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Decide When to Update Your Content
To create the illusion of movement in an animation you need to make changes to your content several times per second. That requires you to know when to perform those changes. Ideally, IOS developer want to perform the changes whenever there is a change to be performed but not more often than that. Adding more changes than you need will only spend extra processing time on something that won’t have an effect.
The simplest way to perform the changes is to use a CADisplayLink. The display link sends a message whenever the screen is going to refresh, which allows you to perform changes to your content exactly once per frame. When the animation is finished you can either pause the display link or disable it.
Using a continuous gesture recognizer, like a pan, pinch, or rotation recognizer, is another way to identify when you should perform changes to your content. The gesture recognizer forces IOS developer to accept that you won’t be trying to perform those changes when the user hasn’t moved their finger, and when there aren’t any changes to perform. A more advanced way is to use the scrollViewDidScroll: delegate method of a UIScrollView. We cover how you can tap into gesture recognizers and the UIScrollView behavior later in this article.
Define the Progress of Your Animation
In addition to knowing when to update your content, you need to establish what about your content will actually change and how it will do so over time. The progress of the animation is usually stored as a floating point value in the [0,1] range, where 0 is the initial state and 1 the final state. To determine the progress of your animation you need to establish the following items.The beginning and end of your animation. IOS developer a good idea to normalize the progress of your animation to the [0,1] range. This makes it easier to interpolate properties and more obvious where the animation progress currently is.