MFMailComposeViewController：附加照片库中的图像

Question

I am having a bit of trouble attaching images from the Photo Gallery to an email.

Basically, one of the features of my application allow the user to take photos. When they snap the shot, I record the URL Reference to the image in Core Data. I understand that you have to go through the ALAssetRepresentation to get to the image. I have this up and running within my application for when the user wants to review an image that they have taken.

I am now attempting to allow the user to attach all of the photos taken for an event to an email. While doing this, I iterate through the Core Data entity that stores the URL References, call a method that returns a UIImage from the ALAssetsLibrary and then attaches it using the NSData / UIImageJPEGRepresentation and MFMailComposeViewController / addAttachmentData methods.

Problem is: When the email is presented to the user, there are small blue squares representing the images and the image is not attached.

Here is the code:

- (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];

    }

}

and the method that returns the 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;

}

NOTE: This above code does run, it simply does not attach the image. Also, note, I am able to successfully attach images from the gallery within my application, as long at I have set them into a UIImageView .Image already (basically, I am taking the pointer to the image from the UIImageView and passing it to the addAttachmentData method.) It is just when I attempt to iterate through Core Data and attach without first setting the image into a UIImageView that I have the trouble.

Any tips would be greatly appreciated!

Thanks! Jason

Answer 1

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
    [...]
}