iOS 4.3 上传视频时崩溃

Question

我有一个 iPhone 应用程序，它使用 ASIHTTPRequest 将图像和视频上传到 Web 服务。在运行 iOS 5 的设备上一切正常，但在 4.3 及更低版本的设备上从 UIImagePickerController 返回后会崩溃。视频通过选择器进行压缩，然后应用程序崩溃。下面是来自 -(void)imagePickerController: didFinishPickingMediaWithInfo: 方法的代码，也是来自将视频发布到服务器的方法以及从视频中捕获图像以用作缩略图的方法的代码。关于 4.3 中导致崩溃的原因有什么想法吗？

-(void)imagePickerController:(UIImagePickerController *)picker didFinishPickingMediaWithInfo:(NSDictionary *)info
{

self.mediaType = [info objectForKey:UIImagePickerControllerMediaType];

 if ([self.mediaType isEqualToString:(NSString *)kUTTypeMovie])
{
    NSURL *videoURL = [info objectForKey:UIImagePickerControllerMediaURL];

    // Get asset to use for orientation determination   
    AVAsset *myAsset = [AVAsset assetWithURL:videoURL];

    self.videoOrientation = [self UIInterfaceOrientationToString:[self orientationForTrack:myAsset]];

    UIImage *videoThumbnail = [self getVideoThumbnailFromAVAsset:myAsset];
    self.photoImageView.image = videoThumbnail;

    self.videoData = [[NSMutableData alloc]initWithContentsOfURL:videoURL];
}
[self dismissModalViewControllerAnimated:YES]; 
}

-(UIImage*)getVideoThumbnailFromAVAsset:(AVAsset *)myAsset {
AVAssetImageGenerator *imageGenerator = [[AVAssetImageGenerator alloc] initWithAsset:myAsset];

Float64 durationSeconds = CMTimeGetSeconds([myAsset duration]);
CMTime midpoint = CMTimeMakeWithSeconds(durationSeconds/2.0, 600);
NSError *error = nil;
CMTime actualTime;
UIImage *myImage;

CGImageRef halfWayImage = [imageGenerator copyCGImageAtTime:midpoint actualTime:&actualTime error:&error];

if (halfWayImage != NULL) {
    myImage = [UIImage imageWithCGImage:halfWayImage];
    CGImageRelease(halfWayImage);
}
return myImage;
}

- (void)postMessage:(id)sender {

self.uploadButton.enabled = NO;
[self.descriptionTextField resignFirstResponder];
[self.titleTextField resignFirstResponder];

NSUserDefaults *settings = [NSUserDefaults standardUserDefaults];
NSString *sessionKey = [settings stringForKey: @"sessionKey"];

// build URL for request
NSString *baseURL;
NSString *endPoint;

// code here that creates the url component strings baseURL and endPoint

NSString *fullURL = [NSString stringWithFormat:@"%@%@", baseURL, endPoint];
NSURL *url = [NSURL URLWithString:fullURL];

ASIFormDataRequest *request = [ASIFormDataRequest requestWithURL:url];
request.postFormat = ASIMultipartFormDataPostFormat;

NSString *teamIDStr = [NSString stringWithFormat:@"%d",[self.teamID intValue]];

[request setPostValue:sessionKey forKey:@"sessionKey"];
[request setPostValue:teamIDStr forKey:@"TeamID"];   
[request setPostValue:titleTextField.text forKey:@"lessonName"];
[request setPostValue:descriptionTextField.text forKey:@"lessonDesc"];
[request setPostValue:self.videoOrientation forKey:@"videoOrientation"];

//create video file name
NSDate *date1=[NSDate date];
NSDateFormatter *formatter1 = [[NSDateFormatter alloc] init];
[formatter1 setDateFormat:@"hhmm"];
NSString *valuestr = [formatter1 stringFromDate:date1];
NSString *moviename = [NSString stringWithFormat:@"video_%@.mov", valuestr];

[request setData:self.videoData withFileName:moviename andContentType:@"video/quicktime" forKey:@"file1.mov"];

[request setUploadProgressDelegate:self.progressBar];
[request setShowAccurateProgress:YES];
self.progressBar.hidden = NO;
[request setDelegate:self];
[request setTimeOutSeconds:600];
[request startAsynchronous];

}

Answer 1

这个问题的简单答案：AVAsset类方法

+ (id)assetWithURL:(NSURL *)URL

在iOS 5.0之前不可用。您必须使用具体子类 AVURLAsset 来实例化 iOS 4.0 和 4.3 的 AVAsset，并使用其类方法

+ (AVURLAsset *)URLAssetWithURL:(NSURL *)URL options:(NSDictionary *)options