ios - 如何从 Amazon S3 下载 - iOS

Question

我正在尝试从我的 Amazon S3 存储桶 (v2) 下载图像，但无法弄清楚。我不断从 [transferManager download:downloadRequest] 获取 null；

已填写所有帐户详细信息/ key 。感谢任何帮助。

-(void) startApp:(NSDictionary *)launchOptions {
// create credentials
AWSCognitoCredentialsProvider *credentialsProvider = [AWSCognitoCredentialsProvider credentialsWithRegionType:AWSRegionUSEast1
                                                                                                accountId:@"xxxx-xxxx-xxxx"
                                                                                               identityPoolId: @"us-east-1:xxxxxxx-xxxx-xxxx-xxxx-xxxxxxxxxxx"
                                                                                                unauthRoleArn:@"Cognito_AppUnauth_DefaultRole"
                                                                                                  authRoleArn:nil];
AWSServiceConfiguration *configuration = [AWSServiceConfiguration configurationWithRegion:AWSRegionUSEast1
                                                                      credentialsProvider:credentialsProvider];
[AWSServiceManager defaultServiceManager].defaultServiceConfiguration = configuration;
}

- (instancetype) init {
AWSS3TransferManagerDownloadRequest *downloadRequest = [AWSS3TransferManagerDownloadRequest new];
downloadRequest.bucket = @"mybucket.s3.amazonaws.com";
downloadRequest.key = @"XXXXXXXXXXXXXXX";
downloadRequest.downloadingFileURL = [NSURL URLWithString:@"https://s3.amazonaws.com/MYBUCKET/hello.png"];
[self download:downloadRequest];

return self;
}
- (BFTask *)download:(AWSS3TransferManagerDownloadRequest *)downloadRequest {
NSLog(@"Download request: %@", downloadRequest);
AWSS3TransferManager *transferManager = [AWSS3TransferManager defaultS3TransferManager];
NSLog(@"%@", [transferManager download:downloadRequest]);
return nil;
}

Answer 1

首先，您滥用了 AWSS3TransferManagerDownloadRequest 的 downloadingFileURL 属性。 downloadingFileURL 不应引用您从中获取的 S3 位置；相反，它应该指的是您正在写入该文件的磁盘位置到，例如:

NSString *downloadingFilePath = [NSTemporaryDirectory()stringByAppendingPathComponent:@"hello.png"];
NSURL *downloadingFileURL = [NSURL fileURLWithPath:downloadingFilePath];

一旦该文件下载完成，它将出现在该文件路径中。

不过，要知道您的文件何时准备就绪，我建议像这样在一个 block 中执行您的下载请求:

[[transferManager download:downloadRequest]continueWithExecutor
    [BFExecutor mainThreadExecutor] withBlock:^id(BFTask *task) {
    if (task.result) {
        AWSS3TransferManagerDownloadOutput *downloadOutput = task.result;
        self.fetchedImage = [UIImage imageWithContentsOfFile:downloadingFilePath];
    } else if (task.error) {
        NSLog(@"Error: %@", task.error);
    }
}];