Why is textView:shouldInteractWithTextAttachment:inRange: never getting called on UITextView delegate? - ios

Question

Is anyone using this delegate method ? I get callbacks on
- (BOOL)textViewShouldBeginEditing:(UITextView *)textView
But not on this one. The documentation seems a bit ambiguous about what this is intended for
- (BOOL)textView:(UITextView *)textView shouldInteractWithTextAttachment:(NSTextAttachment *)textAttachment inRange:(NSRange)characterRange
According to the documentation on the Web this is what its intended for:
Discussion
The text view calls this method if the user taps or long-presses the text attachment and its image property is not nil. Implementation of this method is optional. You can use this method to trigger an action in addition to displaying the text attachment inline with the text.
And here is Xcode 5 documentation:
Asks the delegate if the specified text view should display the provided text attachment in the given range of text.
The text view calls this method when a text attachment character is recognized in its text container by a data detector. Implementation of this method is optional. You can use this method to trigger an alternative action besides displaying the text attachment inline with the text in the given range.
EDIT:
Mmm OK I figured out the problem. If I paste an image in from iOS then it works, however if the image was pasted in from OS X it does not. It seems that the actual attachment formats used are not quite the same on both platforms despite the fact that the image appears to show up correctly in the text views. On closer inspection the NSTextAttachment classes don't appear to be the same on iOS as on OS X.
If anyone can shed any light on the cross platform compatibility here please do.
Also if I save the attributed string after pasting the image in on iOS and then retrieve it and display it in the UITextView interaction with the attachment is no longer possible. It would appear that when storing the image the image is actually placed in contents if contents is nil. So maybe I am going to have to iterate through all attachments to check what data is stored where particularly to figure out any differences in behaviour across the OS X and iOS platforms.
FURTHER EDIT:
The method only gets called if the attachment image is NOT nil and despite the fact that an image is displayed the actual image attribute can actually be nil, silly me! Anyway the fix seems to be to check all the attachments in the attributed string and to set their image attribute to something, usually the contents of the fileWrapper. The default NSTextAttachment behaviour seems to be to store the image in the fileWrapper when its archived but it does not do the reverse when its unarchived. Anyway I want to retain the original image in the attachment but depending on the device display a suitably scaled version of the original !

Answer 1

The chief thing is that the text view's editable property must be NO and it's selectable property must be YES. Those are the only circumstances under which this delegate method is called. If you are getting shouldBeginEditing then your text field is editable which is exactly what it must not be.

Answer 2

Here is what I do to ensure the NSTextAttachments image attribute gets set when restoring the UITextView's attributed string from archived data (in this case whenever the user selects a record from a Core Data store).
I set the UITextView up as a delegate for textStorage and in the didProcessEditing look for any attachments that may have been added and then check that their image attribute is set. I am also setting the scaling factor on the image to make sure the image scales appropriately for the device.
This way I don't loose the original resolution of the image and if the user wants to view it in more detail I provide the option to open it in an image browser window from a popup menu.
Hope this helps someone else.
EDIT:
Check here for more details on NSTextView and UITextView http://ossh.com.au/design-and-technology/software-development/
- (void)textStorage:(NSTextStorage *)textStorage didProcessEditing:(NSTextStorageEditActions)editedMask range:(NSRange)editedRange changeInLength:(NSInteger)delta {
//FLOG(#"textStorage:didProcessEditing:range:changeInLength: called");
[textStorage enumerateAttributesInRange:editedRange options:NSAttributedStringEnumerationLongestEffectiveRangeNotRequired usingBlock:
^(NSDictionary *attributes, NSRange range, BOOL *stop) {
// Iterate over each attribute and look for a Font Size
[attributes enumerateKeysAndObjectsUsingBlock:^(id key, id obj, BOOL *stop) {
if ([[key description] isEqualToString:NSAttachmentAttributeName]) {
NSTextAttachment *attachment = obj;
//Reset the image attribute and scale for the device size if necessary
[self resetAttachmentImage:attachment];
}
}];
}];
}
- (void)resetAttachmentImage:(NSTextAttachment*)attachment {
UIImage *image = [attachment image];
float factor = 2;
if (image == nil) {
if (attachment.fileWrapper == nil || !attachment.fileWrapper.isRegularFile) {
attachment.image = [UIImage imageNamed:#"unknown_attachment.png"];
return;
}
//Usually retrieved from store
image = [UIImage imageWithData:attachment.fileWrapper.regularFileContents];
} else {
// Convert any pasted image
image = [UIImage imageWithData:UIImagePNGRepresentation(image)];
}
float imgWidth = image.size.width;
// If its wider than the view scale it to fit
if (imgWidth > _viewWidth) {
factor = imgWidth / _viewWidth + 0.5;
attachment.image = [UIImage imageWithData:UIImagePNGRepresentation(image) scale:factor];
} else {
attachment.image = [UIImage imageWithData:UIImagePNGRepresentation(image) scale:_scale];
}
}