Introduction To Animation In Android

Android supports two kinds of animation. 

• One is called "Tweened Animation". 
• The second one is called "Frame by Frame" animation. 

"Tween" is a short for "in-between" borrowed from traditional animators. Inbetweens are drawings that simulate motion between key frames. There may be 24 inbetweens between two key frames or there could be 12 between two key frames. The former case is called "on ones" and the later ones are called "on twos".

In Android here is how "tweening" works. You start with a view. This view can be any view including a view group with any set of complex composed graphical objects. When tweening animation is attached to this view, the animation gets a call back at regular intervals to change any aspect of the tranformation matrix that would be used to render the view.

Moving an object or scaling an object, or changing the shade of an object can all be represented as a set of matrix transformations. By changing this matrix in the call back of the animation you will render the object at a different place with a different scale or a diferent color.

So at a general level, tweening animation is acomplished by changing the properties of a view at various time intervals during the alloted time of an animation.

Android supports the following types of "tween" animations

• AlphaAnimation: Changing Transparency of an object

• RotateAnimation: Rotating an object

• ScaleAnimation: Scale an object

• TranslateAnimation: Move an object

In Android frame by frame animation a series of drawable resources are loaded one after the other. The class AnimationDrawable is responsible for frame by frame animation. Each frame in this animation is a drawable resource.

As you get deeper into Android animation you will see that the distinction is not so clearcut where you can mix both concepts by essentially redrawing the canvas one way or the other.