NSCoding Persisting UIImage

问题

I have seen different question on stackoverflow related to this topic. Some says that NSCoding does not conform with UIImage and other says that with iOS 5, it does conform.

I want to persist images in my app. I am using encode and decode methods and everything (title, labels etc) are persisting but NOT the images.

- (void)encodeWithCoder:(NSCoder *)aCoder
{
    [aCoder encodeObject:title forKey:@"title"];
    [aCoder encodeObject:link forKey:@"link"];
    [aCoder encodeObject:creator forKey:@"creator"];
    [aCoder encodeObject:pubDate forKey:@"pubDate"];
  //  [aCoder encodeObject:thumbnail forKey:@"thumbnail"];
    [aCoder encodeObject:UIImagePNGRepresentation(thumbnail) forKey:@"thumbnail"];
}

- (id)initWithCoder:(NSCoder *)aDecoder
{
    self = [super init];
    if (self)
    {
        [self setTitle:[aDecoder decodeObjectForKey:@"title"]];
        [self setLink:[aDecoder decodeObjectForKey:@"link"]];
        [self setCreator:[aDecoder decodeObjectForKey:@"creator"]];
        [self setPubDate:[aDecoder decodeObjectForKey:@"pubDate"]];
        [self setThumbnail:[aDecoder decodeObjectForKey:@"thumbnail"]];        
    }
    return self;
}

I am also using UIPNGRepresentation but its not working. Can someone help me with this.

Thanks.

回答1:

You're not encoding an image. UIImagePNGRepresentation() returns an NSData object. NSData conforms to NSSecureCoding. I haven't worked with that before, but the docs say that you have to decode it like this:

id obj = [decoder decodeObjectOfClass:[MyClass class] forKey:@"myKey"];

After Edit: The above doesn't appear to be necessary. I used the following code in a test app, and both approaches to encoding and decoding an image worked.

- (void)encodeWithCoder:(NSCoder *)aCoder
{
    [aCoder encodeObject:self.name forKey:@"personName"];
    [aCoder encodeObject:self.image2 forKey:@"thumbnail2"];
    [aCoder encodeObject:UIImagePNGRepresentation(self.image1) forKey:@"thumbnail"];
}

- (id)initWithCoder:(NSCoder *)aDecoder
{
    self = [super init];
    if (self)
    {
        [self setName:[aDecoder decodeObjectForKey:@"personName"]];
        [self setImage2:[aDecoder decodeObjectForKey:@"thumbnail2"]];
        [self setImage1:[UIImage imageWithData:[aDecoder decodeObjectForKey:@"thumbnail"]]];
    }
    return self;
}

As Aleph said, the problem must be elsewhere.

回答2:

Try this:


- (void)encodeWithCoder:(NSCoder *)aCoder
{
    [aCoder encodeObject:title forKey:@"title"];
    [aCoder encodeObject:link forKey:@"link"];
    [aCoder encodeObject:creator forKey:@"creator"];
    [aCoder encodeObject:pubDate forKey:@"pubDate"];
    NSData* data = UIImagePNGRepresentation(thumbnail);
    NSLog(@"Data length: %d", data.length);
    [aCoder encodeObject:data forKey:@"thumbnail"];
}

- (id)initWithCoder:(NSCoder *)aDecoder
{
    self = [super init];
    if (self)
    {
        [self setTitle:[aDecoder decodeObjectForKey:@"title"]];
        [self setLink:[aDecoder decodeObjectForKey:@"link"]];
        [self setCreator:[aDecoder decodeObjectForKey:@"creator"]];
        [self setPubDate:[aDecoder decodeObjectForKey:@"pubDate"]];
        NSData* data = [aDecoder decodeObjectForKey:@"thumbnail"];
        NSLog(@"Data length: %d", data.length);
        [self setThumbnail:[UIImage imageWithData:data]];        
    }
    return self;
}

来源：https://stackoverflow.com/questions/14314056/nscoding-persisting-uiimage

标签

iphone

ios

xcode

uiimageview

uiimage