What
is Asset Catalog?
Basically you don’t see a large bulk of images in your project navigator and searching any image folder wise one by one.
One more thing to notice, right
click on image set/Asset Catalog and click ‘Show in finder’. In the project
navigator you will find a asset folder corresponding to each images having 1x, 2x
and contents.json
file, describing each image. That file is
automatically created by Xcode.
Types of Assets
There
are three types of assets that can be included in an iOS asset catalog:
App icons - App icon sets contain the icons
that are displayed on the iOS Home screen, Spotlight search results, the
Settings App, and in the App Store.
Launch images - Launch image sets contain all
the versions of the launch image displayed at startup for all of the targeted
iOS devices.
Image sets - Image sets contain all the
versions of an image that are necessary to support all of the targeted iOS
devices. This includes images used in table views, tab bars, image views, and
so on.
Why
to use it?
There are some advantages of
using asset catalogs:
1.)
One of the primary
reasons for using asset catalogs is to make it easier to manage your app's
images.
Suppose if your app supports both retina and
non-retina devices. You need two version of your graphics 1x and 2x and need to
maintain naming convention like, for icon it would be icon.png and icon@2x.png. With asset catalog you no longer need to maintain this
convention.
2.)
A second advantage of
using asset catalogs is performance. If your project has an iOS 7 deployment
target, Xcode compiles your asset catalogs into a runtime binary file format
that improves the speed of your app.
3.)
It also
alleviates the need to keep the naming in sync since they share one name.
How
to create and access it?
App
Icons and Launch Image: Whenever
you create a new project with iOS 7 as deployment target, you will get a folder
in your project navigator named '
'. This is where your App icons and
launch images resides. Tap on it you will get something like this:
'. This is where your App icons and
launch images resides. Tap on it you will get something like this:
Now go to targets of App, At the bottom of the Project Editor, you should see the App Icons and Launch
Images section.
Under App
Icons, there are three sets of images—App, Spotlight,
and Settings that indicate where
each set of icons is used. The Kind
column specifies the device and operating system for which a particular icon is
used. The Dimensions column specifies
the required size of the icon. The Resource
column is intended to show the image included in your project that fits the
criteria in the Dimensions
column. The No image with correct dimensions found
warning is incorrect, since our sample project does contain several of the
required icons.
In the Launch
Images section, there is a list of launch images for the
iPhone.
To add an asset catalog for app icon
and launch images, tap on ‘Use Asset
Catalog button’ at the top. It will display a pop up like this:
Tap on migrate, now your app
will use images present in your ‘Images.xassets’ folder. Your view will get now
updated to
Tap on Arrow on side of
AppIcon/LaunchImage, you will get directed to asset catalogs folder.
Creating
Asset Catalogs: For appicon and
launch images we have built in asset folder, but what for other images that we
are using in our app. Adding this images files to your create a bulk of images
in project navigator, in that case if you want to search for a particular
folder you have to open each and every folder until you are so sure where the
image exactly resides.
Creating Asset catalog escape
us from doing this:
Steps:
1.) Choose File > New > File.
2.) Under iOS or OS X, select Resource.
3.) Select Asset Catalog, and click Next.
4.)
Name the asset
catalog, specify its location, and select the targets.
5.)
Click Create.
Your asset catalogs gets
created. This newly asset catalog is empty for now.
Now it’s your choice, do you
want to maintain images folder wise?
Or, want to add all images
without maintaining folder structure?
Or, want to create separate
asset catalog?
Here I will tell you how to
maintain images folder wise?
Steps:
1.)
Tap on plus(+)
sign at the bottom left corner or right click
2.)
Select ‘New
Folder’
3.)
Your new folder gets
created. Now Select that folder and right on it
4.)
Tap on ‘New Image
Set
5.)
Double tap on the
name of folder and image set to rename it. (Renaming image set is important as
we will be accessing our images by this name only)
6.)
If your images
not already added to your project just drag and drop your images to the block
1x and 2x,your images get added to your project.
Alternatively, if you already added those images in your project, you need to
import those files.
Accessing
Asset Catalog: Accessing
catalogs is same as you are accessing your images with ‘ImageNamed’. To
load an image from an asset catalog, you can call the UIImage:imageNamed:
method, passing the name of the set that contains the image.
For example, if your images set is named as
‘Search, you will access this search images using [UIImage imageNamed:“Search”]
Customizing Sets
Select a image set you want to customize and do
customization like you can change name of your image set or make your images
device specific.
Removing
catalogs, or imagesets, or Folders
To remove a catalog, right
click on that catalog and select ‘Delete’ option.
For imagesets or Folders,
right click or control click on that folders, you will get option ‘Remove
Selected Items’.
Disadvantages: Some few disadvantages when we implement asset
catalog to manage our images are:
1.) You can
no longer Command-Shift-O to look for an image.
2.) Another little annoyance is that Test Flight still wants to see an
Icon.png file in your uploaded apps. The only way around it is to include a
separate icon image in Xcode and add an icon entry back into the plist.
But as these advantages are not bigger than your
App performance, I would recommend to use asset catalogs.
Happy Coding!!
