWithData:imageData]; 

                                                             //[imagePhoto release];

                                                             //[library release];
                                                         }
                                                         else
                                                             completionBlock(nil, error);

                                                         if ([[self delegate] respondsToSelector:@selector(captureManagerStillImageCaptured:)]) {
                                                             [[self delegate] captureManagerStillImageCaptured:self];
                                                         }
                                                     }];
}

而这个方法在另一个类中，

- (IBAction)captureStillImage:(id)sender
{
// Capture a still image
//[[self stillButton] setEnabled:NO];
[[self captureManager] captureStillImage];

if ([captureManager image] == nil) NSLog(@"image nil");

[preview setImage:[captureManager image]];
[snap setAlpha:0.00];
[use setAlpha:1.00];
[retake setAlpha:1.00];

我的问题是，当我调用 IBAction 时，我曾经 image = nil 因为我在 AsynchronouslyFromConnection 中有其他方法；我该怎么办才能解决这种情况？

Answer 1

从您的示例来看，可以将 AVCamCaptureManager 传递给委托。
当它完成捕获图像后，它会在委托上调用 captureManagerStillImageCaptured: 。当委托方法被触发时，您可以完成这项工作，即

-(void)captureManagerStillImageCaptured:(id)sender
{
[preview setImage:[captureManager image]];
[snap setAlpha:0.00];
[use setAlpha:1.00];
[retake setAlpha:1.00];

}

如果您不了解委托的工作原理，那么我建议在这里搜索或提出另一个问题。

委托教程