State Preservation and Restoration UIImageView added from button event

Question

I am adding UIImageView on a button click. I want to restore it using UIKit. I am getting restoration identifier in:

 - (void)decodeRestorableStateWithCoder:(NSCoder *)coder;

How can I decode this UIImageView?

you should encode & decode the image not imageview. in staterestoration process. — Pawan Rai, Feb 18 '14 at 19:53
imageview in either not in my .h file nor in xib file. i am making and adding that imageview to view on button click.i need to reconstruct the imageview? — Jawad Ali, Feb 18 '14 at 20:04
there is a solution for it to. you have to make a collection of images. encode & decode this collection. you should try this by your self. — Pawan Rai, Feb 18 '14 at 20:11
you need a custom class , which will have two properties. 1st will hold the image 2nd will hold the position. make you custom object add them to mutable array & encode it . again while decoding you will get the collection of image that will hold the image & there position. try it — Pawan Rai, Feb 18 '14 at 20:21
how can i save image transform ? in my app user can zoom pan scale the image — Jawad Ali, Feb 19 '14 at 03:27
last question .. is that what pic collage is doing ? any guess — Jawad Ali, Feb 19 '14 at 12:12

Rafał Sroka · Answer 1 · 2014-02-18T20:03:21.443

1

To make the state preservation and restoration work there are two steps that are always required:

The App delegate must opt-in
Each view controller or view to be preserved/restored must have a restoration identifier assigned.

You should also implement encodeRestorableStateWithCoder: and decodeRestorableStateWithCoder: for views and view controllers that require state to be saved and restored.

Add the following methods to the view controller of your UIImageView.

-(void)encodeRestorableStateWithCoder:(NSCoder *)coder
{
    [coder encodeObject:UIImagePNGRepresentation(_imageView.image)
                 forKey:@"YourImageKey"];

    [super decodeRestorableStateWithCoder:coder];
}

-(void)decodeRestorableStateWithCoder:(NSCoder *)coder
{
    _imageView.image = [UIImage imageWithData:[coder decodeObjectForKey:@"YourImageKey"]];

    [super encodeRestorableStateWithCoder:coder];
}

State preservation and restoration is an optional feature so you need to have the application delegate opt-in by implementing two methods:

- (BOOL)application:(UIApplication *)application shouldSaveApplicationState:(NSCoder *)coder
{
    return YES;
}

- (BOOL)application:(UIApplication *)application shouldRestoreApplicationState:(NSCoder *)coder
{
    return YES;
}

Useful article about state preservation: http://useyourloaf.com/blog/2013/05/21/state-preservation-and-restoration.html

edited Feb 18 '14 at 20:03

answered Feb 18 '14 at 19:55

Rafał Sroka

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i am adding imageview from code its not initialized in my header file – Jawad Ali Feb 18 '14 at 19:57
do you think , without converting uiimage into nsdata , you can encode & decode it. – Pawan Rai Feb 18 '14 at 19:57
on button click i use to do this – Jawad Ali Feb 18 '14 at 19:58
just declare the imageview in .h file so you can get a reference for imageview & get the current image. – Pawan Rai Feb 18 '14 at 19:59
uiimageview * myimage =[uiimageview alloc ]init]; – Jawad Ali Feb 18 '14 at 19:59
in my app user can add as many images as he want to. so how can i declare them all in .h file ? – Jawad Ali Feb 18 '14 at 20:00

score 1 · Accepted Answer · answered Feb 18 '14 at 19:56

i have used this code in one of my app.

here is the encoding & decoding process

-(void)encodeRestorableStateWithCoder:(NSCoder *)coder
{

NSData *imageData=UIImagePNGRepresentation(self.imgViewProfilePicture.image);
[coder encodeObject:imageData forKey:@"PROFILE_PICTURE"];
[super encodeRestorableStateWithCoder:coder];
}

-(void)decodeRestorableStateWithCoder:(NSCoder *)coder
{

self.imgViewProfilePicture.image=[UIImage imageWithData:[coder decodeObjectForKey:@"PROFILE_PICTURE"]];
[super decodeRestorableStateWithCoder:coder];

}

State Preservation and Restoration UIImageView added from button event

2 Answers2