在目標C中下載圖像表格AWS S3

Question

因此，我嘗試從Amazon AWS S3下載圖片，並使用它們提供的模板代碼，但無法正常工作。

NSString *downloadFilePath = [NSTemporaryDirectory() stringByAppendingString:@"download-testImage.jpg"];
NSURL *downloadFileURL = [NSURL fileURLWithPath:downloadFilePath];
AWSS3TransferManagerDownloadRequest *downloadRequest = [AWSS3TransferManagerDownloadRequest new];

downloadRequest.bucket = @"tempBucketName"; //changed name for security reasons
downloadRequest.key = @"testImage.jpg";
downloadRequest.downloadingFileURL = downloadFileURL;
NSLog(@"About to start");
// Download the file.
[[self.transferManager download:downloadRequest] continueWithExecutor:[AWSExecutor mainThreadExecutor] withBlock:^id(AWSTask *task) {
    NSLog(@"Started task");
   if (task.error){
       NSLog(@"In if statement");
       if ([task.error.domain isEqualToString:AWSS3TransferManagerErrorDomain]) {
           switch (task.error.code) {
               case AWSS3TransferManagerErrorCancelled:
               case AWSS3TransferManagerErrorPaused:
                   break;

               default:
                   NSLog(@"Error: %@", task.error);
                   break;
           }
       } else {
           // Unknown error.
           NSLog(@"Error: %@", task.error);
       }
   }
   if (task.result) {
       AWSS3TransferManagerDownloadOutput *downloadOutput = task.result;
       //File downloaded successfully.
       NSLog(@"success");
   }
   return nil;
}];
cell.postImage.image = [UIImage imageWithContentsOfFile:downloadFilePath];
NSLog(@"%f", [UIImage imageWithContentsOfFile:downloadFilePath].size.width);

唯一要打印的是“即將開始”“完成”，最后打印的圖像大小為0.0。 我添加了這些NSLogs以幫助你們查明我的問題，我該如何解決？

Answer 1

下載是異步的，因此您需要將其分派到主隊列，即

if (task.result) {
   AWSS3TransferManagerDownloadOutput *downloadOutput = task.result;
   //File downloaded successfully.

 NSLog(@"success");

   dispatch_async(dispatch_get_main_queue(), ^{
            cell.postImage.image = [UIImageimageWithContentsOfFile:downloadFilePath];
NSLog(@"%f", [UIImage imageWithContentsOfFile:downloadFilePath].size.width);
        });

}