iOS 7 UITextView: Size of nstextattachment getting 2x after reopening the application

问题

I am building a note editor using the Text Kit in ios7. Earlier I had trouble in rendering of custom size NSTextAttachment's as it was slowing down the rendering to a great extent.I solved the issue by scaling the images and then adding them to textview.You can find my answer in iOS 7.0 UITextView gettings terribly slow after adding images to it After scaling the images the textview rendering runs fine without any lag.The attributed text of textview is stored in core data.During a running session of application the textview displays the images correctly.Even after saving the attributed text in the core data and retrieving it again to display on textview,the images look fine.But after killing the app and again running the application.The images get enlarged to 2x size.while scaling the images I used the following function and used [[UIScreen bounds] scale] to maintain the image quality.

- (UIImage *)imageWithImage:(UIImage *)image scaledToSize:(CGSize)newSize {

     UIGraphicsBeginImageContextWithOptions(newSize, NO, [UIScreen mainScreen].scale);
    [image drawInRect:CGRectMake(0, 0, newSize.width, newSize.height)];
    UIImage *newImage = UIGraphicsGetImageFromCurrentImageContext();
    UIGraphicsEndImageContext();
    return newImage;
}

If I scale the images to 1.0 the images doesn't expand but the image quality is very bad.

What I Think where the problem lies? The problem lies in the layout manager.

What I have Tried I have tried subclassing the NSLayoutManager and overriding the - (void)drawGlyphsForGlyphRange:(NSRange)glyphsToShow atPoint:(CGPoint)origin What I see is the attachment size is doubling when running a new session of the application.If I try to check the size of attachment and resize it.The lag starts coming again. I am stucked with this problem from a quite time.Any suggestions would be much appreciated.

回答1:

Could the reason due to retina display? If it is retina, you might need to reduce the size by 50% before storing. How about trying this:-

 //Original Size that you want to store
CGSize imageSize = CGSizeMake(320.0f, 320.0f);

//Make the image 50% of the size for retina
if ([[UIScreen mainScreen] respondsToSelector:@selector(displayLinkWithTarget:selector:)] &&([UIScreen mainScreen].scale == 2.0)) {
    // Retina display
    imageSize = CGSizeMake(160.0f, 160.0f);
}

UIImage * storeImage = [self imageWithImage:self.image scaledToSize:imageSize]
//TODO: Store this image locally or whatever you want to do.

回答2:

@interface MMTextAttachment : NSTextAttachment
{
}
@end
@implementation MMTextAttachment
//I want my emoticon has the same size with line's height
- (CGRect)attachmentBoundsForTextContainer:(NSTextContainer *)textContainer proposedLineFragment:(CGRect)lineFrag glyphPosition:(CGPoint)position characterIndex:(NSUInteger)charIndex NS_AVAILABLE_IOS(7_0)
{
return CGRectMake( 0 , 0 , lineFrag.size.height , lineFrag.size.height );
}
@end

I think you can try this.

来源：https://stackoverflow.com/questions/23300349/ios-7-uitextview-size-of-nstextattachment-getting-2x-after-reopening-the-applic

标签

ios7

uitextview

textkit

nslayoutmanager

nstextattachment