1

我在将照片库中的图像附加到电子邮件时遇到了一些问题。

基本上，我的应用程序的一项功能允许用户拍照。当他们拍摄照片时，我会在 Core Data 中记录对图像的 URL 引用。我知道您必须通过ALAssetRepresentation才能获得图像。当用户想要查看他们拍摄的图像时，我在我的应用程序中启动并运行了它。

我现在正试图允许用户将所有为事件拍摄的照片附加到电子邮件中。在执行此操作时，我遍历存储 URL 引用的 Core Data 实体，调用从 中返回 a 的方法，UIImage然后ALAssetsLibrary使用NSData/UIImageJPEGRepresentation和MFMailComposeViewController/addAttachmentData方法附加它。

问题是：当电子邮件呈现给用户时，有代表图像的蓝色小方块，并且没有附加图像。

这是代码：

- (void)sendReportReport
{

    if ([MFMailComposeViewController canSendMail])
    {

        MFMailComposeViewController *mailer = [[MFMailComposeViewController alloc] init];

        mailer.mailComposeDelegate = self;

        [mailer setSubject:@"Log: Report"];

        NSArray *toRecipients = [NSArray arrayWithObjects:@"someone@someco.com", nil];
        [mailer setToRecipients:toRecipients];


        NSError *error;

        NSFetchRequest *fetchPhotos = [[NSFetchRequest alloc] init];
        NSEntityDescription *entity = [NSEntityDescription 
                                       entityForName:@"Photo" inManagedObjectContext:__managedObjectContext];
        [fetchPhotos setEntity:entity];
        NSArray *fetchedPhotos = [__managedObjectContext executeFetchRequest:fetchPhotos error:&error];
        int counter;

        for (NSManagedObject *managedObject in fetchedPhotos ) {
            Photo *photo = (Photo *)managedObject;

//            UIImage *myImage = [UIImage imageNamed:[NSString stringWithFormat:@"%@.png", counter++]];
            NSData *imageData = UIImageJPEGRepresentation([self getImage:photo.referenceURL], 0.5);
//            NSData *imageData = UIImagePNGRepresentation([self getImage:photo.referenceURL]);
//            [mailer addAttachmentData:imageData mimeType:@"image/jpeg" fileName:[NSString stringWithFormat:@"%i", counter]];  
            [mailer addAttachmentData:imageData mimeType:@"image/jpeg" fileName:[NSString stringWithFormat:@"a.jpg"]];  

            counter++;

        }


        NSString *emailBody = [self getEmailBody];

        [mailer setMessageBody:emailBody isHTML:NO];

        [self presentModalViewController:mailer animated:YES];

    }
    else
    {
        UIAlertView *alert = [[UIAlertView alloc] initWithTitle:@"Failure"
                                                        message:@"Your device doesn't support the composer sheet"
                                                       delegate:nil
                                              cancelButtonTitle:@"OK"
                                              otherButtonTitles:nil];
        [alert show];

    }

}

以及返回的方法UIImage：

#pragma mark - Get Photo from Asset Library
+ (ALAssetsLibrary *)defaultAssetsLibrary {
    static dispatch_once_t pred = 0;
    static ALAssetsLibrary *library = nil;
    dispatch_once(&pred, ^{
        library = [[ALAssetsLibrary alloc] init];
    });
    return library; 
}

- (UIImage *)getImage:(NSString *)URLReference
{

    __block UIImage *xPhoto = nil;

    ALAssetsLibraryAssetForURLResultBlock resultblock = ^(ALAsset *myasset)
    {
        UIImage *xImage;

        // get the image
        ALAssetRepresentation *rep = [myasset defaultRepresentation];
        CGImageRef iref = [rep fullScreenImage];

        if (iref) {
            xImage = [UIImage imageWithCGImage:iref];
        }

        xPhoto = xImage;

    };


    ALAssetsLibraryAccessFailureBlock failureblock  = ^(NSError *myerror)
    {
        NSLog(@"Error fetching photo: %@",[myerror localizedDescription]);
    };


    NSURL *asseturl = [NSURL URLWithString:URLReference];

    // create library and set callbacks
    ALAssetsLibrary *al = [DetailsViewController defaultAssetsLibrary];
    [al assetForURL:asseturl 
        resultBlock:resultblock
       failureBlock:failureblock];   

    return xPhoto;

}

注意：上面的代码确实运行，它只是不附加图像。另外，请注意，只要我已经将它们设置为UIImageView.Image ，我就可以在我的应用程序中成功地附加图像（基本上，我正在从图像中获取指向图像的指针UIImageView并将其传递给addAttachmentData方法。 ) 只是当我尝试遍历 Core Data 并在没有先将图像设置为 a 的情况下进行附加时UIImageView，我遇到了麻烦。

任何提示将非常感谢！

谢谢！杰森

4

1 回答 1

5

Oh now I see it.. sry. You are using an asynchronous block to get the image from the asset library. But right after starting that operation, you are returning xImage. But the asynchronous operation will finish later. So you are returning nil.

You need to change your architectur to smth like this:

In your .h file you need two new members:

NSMutableArray* mArrayForImages;
NSInteger mUnfinishedRequests;

In your .m file do smth like that:

- (void)sendReportReport
{
    // save image count
    mUnfinishedRequests = [fetchedPhotos count];

    // get fetchedPhotos
    [...]

    // first step: load images
    for (NSManagedObject *managedObject in fetchedPhotos )
    {
        [self loadImage:photo.referenceURL];    
    }
}

Change your getImage method to loadImage:

- (void)loadImage:(NSString *)URLReference
{
    NSURL *asseturl = [NSURL URLWithString:URLReference];

    ALAssetsLibraryAssetForURLResultBlock resultblock = ^(ALAsset *myasset)
    {    
        // get the image
        ALAssetRepresentation *rep = [myasset defaultRepresentation];
        CGImageRef iref = [rep fullScreenImage];

        if (iref) {
            [mArrayForImages addObject: [UIImage imageWithCGImage:iref]];
        } else {
            // handle error
        }

        [self performSelectorOnMainThread: @selector(imageRequestFinished)];
    };

    ALAssetsLibraryAccessFailureBlock failureblock  = ^(NSError *myerror)
    {
        NSLog(@"Error fetching photo: %@",[myerror localizedDescription]);

        [self performSelectorOnMainThread: @selector(imageRequestFinished)];
    };


    // create library and set callbacks
    ALAssetsLibrary *al = [DetailsViewController defaultAssetsLibrary];
    [al assetForURL:asseturl 
        resultBlock:resultblock
       failureBlock:failureblock];
}

Create a new callback method:

- (void) imageRequestFinished
{
    mUnfinishedRequests--;
    if(mUnfinishedRequests <= 0)
    {
       [self sendMail];
    }
}

And an extra method for finally sending the mail, after getting the images:

- (void) sendMail
{
    // crate mailcomposer etc
    [...]

    // attach images
    for (UIImage *photo in mArrayForImages )
    {
                NSData *imageData = UIImageJPEGRepresentation(photo, 0.5);
                [mailer addAttachmentData:imageData mimeType:@"image/jpeg" fileName:[NSString stringWithFormat:@"a.jpg"]];
    }

    // send mail
    [...]
}
于 2012-03-07T09:49:42.150 回答